REFRIGERANT REPORT
This edition supersedes all previous issues.
Refrigerant development and legal situation
Stratospheric ozone depletion as well as atmospheric
greenhouse effect due to refrigerant
emissions have led to drastic changes in
the refrigeration and air conditioning technology index
since the beginning of the 1990s.
This is especially true for the area of commercial
refrigeration and air conditioning
systems with their wide range of applications.
In former years the main refrigerants
used for these systems were ozone depleting
types, namely R12, R22 and R502; for
special applications R114, R12B1, R13B1,
R13 and R503 were used.
The use of these substances is no longer
allowed in industrialised countries, but the
use of R22 has been extended through transitional
periods. However, the European
Union also commited to an early phase-out
for R22, which was enforced in several
stages (see page 8). The main reason for
this early ban of R22 contrary to the international
agreement is the ozone depletion
potential although it is only small.
Since 2010, phase-out regulations became
effective in other countries as well, for
instance in the USA.
This implies enormous consequences for
the whole refrigeration and air conditioning
sector. BITZER therefore committed itself to
taking a leading role in the research and
development of environmentally friendly system
designs.
After the chlorine-free (ODP = 0) HFC refrigerants
R134a, R404A, R407C, R507A and
R410A have become widely established for
many years in commercial refrigeration, air
conditioning and heat pump systems, new
challenges have come up. They concern primarily
the greenhouse effect: The aim is a
clear reduction of direct emissions caused
by refrigerant losses and indirect emissions
by particularly efficient system technology.
In this area, applicable legal regulations are
already in force, such as the EU F-Gas
Regulation No. 517/2014 (BITZER brochure
A-510) and a series of regulations already
ratified or in preparation as part of the EU
Ecodesign Directive (BITZER brochure
A-530). Similar regulations are also in
preparation or already implemented in Australia,
Canada and the USA. On an international
level, the so-called “Kigali Amendment”
was adopted in 2016 under the
Montreal Protocol, in which a step-by-step
reduction of HFCs (“HFC phase-down”) was
agreed upon starting in 2019.
Even though indirect emissions caused by
energy production are considerably higher
than direct (CO2-equivalent) emissions
caused by HFC refrigerants, refrigerants
with high global warming potential (GWP)
will in the future be subject to use restrictions
or bans. This will affect primarily
R404A and R507A, for which alternatives
with lower GWP are already being offered.
However, in order to achieve the legal
objectives, substitutes for further refrigerants
and increased use of naturally occurring
substances (NH3, CO2, hydrocarbons) will
become necessary.
This requires comprehensive testing of
these refrigerants, suitable oils and adjusted
systems. Therefore a close co-operation
exists with scientific institutions, the refrigeration
and oil industries, component manufacturers
as well as a number of innovative
refrigeration and air conditioning companies.
A large number of development tasks have
been completed. Suitable compressors for
alternative refrigerants are available.
Besides the development projects, BITZER
actively supports legal regulations and self
commitments concerning the responsible
use of refrigerants as well as measures to
increase system and components’ efficiency.
The following report deals with potential
measures of a short to medium-term change
towards technologies with reduced environmental
impact in medium and large size
commercial refrigeration and air conditioning
systems. Furthermore, the experiences so
far and the resulting consequences for plant
technology are discussed.
_ _ _
Several studies confirm that vapour compression
refrigeration systems normally
used commercially are far superior in efficiency
to all other processes down to a cold
space temperature of around -40°C.
The selection of an alternative refrigerant
and the system design receives special significance,
however. Besides the request for
substances without ozone depletion potential
(ODP = 0) especially the energy demand
of a system is seen as an essential
criterion due to its indirect contribution to
the greenhouse effect. On top of that there
is the direct global warming potential (GWP)
due to refrigerant emission.
Therefore a calculation method has been
developed for the qualified evaluation of a
system which enables an analysis of the
total influence on the greenhouse effect.
The so-called “TEWI” factor (Total Equivalent
Warming Impact) has been introduced.
Meanwhile, another, more extensive
assessment method has been developed
considering “Eco-Efficiency”. Hereby, both
ecological (such as TEWI) and economical
criteria are taken into account (further
explanations see page 7).
Therefore it is possible that the assessment
of refrigerants with regard to the environment
can differ according to the place of installation
and drive method.
Upon closer evaluation of substitutes for the
originally used CFC and HCFC as well as
for HFCs with higher GWP, the options with
single-substance refrigerants are very limited.
This includes e.g. R134a, which will be
usable for quite some time based on its
comparatively low GWP. Similarly, the
hydro-fluoro-olefins (HFO) R1234yf and
R1234ze(E) with a GWP < 10, which are
also exempted from the F-Gas regulation.
Direct alternatives (based on fluorinated
hydrocarbons) for almost all refrigerants of
higher volumetric refrigerating capacity and
pressure level than R134a can only be “formulated”
as blends. However, taking into
account thermodynamic properties, flammability,
toxicity and global warming potential,
the list of potential candidates is very limited.
Blends of reduced GWP include in addition
to R134a, R1234yf and R1234ze(E) primarily
the refrigerants R32, R125 and
R152a.
Besides halogenated refrigerants, Ammonia
(NH3) and hydrocarbons are considered as
substitutes as well. The use for commercial
applications, however, is limited by strict
safety requirements.
Carbon dioxide (CO2) becomes more important
as an alternative refrigerant and secondary
fluid, too. Due to its specific characteristics,
however, there are restrictions to a
general application.
The following illustrations show a structural
survey of the alternative refrigerants and a
summary of the single or blended substances
which are now available. After that the individual
subjects are discussed.
For refrigerant properties, application
ranges and lubricant specifications, see
pages 41 to 44.
For reasons of clarity the less or only
regionally known products are not specified
in this issue, which is not intended to imply
any inferiority.
3
4
Fig. 1 Structural classification of refrigerants
* Service refrigerants contain HCFC as blend component. They are therefore subject to the same legal regulations as R22 (see page 8).
As a result of the continued refurbishment of older installations, the importance of these refrigerants is clearly on the decline. For some of them, production has already been
discontinued. However, because of the development history of service blends, these refrigerants will continue to be covered in this Report.
Tab. 1 Substitutes for CFC and HCFC refrigerants (chlorine free HFCs)
????
????
Global Warming and
TEWI Factor
As already mentioned (see chapter Refrigerant
developments and legal situation,
page 3), a method of calculation has been
developed to judge the influence upon the
global warming effect for the operation of
individual refrigeration plants (TEWI = Total
Equivalent Warming Impact).
All halocarbon refrigerants (including the
non-chlorinated HFCs) belong to the category
of greenhouse gases. An emission of
these substances contributes to the global
warming effect. The influence is however
much greater in comparison to CO2, which
is the main greenhouse gas in the atmosphere
(in addition to water vapour). Based
on a time horizon of 100 years, the emission
from 1 kg R134a is for example roughly
equivalent to 1430 kg of CO2 (GWP =
1430).
Thus, the reduction of refrigerant losses
must be one of the main tasks for the
future.
On the other hand, the major contributor to
a refrigeration plant’s global warming effect
is the (indirect) CO2 emission caused by
energy generation. Based on the high percentage
of fossil fuels used in power stations,
the average European CO2 release is
around 0.45 kg per kWh of electrical energy.
This results in a significant greenhouse
effect over the lifetime of the plant.
time horizon 100 years
Due to a deciding proportion of the total balance,
there is not only a need for alternative
refrigerants with a favorable (thermodynamic)
energy balance, but an increase in demand
for highly efficient compressors
and associated equipment as well as optimised
system components and system control.
When various compressor designs are compared,
the difference of indirect CO2 emission
(due to the energy requirement) can
have a larger influence upon the total effect
than the refrigerant losses.
A usual formula is shown in Fig. 2. The
TEWI factor can be calculated and the various
areas of influence are correspondingly
separated.
An additional example is shown in Fig. 3
(medium temperature with R134a) shows
Fig. 2 Method for the calculation of TEWI figures
TEWI values with various refrigerant
charges, leakage losses and energy consumptions.
This example is simplified based on an
overall leak rate as a percentage of the
refrigerant charge. The actual values vary
very strongly, so that the potential risk of
individually constructed systems and extensively
branched plants is especially high.
Great effort is taken worldwide to reduce
greenhouse gas emissions, and legal regulations
have partly been developed already.
Since 2007, the “Regulation on certain fluorinated
greenhouse gases” – which also
defines stringent requirements for refrigeration
and air conditioning systems – has
become valid for the EU. Meanwhile, the
revised Regulation No. 517/2014 entered
into force and has to be applied since January
2015.
Environmental aspects
7
Eco-Efficiency
An assessment based on the specific TEWI
value takes into account the effects of global
warming during the operating period of a
refrigeration, air conditioning or heat pump
installation. However, not the entire ecological
and economical aspects are considered.
But apart from ecological aspects, economical
aspects are highly significant when evaluating
technologies and making investment
decisions. With technical systems, the
reduction of environmental impact frequently
involves high costs, whereas low costs
often have increased ecological consequences.
For most companies, the investment
costs are decisive, whereas they are
often neglected during discussions about
minimizing ecological problems.
For the purpose of a more objective assessment,
studies* were presented in 2005 and
2010, using the example of supermarket
refrigeration plants to describe a concept for
evaluating Eco-Efficiency. It is based on
the relationship between added value (a
product’s economic value) and the resulting
environmental impact.
With this evaluation approach, the entire life
cycle of a system is taken into account in
terms of:
o ecological performance in accordance
with the concept of Life Cycle Assessment
as per ISO 14040,
o economic performance by means of a
Life Cycle Cost Analysis.
This means that the overall environmental
impact (including direct and indirect emissions),
as well as the investment costs,
operating and disposal costs, and capital
costs are taken into account.
The studies also confirm that an increase of
Eco-Efficiency can be achieved by investing
in optimized plant equipment (minimized
operating costs). Hereby, the choice of
refrigerant and the associated system technology
play an important role.
Eco-Efficiency can be illustrated in graphic
representation (Example, see Fig. 5). The
results of the Eco-Efficiency evaluation are
shown on the x-axis in the system of coordinates,
whilst the results of the life cycle cost
analysis are shown on the y-axis. This
shows clearly: A system that is situated
higher in the top right quadrant exhibits an
increasingly better Eco-Efficiency – and
conversely, it becomes less efficient in the
bottom left sector.
The diagonals plotted into the system of
coordinates represent lines of equal Eco-
Efficiency. This means that systems or processes
with different life cycle costs and
environmental impacts can quite possibly
result in the same Eco-Efficiency.
.
Environmental aspects
8
Fig. 6 R12/R22 – comparison of discharge gas temperatures of
a semi-hermetic compressor
Fig. 7 R12/R22/R502 – comparison of pressure levels
refrigerant in new systems and for service
purposes due to its ozone depletion potential
– although being low.
With regard to components and system
technology a number of particularities are to
follow as well. Refrigerant R22 has approximately
55% higher refrigerating capacity and
pressure levels than R12**. The significantly
higher discharge gas temperature is also a
critical factor compared to R12 (Fig. 6) and
R502**.
Similar relationships in terms of thermal load
are found in the comparison with HFC refrigerants
R134a, R404A/R507A (pages 9 and 17).
Resulting design criteria
Particularly critical – due to the high discharge
gas temperature – are low temperature
plants especially concerning thermal
stability of oil and refrigerant, with the danger
of acid formation and copper plating.
Special measures have to be adopted
therefore, such as two stage compression,
controlled refrigerant injection, additional
cooling, monitoring of discharge gas temperature,
limiting the suction gas superheat
and particularly careful installation.
* Not allowed for new equipment in Germany and
Denmark since January 1st, 2000 and in Sweden
as of 1998.
Since January 1st, 2001 restrictions apply to the
other member states of the EU as well. The measures
concerned are defined in the ODS Regulation
1005/2009 of the EU commision on ozone depleting
substances amended in 2009. This regulation also
governs the use of R22 for service reasons within
the entire EU.
Since 2010, phase-out regulations in other countries,
such as the USA, are valid.
R22 as transitional refrigerant
Although chlorine-free refrigerants, such as
R134a and R404A/R507A (Fig. 1 and Tab.
1) have been widely used − but are already
being replaced by alternatives with lower
GWP in the EU for example − R22 is still
used internationally in many areas, both for
new installations and for retrofitting existing
ones.
Reasons are relatively low investment costs,
especially compared with R134a systems,
but also its large application range, favourable
thermodynamic properties and low
energy requirement. Additionally, R22 and
components are available world wide, which
is not guaranteed everywhere for the chlorine
free alternatives.
Despite of the generally favourable properties
R22 is already subject to various regional
restrictions* which control the use of this
HCFC refrigerants
There are also limitations in the application
with low evaporating temperatures to be
considered.
Comprehensive tests have demonstrated
that the performance of R134a exceeds theoretical
predictions over a wide range of
compressor operating conditions. Temperature
levels (discharge gas, oil) are even
lower than with R12 and, therefore, substantially
lower than R22 values. There are
thus many potential applications in air conditioning
and medium temperature refrigeration
plants as well as in heat pumps. Good
heat transfer characteristics in evaporators
and condensers (unlike zeotropic blends)
favour an economical use.
R134a is also characterized by a comparably
low GWP (1430). Therefore, in view of
future restrictions (for example EU F-Gas
Regulation), the use of this refrigerant will
still be possible for quite some time. If
required, systems can later be converted
relatively easily to non-flammable (A1)
HFO/HFC alternatives with a GWP of
approx. 600 (pages 24/25).
Lubricants for R134a and other HFCs
The traditional mineral and synthetic oils are
not miscible (soluble) with R134a and other
HFCs described in the following and are
therefore only insufficiently transported
around the refrigeration circuit.
Immiscible oil can settle out in the heat
exchangers and prevent heat transfer to
such an extent that the plant can no longer
be operated.
New lubricants were developed with the
appropriate solubility and have been in use
for many years. These lubricants are based
on Polyol Ester (POE) and Polyalkylene
Glycol (PAG).
For further explanations on lubricants see
chapter “Lubricants for compressors”, page
40.
R134a as substitute for
R12 and R22
R134a was the first chlorine free (ODP = 0)
HFC refrigerant that was tested comprehensively.
It is now used world-wide in many
refrigeration and air conditioning units with
good results. As well as being used as a
pure substance, R134a is also applied as a
component of a variety of blends (see also
“Refrigerant blends”, page 13).
R134a has similar thermodynamic
properties to R12:
Refrigerating capacity, energy demand,
temperature properties and pressure levels
are comparable, at least in air conditioning
and medium temperature refrigeration
plants. This refrigerant can therefore be
used as an alternative for most former R12
applications.
For some applications R134a is even preferred
as a substitute for R22, an important
reason being the limitations to the use
of R22 in new plants and for service. However,
the lower volumetric refrigerating
capacity of R134a (Fig. 9) requires a larger
compressor displacement than with R22.
HFC refrigerants
10
Supplementary BITZER information
concerning the use of R134a
(see also http://www.bitzer.de)
o Technical Information KT-620
“HFC Refrigerant R134a”
o Technical Information KT-510
„Polyolester oils for reciprocating
compressors“
o Special edition
„A new generation of compact screw
compressors optimised for R134a“
Resulting design and construction
criteria
Suitable compressors are required for
R134a with a special oil charge and adapted
system components. The normal metallic
materials used in CFC plants have also
been proven with ester oils; elastomers
must sometimes be matched to the changing
situation. This is especially valid for flexible
hoses where the requirements call for a
minimum residual moisture content and low
permeability.
The plants must be dehydrated with particular
care and the charging or changing of
lubricant must also be done carefully. In
addition relatively large driers should be
provided, which have also to be matched to
the smaller molecule size of R134a.
Meanwhile, many years of very positive
experience with R134a and ester oils
have been accumulated. For this refrigerant,
BITZER offers an unequalled
wide range of reciprocating, screw and
scroll compressors.
Converting existing R12 plants to
R134a
At the beginning this subject was discussed
very controversially, several conversion
methods were recommended and applied.
Today there is a general agreement on
technically and economically matching solutions.
The characteristics of ester oils are very
favourable here: Under certain conditions
they can be used with CFC refrigerants,
they can be mixed with mineral oils and tolerate
a proportion of chlorine up to a few
hundred ppm in an R134a system.
The remaining moisture content has, however,
an enormous influence. Very thorough
evacuation (removal of remaining chlorine
and dehydration) is therfore essential, as
well as the installation of generously dimensioned
driers. There is doubtful experience
with systems where the chemical stability
was already insufficient with R12 operation
e.g. with bad maintenance, small drier
capacity, high thermal loading. Increased
deposition of oil decomposition products
containing chlorine is found often. These
products are released by the influence of
the highly polarized mixture of ester oil and
R134a and find their way into the compressor
and control devices. Conversion should
therefore be limited to systems which are in
a good condition.
Restrictions for R134a in mobile
air conditioning (MAC) systems
An EU Directive on “Emissions from MAC
systems” bans the use of R134a in new
systems. Various alternative technologies
are already in use. For further explanation
see pages 11, 12, and 36.
HFC refrigerants
11
Alternatives to R134a
For mobile air conditioning systems (MAC)
with open drive compressors and hose connections
in the refrigerant circuit, the risk of
leakages is considerably higher than with
stationary systems. An EU Directive
(2006/40/EC) has been passed to reduce
direct emissions in this application area.
Within the scope of the Directive, and starting
2011, type approvals for new vehicles
will only be granted if they use refrigerants
with a global warming potential (GWP) of
less than 150. Consequently, this excludes
R134a (GWP = 1430) which has been used
so far in these systems.
Meanwhile, alternative refrigerants and new
technologies were developed and tested.
This also involved a closer examination of
the use of R152a.
For quite some time the automotive industry
has agreed on so-called “Low GWP” refrigerants.
The latter is dealt with as follows.
CO2 technology, favored for this application
for quite some time, has not been widely
implemented for a variety of reasons (see
also pages 12 and 36).
R152a – an alternative
to R134a (?)
R152a is very similar to R134a with regard
to volumetric refrigerating capacity (approx.
-5%), pressure levels (approx. -10%) and
energy efficiency. Mass flow, vapour density
and thus also the pressure drop are even
more favourable (approx. -40%).
R152a has been used for many years as a
component in blends, but not as a single
substance refrigerant till now. Especially
advantageous is the very low global warming
potential (GWP = 124).
R152a is flammable – due to its low fluorine
content – and classified in safety group A2.
As a result, increased safety requirements
demand individual design solutions and
safety measures along with the corresponding
risk analysis.
For this reason, the use of R152a in mobile
air conditioning systems for passenger cars
(MAC) has not been implemented yet.
“Low GWP” HFO refrigerant
R1234yf
The ban on the use of R134a in mobile air
conditioning systems within the EU has triggered
a series of research projects. In addition
to CO2 technology (see chapter CO2 in
mobile air conditioning systems, page 36),
refrigerants with very low GWP values and
similar thermodynamic properties as R134a
have been developed.
In early 2006, two refrigerant mixtures were
introduced under the names “Blend H”
(Honeywell) and “DP-1” (DuPont). INEOS
Fluor followed with another version under
the trade name AC-1. In the broadest
sense, all of these refrigerants were blends
of various fluorinated molecules.
During the development and test phase it
became obvious that not all acceptance
criteria could be met, and thus further
examinations with these blends were discontinued.
Consequently, DuPont (meanwhile
Chemours) and Honeywell bundled their
research and development activities in a
joint venture which focused on 2,3,3,3-
tetrafluoropropene (CF3CF=CH2). This
refrigerant, designated R1234yf, belongs to
the group of hydro fluoro olefins (HFO).
These refrigerants are unsaturated HFCs
with a chemical double bond.
HFC refrigerants
12
With view to the relatively simple conversion
of mobile air conditioning systems, this
technology prevailed up to now over the
competing CO2 systems.
However, as already explained before, due
to the flammability of R1234yf, investigations
focus on other technical solutions.
This includes active fire-extinguishing devices
(e.g. with argon), but also enhancements
of CO2 systems.
For detailed information on properties and
the application, see chapter “Low GWP”
HFOs and HFO/HFC blends as alternatives
to HFCs, page 24.
Toxicity investigations have shown very
positive results, as well as compatibility
tests of the plastic and elastomer materials
used in the refrigeration circuit. Some lubricants
show increased chemical reactivity
which, however, can be suppressed by a
suitable formulation and/or addition of
“stabilizers”.
Operating experiences gained from laboratory
and field trials to date allow a positive
assessment, particularly with regard to performance
and efficiency behaviour. For the
usual range of mobile air conditioning operation,
refrigerating capacity and coefficient
of performance (COP) are within a range of
5% compared with that of R134a. Therefore,
it is expected that simple system modifications
will provide the same performance
and efficiency as with R134a.
The critical temperature and pressure levels
are also similar, while the vapour densities
and mass flows are approximately 20%
higher. The discharge gas temperature with
this application is up to 10 K lower.
The global warming potential is extremely
low (GWP = 4). When released to the atmosphere,
the molecule rapidly disintegrates
within a few days, resulting in a very low
GWP. This raises certain concerns regarding
the long-term stability in refrigeration circuits
under real conditions.
However, extensive testing has demonstrated
the required stability for mobile air conditioning
systems.
R1234yf has lower flammability as measured
by ASTM 681, but requires significantly
more ignition energy than R152a, for
instance. Due to its low burning velocity and
the high ignition force, it received a classification
of the new safety group “A2L” according
to ISO 817.
In extensive test series, it has been shown
that a potentially increased risk of the refrigerant
flammability in MAC systems can be
avoided by implementing suitable constructive
measures. However, some investigations
(e.g. by Daimler) also show an increased
risk. This is why various manufacturers
have intensified again the development
of alternative technologies.
HFC refrigerants
13
Refrigerant blends
Refrigerant blends have been developed for
existing as well as for new plants with properties
making them comparable alternatives
to the previously used substances.
It is necessary to distinguish between three
categories:
- Transitional or service blends
which mostly contain HCFC R22 as the
main constituent. They are primarily
intended as service refrigerants for
older plants with view on the use ban of
R12, R502 and other CFCs. Corresponding
products are offered by various manufacturers,
there is practical experience
covering the necessary steps of conversion
procedure.
However, the same legal requirements as
for R22 apply to the use and phase-out of
these blends (see page 8).
- HFC blends
These are substitutes for the refrigerants
R502, R22, R13B1 and R503. Above all,
R404A, R507A, R407C and R410A, are
being used to a great extent.
One group of these HFC blends also contains
hydrocarbon additives. The latter
exhibit an improved solubility with lubricants,
and under certain conditions they
allow the use of conventional oils. In many
cases, this permits the conversion of existing
(H)CFC plants to chlorine-free refrigerants
(ODP = 0) without the need for an oil
change.
- HFO/HFC blends
as successor generation of HFC refrigerants.
It concerns blends of new “Low
GWP” refrigerants (e.g. R1234yf) with
HFCs. The fundamental target is an additional
decrease of the global warming potential
(GWP) as compared to established
halogenated substances (see page 24).
Blends of two and three components already
have a long history in the refrigeration trade.
A difference is made between the so called
“azeotropes” (e.g. R502, R507A) with thermodynamic
properties similar to single substance
refrigerants, and “zeotropes” with
“gliding” phase changes (also see next
chapter). The original development of
“zeotropes” mainly concentrated on special
applications in low temperature and heat
pump systems. Actual system construction,
however, remained the exception.
A somewhat more common earlier practice
was the mixing of R12 to R22 in order to
improve the oil return and to reduce the discharge
gas temperature with higher pressure
ratios. It was also usual to add R22 to
R12 systems for improved performance, or
to add hydrocarbons in the extra low temperature
range for a better oil transport.
This possibility of specific “formulation” of
certain characteristics was indeed the basis
for the development of a new generation of
blends.
At the beginning of this Report (see chapter
Refrigerant developments and legal situation,
page 3) it was already explained that
no direct single-substance alternatives (on
the basis of fluorinated hydrocarbons) exist
for the previously used and current refrigerants
of higher volumetric refrigeration capacity
than R134a. This is why they can only
be “formulated” as blends. However, taking
into account thermodynamic properties,
flammability, toxicity and global warming
potential, the list of potential candidates is
strongly limited.
For the previously developed CFC and
HCFC substitutes, the range of substances
was still comparably large, due to the fact
that substances of high GWP could also be
used. However, for formulating blends with
significantly reduced GWP, in addition to
R134a, R1234yf and R1234ze(E), primarily
refrigerants R32, R125 and R152a can be
used. Most of them are flammable. They
also exhibit considerable differences with
respect to their boiling points, which is why
all “Low GWP” blends of high volumetric
refrigerating capacity have a substantial
temperature glide (see next chapter).
BITZER has accumulated extensive
experience with refrigerant blends.
Laboratory and field testing was commenced
at an early stage so that basic
information was obtained for the optimizing
of the mixing proportions and
for testing suitable lubricants. Based
on this data, a large supermarket plant
– with 4 BITZER semi-hermetics in parallel
– could already be commissioned
in 1991. The use of these blends in the
most varied systems has been state-ofthe-
art for many years – generally with
good experiences.
General characteristics of zeotropic
blends
As opposed to azeotropic blends (e.g.
R502, R507A), which behave as single substance
refrigerants with regard to evaporation
and condensing processes, the phase
change with zeotropic fluids occurs in a
“gliding” form over a certain range of temperature.
This “temperature glide” can be more or
less pronounced, it depends mainly on the
boiling points and the percentage proportions
of the individual components. Certain
supplementary definitions are also used,
depending on the effective values, such as
“near-azeotrope” or “semiazeotrope” for
less than 1 K glide.
Essentially, this results in a small temperature
increase already in the evaporation
phase and a reduction during condensing.
In other words: At a certain pressure level,
the resulting saturation temperatures differ
in the liquid and vapour phases (Fig. 11).
To enable a comparison with single substance
refrigerants, the evaporating and
condensing temperatures have been often
defined as mean values. As a consequence
the measured subcooling and
superheating conditions (based on mean
values) are unrealistic. The effective difference
– based on dew and bubble temperature
– is less in each case. These factors
are very important when assessing the minimum
superheat at the compressor inlet
(usually 5 to 7 K) and the quality of the
refrigerant after the liquid receiver.
Refrigerant blends
With regard to a uniform and easily comprehensible
definition of the rated compressor
capacity, the revised standards EN 12900
and AHRI540 are applied. Evaporating and
condensing temperatures refer to saturated
conditions (dew points).
o Evaporating temperature according to
point A (Fig. 11)
o Condensing temperature according to
point B (Fig. 11)
In this case the assessment of the effective
superheat and subcooling temperatures will
be simplified.
It must however be considered that the
actual refrigerating capacity of the system
can be higher than the rated compressor
capacity. This is partly due to an effectively
lower temperature at the evaporator inlet.
A further characteristic of zeotropic refrigerants
is the potential concentration shift
when leakage occurs. Refrigerant loss in
the pure gas and liquid phases is mainly
non-critical. Leaks in the phase change
areas, e.g. after the expansion valve, within
the evaporator and condenser/receiver are
considered more significant. It is therefore
recommended that soldered or welded
joints should be used in these sections.
Extended investigations have shown in the
meantime that leakage leads to less serious
changes in concentration than initially
thought. In any case it is certain that the following
substances of safety group A1 (see
page 41) which are dealt with here cannot
develop any flammable mixtures, either
inside or outside the circuit. Essentially similar
operating conditions and temperatures
as before can be obtained by supplementary
charging with the original refrigerant in
the case of a small temperature glide.
Further conditions/recommendations concerning
the practical handling of blends
must also be considered:
o The plant always has to be charged with
liquid refrigerant. When vapour is taken
from the charging cylinder, concentration
shifts may occur.
o Since all blends contain at least one
flammable component, the entry of air
into the system must be avoided. If the
proportion of air is too high, a critical shift
of the ignition point can occur under high
pressure and while evacuating.
o The use of blends with a significant temperature
glide is not recommended for
plants with flooded evaporators. A large
concentration shift is to be expected in
this type of evaporator, and as a result
also in the circulating refrigerant mass
flow.
Refrigerant blends
15
Service blends with the basic
component R22* as substitutes
for R502
As a result of the continued refurbishment
of older installations, the importance of
these refrigerants is clearly on the decline.
For some of them, production has already
been discontinued. However, because of
the development history of service blends,
these refrigerants will continue to be covered
in this Report.
These refrigerants belong to the group of
“Service blends” and have been offered
under the designations R402A/R402B*
(HP80/HP81 – DuPont), R403A/R403B*
(formerly ISCEON® 69S/69L) and R408A*
(“Forane®” FX10 – Arkema).
The basic component is in each case R22,
the high discharge gas temperature of
which is significantly reduced by the addition
of chlorine free substances with low
isentropic compression exponent (e.g.
R125, R143a, R218). A characteristic feature
of these additives is an extraordinarily
high mass flow, which enables the mixture
to achieve a great similarity to R502.
R290 (Propane) is added as the third component
to R402A/B and R403A/B to improve
miscibility with traditional lubricants
as hydrocarbons have especially good solubility
characteristics.
For these blends two variations are offered
in each case. When optimizing the blend
variations with regard to identical refrigerating
capacity as for R502 the laboratory
measurements showed a significantly increased
discharge gas temperature (Fig. 13),
which above all, with higher suction gas
superheat (e.g. supermarket use) leads to
limitations in the application range.
On the other hand a higher proportion of
R125 or R218, which has the effect of reducing
the discharge gas temperature to the
level of R502, results in somewhat higher
refrigerating capacity (Fig. 14).
With regard to material compatibility the
blends can be judged similarly to (H)CFC
refrigerants. The use of conventional refrigeration
oil (preferably semi or full synthetic)
is also possible due to the R22 and
R290 proportions.
Apart from the positive aspects there are
also some disadvantages. These substances
are alternatives only for a limited time.
The R22 proportion has (although low) an
ozone depletion potential. Furthermore, the
additional components R125, R143a and
R218 have a high global warming potential
(GWP).
Resulting design criteria/
Converting existing R502 plants
The compressor and the components which
are matched to R502 can remain in the system
in most cases. The limitations in the
application range must however be considered:
Higher discharge gas temperature
than R502 with R402B**, R403A** and
R408A** or higher pressure levels with
R402A** and R403B**.
The good solubility characteristics of R22
and R290 increase the risk that, after conversion
of the plant, possible deposits of oil
decomposition products containing chlorine
are dissolved and find their way into the
compressor and control devices. Systems
where chemical stability was already insufficient
with R502 operation (bad maintenance,
low drier capacity, high thermal
loading) are particularly at risk.
Thus, generously dimensioned suction gas
filters and liquid line driers should be installed
for cleaning before conversion, and
an oil change should be made after approximately
100 hours operation. Further checks
are recommended.
* When using blends containing R22 legal regulations
are to be observed, see page 8.
** Classification according to ASHRAE nomenclature.
Fig. 13 Effect of the mixture variation upon the discharge
gas temperature (example: R22/R218/R290)
Fig. 14 Comparison of the performance data of a semi-hermetic
compressor
???????????
Service blends
16
The operating conditions with R502 (including
discharge gas temperature and suction
gas superheat) should be noted so that a
comparison can be made with the values
after conversion. Depending upon the
results, control devices should possibly be
reset and other additional measures should
be taken as required.
Service blends as
substitutes for R12 (R500)
Although (as experience already shows)
R134a is also well suited for the conversion
of existing R12 plants, the general use for
such a “retrofit” procedure is not always
possible. Not all compressors which have
previously been installed are designed for
the application with R134a. In addition a
conversion to R134a requires the possibility
to make an oil change, which is for example
not the case with most hermetic type compressors.
Economical considerations also arise, especially
with older plants where the effort of
converting to R134a is relatively high. The
chemical stability of such plants is also
often insufficient and thus the chance of
success is very questionable.
Therefore “Service blends” are also available
for such plants as an alternative to R134a
and are offered under the designations
R401A/R401B, R409A. The main components
are the HCFC refrigerants R22, R124
and/or R142b. Either HFC R152a or R600a
(Isobutane) is used as the third component.
Operation with traditional lubricants (preferably
semi or full synthetic) is also possible
due to the major proportion of HCFC.
A further service blend was offered under
the designation R413A (ISCEON® 49 –
DuPont), but replaced by R437A by the end
of 2008. However, because of the development
history of service blends, R413A will
continue to be covered in this Report. The
constituents of R413A consist of the chlorine
free substances R134a, R218, and
R600a. In spite of the high R134a content,
the use of conventional lubricants is possible
because of the relatively low polarity
of R218 and the favourable solubility of
R600a.
R437A is a blend of R125, R134a, R600
and R601 with similar performance and
properties as R413A. This refrigerant also
has zero ODP.
However, due to the limited miscibility of
R413A and R437A with mineral and alkylbenzene
oils, oil migration may result in
systems with a high oil circulation rate
and/or a large liquid volume in the receiver
– for example if no oil separator is installed.
If insufficient oil return to the compressor is
observed, the refrigerant manufacturer
recommends replacing part of the original
oil charge with ester oil. But from the compressor
manufacturer’s view, such a measure
requires a very careful examination of
the lubrication conditions. For example, if
increased foam formation in the compressor
crankcase is observed, a complete change
to ester oil will be necessary. Moreover,
under the influence of the highly polarized
blend of ester oil and HFC, the admixture of
or conversion to ester oil leads to increased
dissolving of decomposition products and
dirt in the pipework. Therefore, generously
dimensioned suction clean-up filters must
be provided. For further details, see the
refrigerant manufacturer’s “Guidelines”.
Resulting design criteria/
Converting existing R12 plants
Compressors and components can mostly
remain in the system. However, when using
R413A and R437A the suitability must be
checked against HFC refrigerants. The
actual “retrofit” measures are mainly restricted
to changing the refrigerant (possibly
oil) and a careful check of the superheat
setting of the expansion valve.
A significant temperature glide is present
due to the relatively large differences in the
boiling points of the individual substances,
which requires an exact knowledge of the
saturation conditions (can be found from
vapour tables of refrigerant manufacturer
and in the BITZER Refrigerant App) in order
to assess the effective suction gas superheat.
In addition the application range must also
be observed. Different refrigerant types are
required for high and low evaporating temperatures
or distinct capacity differences
must be considered. This is due to the
steeper capacity characteristic, compared to
R12.
Due to the partially high proportion of R22
especially with the low temperature blends,
the discharge gas temperature with some
refrigerants is significantly higher than with
R12. The application limits of the compressor
should therefore be checked before
converting.
The remaining application criteria are similar
to those for the substitute substances for
R502 which have already been mentioned.
* By using R22 containing blends the legal requirements
are to be followed, see chapter R22 as transitional
refrigerant, page 8.
Service blends
17
R404A and R507A as
substitutes for R22 and R502
These blends are chlorine free substitutes
(ODP = 0) for R22 as well as for R502 in
medium and low temperature ranges.
A composition which was already launched
at the beginning of 1992 is known under the
trade name Suva® HP62 (DuPont). Long
term use has shown good results. Further
blends were traded as Forane® FX70
(Arkema) and Genetron® AZ50 (Allied Signal/
Honeywell) or Solkane® 507 (Solvay).
HP62 and FX70 have been listed in the
ASHRAE nomenclature as R404A and
AZ50 as R507A.
The basic components belong to the HFC
group, where R143a belongs to the flammable
category. Due to the combination
with a relatively high proportion of R125
the flammability is effectively counteracted,
even in the case of leakage.
A feature of all three ingredients is the very
low isenropic compression exponent which
results in a similar, with even a tendency to
be lower, discharge gas temperature to
R502 (Fig. 15). The efficient application of
single stage compressors with low evaporating
temperatures is therefore guaranteed.
Due to the similar boiling points for R143a
and R125, with a relatively low proportion of
Fig. 15 R404A/R502 – comparison of discharge gas temperatures of a
semi-hermetic compressor
Fig. 16 Comparison of performance data of a semi-hermetic
compressor
R134a, the temperature glide with the ternary
blend R404A within the relevant application
range is less than one Kelvin. The
characteristics within the heat exchangers
are therefore not very different than with
azeotropes. The results obtained from heat
transfer measurements show favourable
conditions.
R507A is a binary substance combination
which even gives an azeotropic characteristic
over a relatively wide range. The conditions
therefore tend to be even better.
The performance (Fig. 16) gives hardly any
difference between the various substances
and ist very similar to R502. This also
explains the high market penetration of
these refrigerants. With regard to the thermodynamic
properties, they are particularly
suitable for commercial medium and low
temperature systems.
Typical metallic materials are compatible
with HFC refrigerants. Elastomers, however,
must be adapted to the changed characteristics.
Suitable lubricants are polyol esters
(see chapter Lubricants for compressors,
page 40).
The relatively high global warming potential
(GWP = 3922 .. 3985), which is mainly
determined by the R143a and R125, is
something of a hitch. However, it is better
than R502 and with regard to the favourable
energy demand also leads to a reduction of
the TEWI value. Other improvements are
possible in this respect due to further developed
system control.
Nevertheless, due to their high global warming
potential (GWP), the use of R404A and
R507A will no longer be allowed in the EU
in new installations from 2020. This has
been settled in the F-Gas Regulation No.
517/2014 to be applied since 2015. However,
the current requirement of phase-down
in connection with a strict quota system will
lead to an earlier phase-out in many applications.
For more detailed information,
please refer to BITZER brochure A-510.
In the USA, Canada and Australia there are
also requirements to phase-out R404A and
R507A. For an international phase-down
(starting in 2019) of HCFC and HFC refrigerants,
the so-called Kigali Amendment was
agreed upon in 2016 as part of the Montreal
Protocol.
Alternatives with lower GWP are the HFC
blends explained in the following (from page
18), as well as HFO/HFC blends being developed
and evaluated (from page 24).
Halogen free refrigerants or cascade
systems using different refrigerants are
also an option for specific applications
(from page 28).
Substitutes for R22 in refrigeration systems
18
R407A/407B/407F/407H as
substitutes for R22 and R502
As an alternative to the earlier described
substitutes, additional mixtures have been
developed based on R32 which is chlorine
free (ODP = 0) and flammable like R143a.
The refrigerant R32 is also of the HFC type
and initially was regarded as a main candidate
for R22 alternatives (page 20). However,
due to extent of blend variations comparable
thermodynamic characteristics to
R404A/R507A can also be obtained.
These kind of refrigerants were marketed at
first under the trade name KLEA® 60/61
(ICI) and are listed as R407A/R407B* in the
ASHRAE nomenclature.
Honeywell has developed another blend
with the trade name Performax® LT (R407F
according to ASHRAE nomenclature) and
introduced it into the market, similar Daikin
Chemical with R407H. For both blends, the
R32 proportion is higher than for R407A,
while the R125 proportion is lower. With
R407H, this results in certain restrictions for
low temperature applications.
However, the necessary conditions for alternatives
containing R32 are not quite as
favourable compared to the R143a based
substitutes discussed earlier. The boiling
point of R32 is very low at -52°C, in addition
the isentropic compression exponent is
even higher than with R22. Rather high proportions
of R125 and R134a are necessary
to match the characteristics at the level of
R404A and R507A. The flammability of R32
is thus effectively suppressed, but the large
differences in boiling points with a high proportion
of R134a lead to a larger temperature
glide.
The main advantage of R32 is the extraordinarily
low global warming potential (GWP =
675), so that even in combination with R125
and R134a it is significantly lower than with
the R143a based alternatives mentioned
above (R407A: GWP = 2107, R407F: GWP
= 1825, R407H: GWP = 1490).
Thus, they also comply with the requirement
of the new EU F-Gas Regulation
which from 2020 will only allow refrigerants
of GWP < 2500.
Measurements made with R32 containing
blends do show certain capacity reductions
compared to R404A and R507A, with low
evaporating temperatures. The COP however
shows less deviation and is even higher
in medium temperature applications (Fig. 18).
* Meanwhile, R407B is no longer available in the market.
Due to the historical development of HFC blends
this refrigerant will, however, still be considered in
this Report.
Resulting design criteria
The system technology can be based on
the experience with R22 and R502 over a
wide area.
On the thermodynamic side, a heat exchanger
between the suction and liquid
line is recommended as this will improve
the refrigerating capacity and COP.
BITZER offers the whole program of
reciprocating, scroll and screw compressors
for R404A and R507A.
Supplementary BITZER information concerning
the use of HFC blends
(see also http://www.bitzer.de)
o Technical Information KT-651
„Retrofitting of R22 systems to
alternative refrigerants”
o Technical Information KT-510
„Polyolester oils for reciprocating
compressors“
Fig. 17 R407A, R407F/R404A – comparison of discharge gas temperature of a
semi-hermetic compressor
Fig. 18 Comparison of performance data of a semi-hermetic
compressor
????
Sub s ti tut e s fo r R22 in r e fr ige rat io n s yst e ms
19
Whether these favourable conditions are
confirmed in real applications is subject to
the system design. An important factor is
the significant temperature glide, which can
have a negative influence upon the capacity/
temperature difference of the evaporator
and condenser.
With regard to the material compatibility,
R32 blends can be assessed similarly to
R404A and R507A; the same applies to the
lubricants.
Despite the relatively high proportion of
R125 and R134a in the R32 blends, the discharge
gas temperature is higher than with
the R143a based alternatives (especially for
R407F and even to a higher degree with
R407H). This results in certain limitations in
the application range as well as the requirement
for additional cooling of compressors
when operating at high pressure ratios.
2-stage compressors can be applied very
efficiently where especially large lift conditions
are found. An important advantage in
this case is the use of a liquid subcooler.
Resulting design criteria
The experience with R404A/R507A and
R22 can be used for plant technology in
many respects, although the temperature
glide as well as the difference in the thermodynamic
properties have to be considered.
This especially concerns the design
and construction of heat exchangers and
expansion valves.
Converting existing R22 plants to
R407A/407B/407F/407H
Practical experiences show that qualified
conversions are possible. Compared to R22
the volumetric refrigeration capacity is nearly
similar while the refrigerant mass flow is
only slightly higher. These are relatively
favourable conditions for the conversion of
medium and low temperature R22 systems.
The main components can remain in the
system provided that they are compatible
with HFC refrigerants and ester oils.
However, special requirements placed on
the heat exchanger with regard to the significant
temperature glide must be considered.
A conversion to ester oil is also necessary,
which leads to increased dissolving of decomposition
products and dirt in the
R422A as substitute
for R22 and R502
Amongst other aims, R422A (ISCEON®
MO79 – Chemours) was developed in order
to obtain a chlorine-free refrigerant (ODP = 0)
for the simple conversion of existing medium
and low temperature refrigeration
systems using R22 and R502.
For this, it was necessary to formulate a
refrigerant with comparable performance
and energy efficiency to that of R404A,
R507A, and R22, which also permits the
use of conventional lubricants.
R422A is a zeotropic blend of the basic
components R125 and R134a with a small
addition of R600a. Due to its relatively high
R134a percentage, the temperature glide
(see chapter Refrigerant Properties, page
42) lies higher than for R404A, but lower
than other refrigerants with the same component
blends – such as R417A and R422D
(see page 22).
The adiabatic exponent, and therefore also
the discharge gas and oil temperatures of the
compressor, are lower than for R404A and
R507A. At extremely low temperatures, this
can be advantageous. However, in cases of
low pressure ratio and suction gas superheat,
this can be a disadvantage due to increased
refrigerant solution if ester oil is used.
The material compatibility is comparable to
the blends mentioned previously, the same
applies to the lubricants. On account of the
good solubility of R600a, conventional lubricants
can also be used under favourable
circumstances.
In particular, advantages result during the
conversion of existing R22 and R502
systems as mentioned above. However, for
plants with high oil circulation rates and/or
large liquid charge in the receiver, oil migration
might occur – for example if no oil
separator is installed.
If insufficient oil return to the compressor is
observed, the refrigerant manufacturer
recommends replacing part of the original
oil charge with ester oil. But from the compressor
manufacturer’s view, such a measure
requires a very careful examination of
the lubrication conditions. For example, if increased
foam formation in the compressor
crankcase is observed, a complete change
to ester oil* will be necessary. Under the
influence of the highly polarized blend of
ester oil and HFC, the admixture of or conversion
to ester oil leads to increased dissolving
of decomposition products and dirt
in the pipework. Therefore, generously
dimensioned suction clean-up filters must
be provided. For further details, see the
refrigerant manufacturer’s “Guidelines”.
From a thermodynamic point of view, a heat
exchanger between suction and liquid line
is recommended, improving the refrigerating
capacity and coefficient of performance. Besides
this the resulting increase in operating
temperatures leads to more favourable
lubricating conditions (lower solubility).
Due to the high global warming potential
(GWP ≥ 2500), R422A will no longer be
allowed for new installations in the EU from
2020 onwards. The requirements and restrictions
are specified in the F-Gas Regulation
517/2014.
* General proposal for screw compressors and liquid
chillers when used with DX evaporators with internally
structured heat exchanger tubes. Furthermore, an
individual check regarding possible additional measures
will be necessary.
BITZER compressors are suitable for
R422A. An individual selection is possible
upon demand.
pipework. Therefore, generously dimensioned
suction clean-up filters must be provided.
Conversion of existing R404A/R507A
systems to R407A/407B/407F/407H
Larger differences in thermodynamic properties
(e.g. mass flow, discharge gas temperature)
and the temperature glide of
R407A/F/H may require the replacement of
control components and if necessary
retrofitting of additional compressor cooling
when existing systems are converted.
For newly built systems, a specific design
of components and system is necessary.
BITZER offers a comprehensive program
of reciprocating and screw compressors
for R407A und R407F. An individual
selection of compressors for R407H is
possible upon demand.
Substitutes for R22 in refrigeration systems
Fig. 19 R407C/R22 – comparison of performance data of a semi-hermetic
compressor
Fig. 20 R407C/R22 – comparison of pressure levels
Thus, R407C also complies with the requirement
of the new EU F-Gas Regulation
which from 2020 onwards will only
allow refrigerants with GWP < 2500. However,
the quantity limitation through the
“phase-down” will also lead to significantly
restricted availability.
The high temperature glide is a disadvantage
for usual applications which requires
appropriate system design and can have a
negative influence on the efficiency of the
heat exchangers (see chapter General characteristics
of zeotropic blends, page 13).
Due to the properties mentioned, R407C is
preferably an R22 substitute for air conditioning
and heat pump systems and (within
certain limitations) also for medium temperature
refrigeration. In low temperature
refrigeration, because of the high proportion
of R134a, a significant drop in refrigerating
capacity and COP is to be expected. There
is also the danger of an increased R134a
concentration in the blend in evaporators,
with reduced performance and malfunctioning
of the expansion valve (e.g. insufficient
suction gas superheat).
Material compatibility is similar to that of the
blends discussed previously; the same applies
to lubricants.
* Previous trade names are not used any more.
R407C as substitute
for R22
Mixtures of HFC refrigerants R32, R125 and
R134a were considered to be the preferred
candidates for short-term substitutes for
R22 in the EU in view of the early ban of
R22. Performance values and efficiency are
highly comparable (Fig. 19). At first two
blends of the same composition have been
introduced under the trade names AC9000*
(DuPont) and KLEA® 66* (ICI). They are
listed in the ASHRAE nomenclature as
R407C. In the meantime there are also further
blend varieties (e.g. R407A/R407F/
R407H) with somewhat differing compositions,
whose properties have been optimized
for particular applications (see page 18).
Unlike the substitutes for R22 in refrigeration
systems with identical blend components
(pages 18 and 19), the substitutes for
R22 in air conditioning systems and heat
pumps under consideration contain higher
proportions of R32 and R134a. A good correspondence
with the properties of R22 in
terms of pressure levels, mass flow, vapour
density and volumetric refrigerating capacity
is thus achieved. In addition, the global
warming potential is relatively low (GWP =
1774), which is a good presupposition for
favourable TEWI values.
Substitutes for R22 in air conditioning
systems and heat pumps
As the HCFC refrigerant R22 (ODP = 0.05)
is accepted only as a transitional solution, a
number of chlorine-free (ODP = 0) alternatives
have been developed and tested extensively.
They are being used for a large
range of applications.
Experience shows, however, that none of
these substitutes can replace the refrigerant
R22 in all respects. Amongst others there
are differences in the volumetric refrigerating
capacity, restrictions in possible applications,
special requirements in system
design and considerably differing pressure
levels. According to the specific operating
conditions, various alternatives may be considered.
Apart from the single-component HFC refrigerant
R134a, these are mainly blends
(different compositions) of the components
R32, R125, R134a, R143a, and R600(a).
The following description mainly concerns
the development and potential applications
of these. The halogen-free substitutes NH3,
propane and propylene as well as CO2
should also be considered, however, specific
criteria must be applied for their use
(description from page 28).
In addition, R32 and HFO/HFC blends can
also be used as alternatives (see chapter
R32 as substitute for R22, from page 23).
20
Substitutes for R22 in A/C and heat pumps
21
Fig. 21 R410A/R22 – comparison of performance data of a semi-hermetic
compressor
Fig. 22 R410A/R22 – comparison of pressure
Resulting design criteria
With regard to system technology, previous
experience with R22 can only be utilized to
a limited extent.
The distinctive temperature glide requires a
particular design of the main system components,
e.g. evaporator, condenser, expansion
valve. In this context it must be
considered that heat exchangers should
preferably be laid out for counterflow operation
and with optimized refrigerant distribution.
There are also special requirements
with regard to the adjustment of control
devices and service handling.
Furthermore, the use in systems with flooded
evaporators is not recommended as this
would result in a severe concentration shift
and layer formation in the evaporator.
BITZER can supply a widespread range
of semi-hermetic reciprocating, screw
and scroll compressors for R407C.
Converting existing R22 plants to R407C
Because of the above mentioned criteria,
no general guidelines can be defined. Each
case must be examined individually.
R410A as substitute for R22
In addition to R407C, the near-azeotropic
mixture listed by ASHRAE as R410A is
available and widely used for medium-sized
capacities in air conditioning and heat pump
applications.
An essential feature indicates nearly 50%
higher volumetric refrigerating capacity (Fig.
21) compared to R22, but with the consequence
of a proportional rise in system
pressures (Fig. 22).
At high condensing temperatures, energy
consumption/COP initially seems to be less
favourable than with R22.
This is mainly due to the thermodynamic
properties. On the other hand, very high
isentropic efficiencies are achievable (with
reciprocating and scroll compressors), so
that the real differences are lower.
Another aspect are the high heat transfer
coefficients in evaporators and condensers
determined in numerous test series, resulting
in especially favourable operating conditions.
With an optimized design, it is quite
possible for the system to achieve a better
overall efficiency than with other refrigerants.
Because of the negligible temperature glide
(< 0.2 K), the general usability is similar to
that of a pure refrigerant.
The material compatibility is comparable to
the previously discussed blends, the same
applies to the lubricants. However, the pressure
levels and the higher specific loads on
the system components need to be taken
into account.
Resulting design criteria
The fundamental criteria for HFC blends
also apply to the system technology with
R410A. However, the high pressure levels
have to be considered (43°C condensing
temperature already corresponds to 26 bar
abs.).
Compressors and other system components
designed for R22 are not suitable for this
refrigerant (or only to a limited extent).
Though, suitable compressors and system
components are available.
When considering to cover usual R22 application
ranges, the significant differences in
the thermodynamic properties (e.g. pressure
levels, mass and volume flow, vapour
density) must be taken into account. This
also requires considerable constructional
Substitutes for R22 in A/C and heat pumps
22
R427A as a substitute for R22
This refrigerant blend was introduced some
years ago under the trade name Forane®
FX100 (Arkema) and is now listed in the
ASHRAE nomenclature as R427A.
The R22 substitute is offered for the conversion
of existing R22 systems for which a
“zero ODP” solution is requested. It is an
HFC mixture with base components
R32/R125/R143a/R134a.
In spite of the blend composition based on
pure HFC refrigerants, the manufacturer
states that a simplified conversion procedure
is possible.
This is facilitated by the R143a proportion.
Accordingly, when converting from R22 to
R427A, all it takes is a replacement of the
original oil charge with ester oil. Additional
flushing sequences are not required, as
proportions of up to 15% of mineral oil
and/or alkyl benzene have no significant
effect on oil circulation in the system.
However, it must be taken into account that
the highly polarized mixture of ester oil and
HFC will lead to increased dissolving of
decomposition products and dirt in the pipework.
Therefore, generously dimensioned
suction clean-up filters must be provided.
Regarding refrigerating capacity, pressure
levels, mass flow and vapor density, R427A
is relatively close to R22. During retrofit,
essential components such as expansion
valves can remain in the system. Due to the
high proportion of blend components with
low adiabatic exponent, the discharge gas
temperature is considerably lower than with
R22, which has a positive effect at high
compression ratios.
It must be taken into account that this is
also a zeotropic blend with a distinct temperature
glide. Therefore the criteria described
for R407C apply here as well.
hydrocarbon additive. It is offered under
trade name ISCEON® MO29 (Chemours)
and listed as R422D in the ASHRAE
nomenclature.
Another refrigerant belonging to the category
of HFC/HC blends was introduced in
2009 under the trade name ISCEON®
MO99 (Chemours) – ASHRAE classification
R438A. This formulation was designed
especially for a higher critical temperature
for applications in hot climate
areas. The base components are R32,
R125, R134a, R600 and R601a.
Like R407C, all four substitute refrigerants
are zeotropic blends with a more or less
significant temperature glide. In this respect,
the criteria described for R407C
also apply here.
Apart from a similar refrigeration capacity,
there are fundamental differences in thermodynamic
properties and in oil transport
behaviour. The high proportion of R125
causes a higher mass flow with R417A/B
and R422D than with R407C, a lower discharge
gas temperature and a relatively
high superheating enthalpy. These properties
indicate that there are differences in the
optimization of system components, and a
heat exchanger between liquid and suction
lines is of advantage.
Despite the predominant proportion of HFC
refrigerants, conventional lubricants can be
used to some extent because of the good
solubility of the hydrocarbon constituent.
However, in systems with a high oil circulation
rate and/or a large volume of liquid in
the receiver, oil migration may result.
In such cases, additional measures are
necessary. For further information on oil
return and lubricants see chapter “R422A
as substitute for R22 and R502” (page 19).
Due to the high global warming potential
(GWP ≥ 2500), R417B and R422D will no
longer be allowed for new installations in
the EU from 2020. The requirements and
restrictions are specified in the F-Gas Regulation
517/2014. However, the “phasedown”
quantity limitation will also lead to
significantly restricted availability of R417A
and R438A.
BITZER compressors are suitable for use
with R417A/417B/422D/438A. An individual
selection is possible upon request.
changes to compressors, heat exchangers,
and controls, as well as measures of tuning
vibrations. There are stricter safety requirements,
e.g. affecting the quality and dimensions
of piping and flexible tube elements
(for condensing temperatures of approx.
60°C/40 bar).
Another criterion is the relatively low critical
temperature of 73°C. Irrespective of the
design of components on the high pressure
side, the condensing temperature is thus
limited.
R410A complies with the requirements of
the EU F-Gas Regulation, which will only
allow refrigerants with GWP < 2500 from
2020 onwards. However, the quantity limitation
through the “phase-down” will also
lead to significantly restricted availability.
Due to the extremely high demand for
R410A, a timely switch to alternatives is
needed in the EU.
For R410A, BITZER offers a series of
semi-hermetic reciprocating compressors
and scroll compressors.
R417A/417B/422D/438A
as substitutes for R22
Similar to the development of R422A (page
19), one aim of developing these blends
was to provide chlorine-free refrigerants
(ODP = 0) for the simple conversion of
existing R22 plants.
R417A was introduced to the market years
ago, and is also offered under the trade
name ISCEON® MO59 (Chemours). This
substitute for R22 contains the blend components
R125/R134a/R600 and therefore
differs considerably from e.g. R407C with a
correspondingly high proportion of R32.
Meanwhile, a further refrigerant based on
identical components, but with a higher
R125 content, has been offered under the
ASHRAE designation R417B. Due to its
lower R134a content, its volumetric refrigerating
capacity and pressure levels are higher
than for R417A. This results in different
performance parameters and a different
focus within the application range.
The same applies to a further blend with the
same main components, but R600a as
Substitutes for R22 in A/C and heat pumps
23
R32 as substitute for R22
As described earlier, R32 belongs to the
HFC refrigerants, but initially it was mainly
used as a component of refrigerant blends
only. An essential barrier for the application
as a pure substance so far is the flammability.
This requires adequate charge limitations
and/or additional safety measures,
especially with installations inside buildings.
In addition there are very high pressure
levels and discharge gas temperatures
(compression exponent higher than with
R22 and R410A).
On the other hand, R32 has favorable thermodynamic
properties, e.g. very high evaporating
enthalpy and volumetric refrigerating
capacity, low vapor density (low
pressure drop in pipelines), low mass flow,
and favorable power input for compression.
The global warming potential is relatively
low (GWP = 675).
Looking at these favorable properties and
taking into account the additional effort for
emission reductions, R32 will increasingly
be used as a refrigerant in factory produced
systems (A/C units and heat pumps) with
low refrigerant charges.
It was proven in flammability tests that the
necessary ignition energy is very high and
Fig. 23 R32/R410A – comparison of performance and operating data
of a scroll compressor
the flame speed is low. Therefore, R32
(like R1234yf and R1234ze) has been
placed in the new safety group A2L according
to ISO 817.
The resulting safety requirements are specified
in the revised EN 378 (amended version
2016).
R32 is also considered an alternative for
systems with larger refrigerant charge, e.g.
liquid chillers for air conditioning and process
applications and heat pumps previously
operated with R410A. However,
depending on the installation site of the
system, appropriate refrigerant charge
limits must be observed. On the other
hand, there are no such restrictions when
installed outdoors (without access to unauthorized
persons) and in machine rooms
(for example, according to EN 378-3:
2016). It should be noted, however, that
R32 precharged chillers may be subject to
special conditions during transport (according
to the Pressure Equipment Directive,
R32 is classified under Fluid Group 1).
BITZER scroll compressors of the ORBIT
GSD6 and GSD8 series have been
approved and released for use with R32.
Depending on the product group, a
special compressor version may be
required.
R427A meets the requirement of the EU
F-Gas Regulation, which will only allow
refrigerants with GWP < 2500 from 2020.
However, the quantity limitation due to the
“phase-down” will also lead to significantly
restricted availability.
BITZER compressors are suitable for
R427A. An individual selection is possible
upon demand.
Supplementary information concerning
the use of HFC blends
(see also http://www.bitzer.de)
o Technical information KT-651
“Retrofitting R22 systems to alternative
refrigerants”
Substitutes for R22 in A/C and heat pumps
24
HFOs and HFO/HFC blends
Aspects on the development of
HFO and HFO/HFC refrigerants
The decision to use the “low GWP” refrigerant
R1234yf in mobile air conditioning systems
for passenger cars (see pages 11/12)
also led to the development of alternatives
for further mobile applications as well as
stationary refrigeration, air conditioning and
heat pump systems.
Primary objectives are the use of singlecomponent
refrigerants and of mixtures
with significantly reduced GWP and similar
thermodynamic properties as the HFCs
currently used predominantly.
An essential basic component for this is
R1234yf (CF3CF=CH2). This refrigerant
belongs to the group of hydro-fluoro-olefins
(HFO), i.e. unsaturated HFCs with molecular
double bonds. This group of HFOs also
includes another substance called
R1234ze(E), which has been mainly used
as a propellant for PU foam and aerosol.
R1234ze(E) differs from R1234yf in its
molecular structure.
Both substances are the preferred choice
in terms of their properties and are also
used as basic components in HFO/HFC
blends. The Global Warming Potential is
very low − R1234yf with GWP 4 and
R1234ze(E) with GWP 7. However, these
refrigerants are flammable (safety class
A2L), meaning the refrigerant quantity in
the system must be considered in light of
the installation location. In addition, there
remain open questions concerning the
long-term stability in stationary systems
where long life cycles are common. Furthermore
the volumetric refrigerating
capacity is relatively low; for R1234yf it is
close to the level of R134a, and more than
20% lower for R1234ze(E).
There is also some uncertainty concerning
flammability. In safety data sheets,
R1234ze(E) is declared as non-flammable.
However, this only applies to its transport
and storage. When used as a refrigerant, a
higher reference temperature for flammability
tests of 60°C applies. At this temperature,
R1234ze(E) is flammable and therefore
classified in safety class A2L, like
R1234yf.
R1234ze(E) is sometimes referred to as a
R134a substitute, but its volumetric refrigerating
capacity is more than 20% lower
than that of R134a or R1234yf. The boiling
point (-19°C) also greatly restricts the application
at lower evaporation temperatures.
Its preferred use is therefore in liquid
chillers and high temperature applications.
For further information see chapter Refrigerants
for special applications, page 37.
The list of further potential HFO refrigerants
is relatively long. However, there are
only few substances that meet the requirements
in terms of thermodynamic properties,
flammability, toxicity, chemical stability,
compatibility with materials and lubricants.
These include e.g. the non-flammable
(safety group A1) low-pressure refrigerants
R1336mzz(Z), R1233zd(E) and R1224yd(Z).
These are primarily an option for liquid
chillers with large turbo-compressors, and
they can be used with positive displacement
compressors in high-temperature
applications. R1233zd(E) and R1224yd(Z)
belong to the group of HCFO (hydrochloro-
fluoro-olefins); they have a (very)
low ozone depletion potential (ODP). Upon
release into the atmosphere, however, the
molecule rapidly disintegrates.
On the other hand, there are currently no
candidates from the HFO family with similar
volumetric refrigerating capacity such as
R22/R407C, R404A/R507A and R410A
available for commercial use. Direct alternatives
for these refrigerants with significantly
lower GWPs must therefore be “constructed”
as a mixture of R1234yf and/or
R1234ze(E) with HFC refrigerants, possibly
also small proportions of hydrocarbons,
CO2 or other suitable molecules.
Though, due to the properties of the HFC
refrigerants suitable as blend components,
flammability and GWP are related diametrically
to one another. In other words: Blends
as alternatives to R22/R407C of GWP
< approx. 900 are flammable. This is also
true with alternatives for R404A/R507A in
blends of GWP < approx. 1300 and for
R410A in blends of GWP < approx. 2000.
The reason for this is the high GWP of
each of the required non-flammable components.
There are a few exceptions, which
are discussed in chapter Further development
projects with “Low GWP” refrigerants,
page 26.
For R134a alternatives, the situation is
more favorable. Due to the already quite
low GWP of R134a, a blend with R1234yf
and/or R1234ze(E) allows a formulation of
non-flammable refrigerants with a GWP of
approx. 600.
Thus, primarily two directions for development
are pursued:
o Non-flammable HFC alternatives
(blends) with GWP values according to
the above mentioned limits – safety
group A1. Regarding safety requirements,
these refrigerants can then be
utilized similar to currently used HFCs.
o Flammable HFC alternatives (blends)
with GWP values below the above mentioned
possible limits – according to
safety group A2L (for refrigerants of
lower flammability).
This group of refrigerants is then subject to
charge limitations according to future requirements
for A2L refrigerants.
Meanwhile, there are development projects
using refrigerant components with a much
higher volumetric refrigerating capacity and
pressure than R1234yf and R1234ze(E).
These can then be used to “formulate” mixtures
with R32 as an alternative to R410A,
which are optimised for certain properties.
See additional information in chapter Further
development projects with “Low GWP”
refrigerants, page 26.
R134a alternatives
In addition to the flammable HFO refrigerants
R1234yf and R1234ze(E) already
described, non-flammable mixtures are
now also available as R134a alternatives.
As previously mentioned, the initial situation
is most favorable for these.
They achieve GWP values of approx. 600 −
less than half of R134a (GWP = 1430). In
addition, this type of blends can have
azeotropic properties, so that they can be
used like pure refrigerants.
25
HFOs and HFO/HFC blends
For quite some time a blend has been
applied on a larger scale in real systems –
this was developed by Chemours and is
called OpteonTM XP-10. Results available
today are promising.
This is also true for an R134a alternative
designated Solstice® N-13 and offered by
Honeywell which, however, differs regarding
the blend composition.
The refrigerants are listed in the ASHRAE
nomenclature under R513A (Chemours)
and R450A (Honeywell).
The same category also includes the refrigerant
blends ARM-42 (ARKEMA) as well
as R456A (Mexichem AC5X).
All options show refrigerating capacity,
power input, and pressure levels similar to
R134a. Thus, components and system
technology can be taken over, only minor
changes like superheat adjustment of the
expansion valves are necessary.
Polyolester oils are suitable lubricants
which must meet special requirements, e.g.
for the utilization of additives.
Prospects are especially favorable for
supermarket applications in the medium
temperature range in a cascade with CO2
for low temperature, just as in liquid chillers
with higher refrigerant charges where the
use of flammable or toxic refrigerants
would require comprehensive safety measures.
A special case is the refrigerant R515B: an
azeotropic mixture of R1234ze(E) and
small amounts of R227ea. This combination,
declared by the manufacturer Honeywell
as an R134a alternative, is nonflammable
(A1) despite the very low GWP
of approx. 300.
However, as with the previously described
R1234ze(E), this can only be considered
an alternative under certain restrictions.
The volumetric refrigerating capacity is also
more than 20% lower than that of R134a or
R1234yf.
Substitutes for R404A/R507A and
R410A
Since the available HFO molecules
(R1234yf und R1234ze) show a considerably
smaller volumetric refrigerating capacity
than the above mentioned HFC refrigerants,
relatively large HFC proportions with
high volumetric refrigerating capacity must
be added for the particular alternatives.
The potential list of candidates is rather
limited, one option is R32 with its relatively
low GWP of 675.
However, one disadvantage is its flammability
(A2L), resulting also in a flammable
blend upon adding fairly large proportions
in order to increase the volumetric refrigerating
capacity while maintaining a favorable
GWP.
For a non-flammable blend, on the other
hand, a fairly large proportion of refrigerants
with high fluor content (e.g. R125)
must be added. A drawback here is the
high GWP of more than approx. 900 for
non-flammable R22/R407C alternatives
and more than approx. 1300 with options
for R404A/ R507A. Compared to R404A/
R507A, however, this means a reduction
down to a third.
The future drastic “phase-down” of F-Gases,
e.g. as part of the EU F-Gas Regulation,
already leads to a demand for R404A/
R507A substitutes with GWP values clearly
below 500. Although this is possible with
an adequate composition of the blend (high
proportions of HFO, R152a, possibly also
hydrocarbons), the disadvantage will be its
flammability (safety groups A2L or A2). In
this case, the application will have higher
safety requirements and will need an adequately
adjusted system technology.
R410A currently has no non-flammable
alternatives for commercial applications.
Either R32 (see page 23) as pure substance
or blends of R32 and HFO can be
used. Due to its high volumetric refrigerating
capacity, this requires a very high proportion
of R32, which is why only GWP values
from approx. 400 to 500 can be achieved.
With a higher HFO proportion, the GWP
can be reduced even further, but at the
cost of a clearly reduced refrigerating capacity.
All blend options described above with
R1234yf and R1234ze(E) show a more or
less distinct temperature glide due to boiling
point differences of the individual components.
The same criteria apply as described
in context with R407C.
Beyond that, the discharge gas temperature
of most R404A/R507A alternatives is
considerably higher than for these HFC
blends.
In single stage low temperature systems
this may lead to restrictions in the compressor
application range or require special
measures for additional cooling. In transport
applications or in low temperature
systems with smaller condensing units, the
compressors used can often not meet the
required operating ranges, due to the high
discharge gas temperatures. This is why
refrigerant blends based on R32 and HFO
with a higher proportion of R125 have also
been developed. The GWP is slightly
above 2000, but below the limit of 2500 set
in the EU F-Gas Regulation from 2020. The
main advantage of such blends is their
moderate discharge gas temperature,
which allows the operation within the typical
application limits of R404A.
Tab 4 shows the potential blend components
for the alternatives described above.
With some refrigerants the mixture components
for R22/R407C and R404A/R507A
substitutes are identical, but their distribution
in percent is different.
In the meantime, Chemours, Honeywell,
Arkema, Mexichem and Daikin Chemical
have offered corresponding chemical variants
for laboratory and field tests, and in
some cases already for commercial use. A
number of refrigerants are still declared as
being under development and are only
made available for testing purposes under
26
special agreements. Until now, trade
names are often used although a larger
number of HFO/HFC blends are already
listed in the ASHRAE nomenclature.
Tab. 5 lists a range of currently available
refrigerants or refrigerants declared as
development products. Due to the large
number of different versions and the potential
changes in development products,
BITZER has so far tested only some of the
new refrigerants. This is why in the tables
on pages 41/42 (Tab. 6/7) for the time
being only refrigerant properties of nonflammable
alternatives for R134a and
R404A/R507A (GWP < 1500) are listed
which have already received an ASHRAE
number and are commercially available.
For testing the “Low GWP” refrigerants,
AHRI (USA) has initiated the “Alternative
Refrigerants Evaluation Program (AREP)”.
It was established to investigate and evaluate
a series of the products including halogen-
free refrigerants. Some of these are
also listed in Tab 5.
Further development projects with “Low
GWP” refrigerants
For specific applications, Chemours has
developed a non-flammable (A1) R410A
alternative, which is marketed in selected
countries and regions under the trade
name OpteonTM XP41 – listed by ASHRAE
as R463A.
It is a mixture of R32, R125, R1234yf,
R134a and CO2 with a GWP of 1494.
Despite the high proportion of R32 and
R1234yf, flammability is suppressed by
mixing with R125, R134a and CO2.
Regarding thermodynamics, the differences
to R410A are comparatively small. The
addition of CO2, however, leads to a
distinct temperature glide, which may
cause certain limitations for the application
and places particular demand on the
design of the heat exchangers.
All mixture components and their properties
are well known, which means there are no
additional particularities regarding material
compatibility in comparison to the already
known R410A alternatives.
The supply of compressors for laboratory
or field tests requires an individual review
of the specific application and a special
agreement.
In the meantime, Honeywell has unveiled
the new development of a non-flammable
(A1) R410A alternative under the trade
name Solstice® N-41 – listed by ASHRAE
as R466A.
R466A is a mixture of R32, R125 and
R13I1 (CF3I − trifluoroiodomethane), an
iodine-methane derivative not previously
used in refrigeration. CF3I is not flammable,
as is R125, which means that the
refrigerant is not flammable (A1), even with
the relatively high proportion of R32 (A2L).
Despite the noticeable proportion of R125
with a GWP of 3500 (AR4), the total GWP
is 733 (AR4) and therefore in the range of
R32, R447B and R452B, which are classified
as A2L.
From a thermodynamic point of view, the
differences between R410A and R466A are
relatively small. Volumetric refrigerating
capacity, pressure levels and discharge
temperature are slightly higher, the refrigerant
mass flow deviates slightly more
(about 15 to 20% higher). The temperature
glide is also very low.
Hence, R466A appears to be a promising
substitute for R410A. However, due to the
CF3I share, there are still uncertainties
regarding long-term chemical stability and
material compatibility under the special
requirements of the refrigeration cycle.
Further investigation is required, so a final
assessment of R466A is currently not possible.
In any case, as matters stand, this
refrigerant cannot be used in state-of-theart
systems (retrofit). The supply of compressors
for laboratory tests requires an
individual review of the specific application
as well as a special agreement.
AGC Chemicals propagates R1123
(CF2=CHF) mixed with R32, partially with
addition of R134yf, as an alternative to
R410A and pure R32. It is an HCFO with
very low ozone depletion potential (ODP).
R1123 has a significantly higher volumetric
refrigeration capacity than R1234yf or
R1234ze(E) and is advantageous in this
respect. However, the pressure level is
even higher than of R32 and the critical
temperature is only about 59°C. Apart from
that, there are unanswered questions about
the chemical long-term stability under the
special requirements of the refrigeration
cycle. According to the safety data sheet,
this substance is also subject to very stringent
safety requirements.
A final assessment of these mixtures is
therefore currently not possible.
Comment from a compressor manufacturer’s
point of view:
It should be an aim to limit the product
variety currently becoming apparent and to
reduce the future supply to a few “standard
refrigerants”. It will not be possible for
component and equipment manufacturers
nor for installers and service companies to
deal in practice with a larger range of
alternatives.
BITZER was involved early on in various
projects with HFO/HFC blends and was
thus able to gain important insight into
the use of these refrigerants. Semi-hermetic
reciprocating compressors of the
ECOLINE series as well as CS. and HS.
screw compressors can already be used
with this new generation of refrigerants.
Several of them have already been
qualified and approved, the respective
performance data is available on the
BITZER SOFTWARE.
Scroll compressors of the ORBIT GSD6
and GSD8 series are approved and released
for the use of the R32/HFO mixtures
R452B and R454B. Depending on the
product group, a special compressor
version may be required.
Further information on the application
of HFOs and HFO/HFC blends see brochure
A-510, section 6 and brochure
No. 378 20 387.
HFOs and HFO/HFC blends
27
HFOs and HFO/HFC blends
Current
“
Low GWP” Alternatives for HFC refrigerant
HFC-Refrigerants
ASHRAE Trade Composition GWP③ Safety Boiling tempe- Temperature
Number Name (with blends) AR4 (AR5) group rature [°C]④ glide [K]⑤
R450A Solstice® N-13 Honeywell R1234ze(E)/134a 604 (547) A1 -24 0.6
R456A AC5X⑥ Mexichem R32/1234ze(E)/134a 687 (627) A1 -30 4.8
R513A
OpteonTM XP10 Chemours
R1234yf/134a 631 (573) A1 -30 0
R513A⑧ Daikin Chemical
R515B② – Honeywell R1234ze(E)/227ea 293 (299) A1 -19 0
R1234yf various _ 4 (< 1) A2L -30 0
R1234ze(E)② various _ 7 (< 1) A2L -19 0
R444A AC5⑥ Mexichem R32/152a/1234ze(E) 92 (89) A2L -34 10
R516A ARM-42⑦ Arkema R1234yf/R152a/R134a 142 (131) A2L -29 0
R448A Solstice® N-40 Honeywell R32/125/1234yf/1234ze(E)/134a 1387 (1273) A1 -46 6.2
R449A
OpteonTM XP40 Chemours
R32/125/1234yf/134a 1397 (1282) A1 -46 5.7
Forane® 449 Arkema
R460B LTR4X⑥ Mexichem R32/125/1234ze(E)/134a 1352 (1242) A1 -45 8.2
R452A OpteonTM XP44 Chemours R32/125/1234yf 2140 (1945) A1 -47 3.8
R452C R452C⑦ Arkema R32/125/1234yf 2220 (2019) A1 -48 3.4
R460A LTR10⑥ Mexichem R32/125/1234ze(E)/134a 2103 (1911) A1 -45 7.4
R454A
OpteonTM XL40 Chemours
R32/1234yf 239 (238) A2L -48 5.7
R454A⑧ Daikin Chemical
– ARM-20b⑦ Arkema R32/1234yf/152a 251 (251) A2L -47 6.1
R454C② OpteonTM XL20 Chemours R32/1234yf 148 (146) A2L -46 7.8
R455A Solstice® L-40X Honeywell R32/1234yf/CO2 148 (146) A2L -52 12.8
R457A② ARM-20a⑦ Arkema R32/1234yf/152a 139 (139) A2L -43 7.2
R459B② LTR1⑥ Mexichem R32/1234yf/1234ze(E) 144 (143) A2L -44 7.9
R465A ARM-25⑦⑨ Arkema R32/1234yf/290 145 (143) A2 -52 11.8
R449C OpteonTM XP20 Chemours R32/125/1234yf/134a 1251 (1146) A1 -44 6.1
R32 various – 675 (677) A2L -52 0
R452B
OpteonTM XL55 Chemours
R32/125/1234yf 698 (676) A2L -51 0.9
Solstice® L-41y Honeywell
R454B OpteonTM XL41 Chemours R32/1234yf 466 (467) A2L -51 1.0
R459A ARM-71a⑦ Arkema R32/1234yf/1234ze(E) 460 (461) A2L -50 1.7
R463A OpteonTM XP41⑩ Chemours R32/125/1234yf/134a/CO2 1494 (1377) A1 -59 12.2
R466A Solstice® N-41⑧⑩ Honeywell R32/125/13I1(CF3I) 733 (696) A1 -52 0.7
Current Alternatives Components / Mixture components “Low GWP” alternatives
HFC-Refrigerants
Safety GWP④ R1234yf R1234ze(E) R32 R152a R134a R125 R13I1⑤ CO2
② R290②
Group A2L A2L A2L A2 A1 A1 A1 A1 A3
GWP 4 7 675 124 1430 3500 <1 1 3
A1 ~ 600 _ _ _ _
R134a
A2L < 150 _ _ _ _ _
GWP 1430
A2L < 10 _ _
A1 < 2500① _ _ _
A1 ~ 1400 _ _ _ _ _
R404A/R507A
A2L < 250 _ _ _
GWP 3922/3985
A2L③ < 150 _ _ _
A2 < 150 _ _ _
A1 900..1400 _ _ _ _ _
R22/R407C A2L < 250 _ _ _
GWP 1810/1774 A2L < 150 _ _
A2 < 150 _ _ _
A1 < 1500 _ _ _ _ _
R410A A1 < 750 _ _ _
GWP 2088 A2L < 750 _
A2L ~ 400..750 _ _ _ _
Tab. 5
“
Low GWP” alternatives for HFC refrigerants
① The relatively low GWP allows the use of R134a also on longer term.
② Lower volumetric refrigerating capacity than reference refrigerant
③ AR4: according to IPCC IV // AR5: according to IPCC V – time horizon 100 years
④ Rounded values
⑤ Total glide from bubble to dew line at 1 bar (abs.)
⑥ Development product
⑦ Available 2018 .. 2020
⑧ Marketing presumably in 2019
⑨ Preferably for commercial appliances
⑩ See information under chapter Further development
projects with „Low GWP“ refrigerants.
?
?
Tab. 4 Potential mixture components for “Low GWP” alternatives (examples)
09.18
09.18
① Refrigerating capacity, mass flow, discharge gas temperature similar to R404A
② Only low percentage – due to temperature glide (CO2) and flammability (R290)
③ R32/HFO blends show lower refrigerating capacity than reference refrigerant, the addtion of CO2 leads to high temperature glide
④ Approx. values according to IPCC IV (AR4)
⑤ R13I1 (CF3I − tri-fluoroiodomethane) is an iodine-methane derivative
R134a
GWP 1430①
R22/R407C
GWP 1810/1774
R410A
GWP 2088
R404A/R507A
GWP 3922/3985
(R22/R407)
28
NH3 (Ammonia) as
alternative refrigerant
The refrigerant NH3 has been used for more
than a century in industrial and larger refrigeration
plants. It has no ozone depletion potential
and no direct global warming potential.
The efficiency is at least as good as that
of R22, in some areas even more favourable;
the contribution to the indirect global
warming effect is therefore small. In addition,
its price is exceptionally low. Is it therefore
an ideal refrigerant and an optimum substitute
for R22 or an alternative for HFCs!?
NH3 has indeed very positive features,
which can be exploited quite well in large
refrigeration plants.
Unfortunately there are also negative aspects,
which restrict the wider use in the commercial
area or require costly and sometimes
new technical developments.
A disadvantage with NH3 is the high isentropic
exponent (NH3 = 1.31 / R22 = 1.19 /
R134a = 1.1), which results in a discharge
temperature even significantly higher than
that of R22. Single stage compression is
therefore already subject to certain restrictions
below an evaporating temperature of
around -10°C.
The question of suitable lubricants is also
not satisfactorily solved for smaller plants in
some kinds of applications. The most commonly
used mineral oils and polyalpha-olefins
are not soluble with the refrigerant. They
must be separated with complex technology
and seriously limit the use of “direct expansion
evaporators” due to the deterioration in
the heat transfer.
Special demands are made on the thermal
stability of the lubricants due to the high
discharge gas temperatures. This is especially
valid when automatic operation is considered
where the oil is supposed to remain
in the circuit for years without losing any of
its stability.
NH3 has an extraordinarily high enthalpy difference
and thus a very small circulating
mass flow (approximately 13 to 15% compared
to R22). This feature, which is favourable
for large plants, makes the control of
the refrigerant injection more difficult with
small capacities.
A further criteria to be considered is the corrosive
action on copper containing materials;
pipe lines must therefore be made of steel.
The development of motor windings resistant
to NH3 is hindered, too. Another difficulty
arises from the electrical conductivity of the
refrigerant with higher moisture content.
Additional characteristics include toxicity and
flammability, which require special safety
measures for the construction and operation
of such plants.
Resulting design and
construction criteria
Based on the present “state of technology”,
industrial NH3 systems demand a completely
different plant technology, compared to
usual commercial systems.
Due to the insolubility with the lubricating oil
and the specific characteristics of the refrigerant,
high efficiency oil separators and
flooded evaporators with gravity or pump
circulation are usually employed. Because
of the danger to the public and to the product
to be cooled, the evaporator often cannot
be installed directly at the cold space
and the heat must be transported by a secondary
refrigerant circuit.
Due to the unfavorable thermal behaviour,
two stage compressors or screw compressors
with generously sized oil coolers must
be used even at medium pressure ratios.
Refrigerant lines, heat exchangers and fittings
must be made of steel; larger size
pipe lines must be examined by a certified
inspector.
Depending upon the size of the plant and
the refrigerant charge, corresponding safety
measures and special machine rooms are
required.
The refrigeration compressor is usually of
“open” design, the drive motor is a separate
component.
These measures significantly increase the
expenditure for NH3 plants, especially for
medium and smaller capacities.
Efforts are therefore being made world-wide
to develop simpler systems which can also
be used in the commercial area.
A part of the research programs is dealing
with part soluble lubricants, with the aim of
improving oil circulation in the system. Simplified
methods for automatic return of nonsoluble
oils are also being examined as an
alternative.
BITZER is strongly involved in these
projects and has a large number of
operating compressors. The experiences
up to now have revealed that
systems with partly soluble oils are difficult
to manage. The moisture content
in the system has an important influence
on the chemical stability of the
circuit and the wear of the compressor.
Besides, high refrigerant solution in the
oil (wet operation, insufficient oil temperature)
leads to strong wear on the
bearings and other moving parts. This
is due to the enormous volume change
when NH3 evaporates in the lubricated
areas.
These research developments are
being continued, with focus also on
alternative solutions for non-soluble
lubricants.
Various equipment manufacturers have
developed special evaporators, allowing
significantly reduced refrigerant charge.
There is a strong trend towards so-called
“low charge” systems, i.a. with regard to
safety requirements, which are also largely
determined by the refrigerant charge.
In addition to this, there are developments
for the “sealing” of NH3 plants: compact
liquid chillers (charge below 50 kg), installed
in a closed container and partly with
an integrated water reservoir to absorb NH3
in case of a leak. This type of compact unit
can be installed in areas which were previously
reserved for plants with refrigerants
of safety group A1 due to safety requirements.
Halogen free (natural) refrigerants
29
Halogen free (natural) refrigerants
Fig. 24 Comparison of discharge gas temperatures Fig. 25 NH3/R22 – comparison of pressure levels D
An assessment of NH3 compact systems –
instead of systems using HFC refrigerants
and conventional technology – is only possible
on an individual basis, taking into
account the particular application. From a
merely technical viewpoint and presupposing
an acceptable price level, a wider range
of products will supposedly become available
in the foreseeable future.
The product range from BITZER today
includes an extensive selection of optimized
NH3 compressors for various
types of lubricants:
o Single stage open reciprocating
compressors (displacement 19 to
152 m3/h with 1450 rpm) for air conditioning,
medium temperature and
booster applications
o Open screw compressors (displacement
84 to 1015 m3/h – with parallel
operation to 4060 m3/h – with 2900
rpm) for air conditioning, medium
and low temperature cooling.
Options for low temperature cooling:
– Single stage operation
– Economiser operation
– Booster operation
R723 (NH₃/DME) as
an alternative to NH3
The previously described experiences with
the use of NH3 in commercial refrigeration
plants with direct evaporation caused further
experiments on the basis of NH3 by
adding an oil soluble refrigerant component.
Main goals were improved oil transport and
heat transmission with conventional lubricants,
along with a reduced discharge gas
temperature for the extended application
range with single stage compressors.
The result of this research project is a refrigerant
blend of NH3 (60%) and dimethyl
ether “DME” (40%), It was developed by the
Institute of Air Handling and Refrigeration
(ILK) in Dresden, Germany, and has been
applied in a series of real systems. As a
largely inorganic refrigerant it received the
designation R723 due to it its average molecular
weight of 23 kg/kmol in accordance
to the standard refrigerant nomenclature.
Conversion of existing plants
The refrigerant NH3 is not suitable for the
conversion of existing (H)CFC or HFC
plants; they must be constructed completely
new with all components.
Supplementary BITZER information
concerning the application of NH3
(see also http://www.bitzer.de)
o Technical Information KT-640
“Application of Ammonia (NH3)
as an alternative refrigerant”
30
DME was selected as an additional component
for its good solubility and high individual
stability. Its boiling point is -26°C, the
adiabatic exponent is relatively low, it is not
toxic and available in high purity. In the
abovementioned concentration NH3 and
DME form an azeotropic blend characterised
by a slightly higher pressure level than
pure NH3. The boiling point lies at -36.5°C
(NH3 -33.4°C), 26 bar (abs.) of condensing
pressure corresponds to 58.2°C (NH3
59.7°C).
The discharge gas temperature in air conditioning
and medium temperature ranges
decreases by about 10 to 25 K (Fig. 24)
and allows for an extended application
range to higher pressure ratios. Thermodynamic
calculations conclude a single-digit
percent rise in refrigerating capacity compared
to NH3. The coefficient of performance
is similar and is even more favourable at
high pressure ratios, confirmed by experiments.
Due to the lower temperature level
during compression, an improved volumetric
and isentropic efficiency can be expected,
at least with reciprocating compressors in
case of an increasing pressure ratio.
Due to the higher molecular weight of DME,
mass flow and vapour density increase by
nearly 50% compared to NH3, although this
is of little importance to commercial plants,
especially in short circuits. In conventional
industrial refrigeration plants, however, this
is a substantial criterion with regard to pressure
drops and refrigerant circulation.
These considerations again show that the
preferred application area of R723 is in
commercial applications and especially in
liquid chillers.
Material compatibility is comparable to that
of NH3. Although non-ferrous metals (e.g.
CuNi alloys, bronze, hard solders) are
potentially suitable, provided minimum
water content in the system (< 1000 ppm),
a system design similar to typical ammonia
practise is recommended.
Mineral oils or (preferred) polyalpha olefin
are suitable lubricants. As mentioned be-
R290 (Propane) as
alternative refrigerant
R290 (propane) can also be used as a substitute
refrigerant. Being an organic compound
(hydrocarbon), it has no ozone
depletion potential and a negligible direct
global warming effect. To take into consideration
however, is a certain contribution to
summer smog.
Pressure levels and refrigerating capacity
are similar to R22, and its temperature
behaviour is as favourable as with R134a.
There are no particular problems with material.
In contrast to NH3, copper materials
are also suitable, so that semi-hermetic and
hermetic compressors are possible. Common
mineral oils of HCFC systems can be
used here as a lubricant over a wide application
range. Polyol esters (POE) and polyalpha-
olefins (PAO) offer even more favorable
properties.
Refrigeration plants with R290 have been in
operation world-wide for many years, mainly
in the industrial area – it is a “proven” refrigerant.
Meanwhile R290 is also used in smaller compact
systems with low refrigerant charges
like residential air-conditioning units and
heat pumps. Furthermore, a rising trend can
be observed in its use with commercial refrigeration
systems and chillers.
Propane is offered also as a mixture with
Isobutane (R600a) or Ethan (R170), in
order to provide a similar performance to
halocarbon refrigerants. Pure Isobutane is
mostly intended as a substitute for R12 in
small systems (preferably domestic refrigerators).
The disadvantage of hydrocarbons is their
high flammability, therefore they are classified
as refrigerants of “Safety Group A3”.
Based on the refrigerant charge quantities
commonly used in commercial systems, the
system design and risk analysis must be in
accordance with explosion protection regulations.
fore, the proportion of DME leads to improved
oil solubility and a partial miscibility.
Furthermore, the relatively low liquid density
and an increased DME concentration in the
oil enhances oil circulation. PAG oils would
be fully or partly miscible with R723 for typical
applications, but are not recommended
because of the chemical stability and high
solubility in the compressor crankcase
(strong vapour development in the bearings).
Tests have shown that the heat transfer
coefficient at evaporation and high heat flux
is improved in systems with R723 and mineral
oil compared to NH3 with mineral oil.
Further characteristics are toxicity and flammability.
The DME content lowers the ignition
point in air from 15 to 6%. However, the
azeotrope is ranked in safety group B2, but
may receive a different classification in case
of a revised assessment.
Resulting layout criteria
Experiences with the NH3 compact systems
described above can be used in plant technology.
However, the component layout has
to be adjusted considering the higher mass
flow. By appropriate selection of the evaporator
and the expansion valve, a very stable
superheat control must be ensured. Due to
the improved oil solubility,
“
wet operation”
can have considerable negative results
compared to NH3 systems with non-soluble
oil.
With regard to safety regulations, the same
criteria apply to installation and operation as
for NH3 plants.
Suitable compressors are special NH3 versions
which possibly have to be adapted to
the mass flow and the continuous oil circulation.
An oil separator is usually not necessary
with reciprocating compressors.
BITZER NH3 reciprocating compressors
are suitable for R723 in principle. An
individual selection of specifically adapted
compressors is possible on demand.
Halogen free (natural) refrigerants
31
Fig. 26 R290/R1270/R22 – comparison of performance data of a
semi-hermetic compressor
Fig. 27 R290/R1270/R22 – comparison of pressure levels
Semi-hermetic compressors in so-called
“hermetically sealed” systems are in this
case subject to regulations for hazardous
zone 2 (only seldom and short term risk).
Safety demands include special devices to
protect against excess pressures and special
arrangements for the electrical system. In
addition, measures are required to ensure
hazard free ventilation to effectively prevent
a flammable gas mixture in case of refrigerant
leakage.
Design requirements are defined by standards
(e.g. EN378) and may vary in different
countries. For systems applied in the
EU, an assessment according to EC Directive
94/9/EC (ATEX) may become necessary
as well. With open compressors, this will
possibly lead to a classification in zone 1 ‒
which demands, however, electrical equipment
in special flame-proof design.
Resulting design criteria
Apart from the measures mentioned above,
propane systems require practically no special
features in the medium and low temperature
ranges compared to a usual (H)CFC
and HFC system. When sizing components,
however, the relatively low mass flow
should be considered (approximately 55 to
60% compared to R22). An advantage here
is that the refrigerant charge can be greatly
reduced. From the thermodynamic point of
view, an internal heat exchanger between
the suction and liquid line is recommended
as this will improve the refrigerating capacity
and COP.
Owing to the particularly high solubility of
R290 (and R1270) in common lubricants,
BITZER R290/R1270 compressors are
charged with special oil of a high viscosity
index and particularly good tribological
properties.
Again, an internal heat exchanger is of
advantage as it leads to higher oil temperatures,
lower solubility and therefore improved
viscosity.
Due to the very favourable temperature
behaviour (Fig. 25), single stage compressors
can be used down to approximately
– 40°C evaporation temperature. R290 could
thus also be considered as an alternative
for some of the HFC blends.
A range of ECOLINE compressors and
- compact screws is available for
R290. Due to the individual requirements
a specifically equipped compressor version
is offered. Inquiries and orders
need a clear reference to R290. The
handling of the order includes an individual
agreement between the contract partners.
Open reciprocating compressors
are also available for R290, together with
a comprehensive program of flame-proof
accessories which may be required.
Conversion of existing plants with R22
or HFC
Due to the special safety measures when
using R290, a conversion of existing systems
only seems possible in exceptional
cases. They are limited to systems, which
can be modified to meet the corresponding
safety regulations with an acceptable effort.
Supplementary BITZER information
concerning the use of R290
(see also http://www.bitzer.de)
o Technical Information KT-660
“Application of Propane and Propylene
with semi-hermetic compressors”
Halogen free (natural) refrigerants
32
ever, tests by hydrocarbon manufacturers
and stability tests in real applications show
practically no reactivity in refrigeration systems.
Doubts have occasionally been
voiced in some literature regarding possible
carcinogenic effects of propylene. These
assumptions have been disproved by appropriate
studies.
Resulting design criteria
With regard to system technology, experience
gained from the use of propane can
widely be applied to propylene. However,
component dimensions have to be altered
due to higher volumetric refrigerating capacity
(Fig. 26). The compressor displacement
is correspondingly lower, as are the suction
and high pressure volume flows. Because
of higher vapour density, the mass flow is
almost the same as for R290. As liquid density
is nearly identical, the same applies to
the liquid volume in circulation.
As with R290, an internal heat exchanger
between suction and liquid lines is of
advantage. However, due to the higher dis-
Propylene (R1270) as an
alternative to Propane
For some time there has been increasing
interest in using propylene (propene) as a
substitute for R22 or HFC. Due to its higher
volumetric refrigerating capacity and lower
boiling temperature (compared to R290),
applications in medium and low temperature
systems are of particular interest, e.g. liquid
chillers for supermarkets. On the other
hand, higher pressure levels (> 20%) and
discharge gas temperatures have to be
taken into consideration, thus restricting the
possible application range.
Material compatibility is comparable to
propane, as is the choice of lubricants.
Propylene is also easily inflammable and
belongs to the safety group A3. The same
safety regulations are therefore to be
observed as with propane (page 31).
Due to the chemical double bond, propylene
reacts quite easily, risking polymerization at
high pressure and temperature levels. Howcharge
gas temperature of R1270, restrictions
are partly necessary at high pressure ratios.
A range of ECOLINE compressors and CS.
compact screws is available for R1270.
Due to the individual requirements a
specifically equipped compressor version
is offered. Inquiries and orders need a
clear reference to R1270.
The handling of the order includes an individual
agreement between the contract
partners. Open reciprocating compressors
are also available for R1270, together with
a comprehensive program of flame-proof
accessories which may be required.
Supplementary BITZER information
concerning the use of R1270
(see also http://www.bitzer.de)
o Technical Information KT-660
“Application of Propane and Propylene
with semi-hermetic compressors”
Halogen free (natural) refrigerants
33
Fig. 28 R744(CO2) – pressure/enthalpy diagram
long periods. It should further be noted that
the heat transfer coefficients of CO2 are
considerably higher than of other refrigerants
– with the potential of very low temperature
differences in evaporators, condensers,
and gas coolers. Moreover, the
necessary pipe dimensions are very small,
and the influence of the pressure drop is
comparably low. In addition, when used as
a secondary fluid, the energy demand for
circulation pumps is extremely low.
In the following section, a few examples of
subcritical systems and resulting design criteria
are described. An additional section
provides details on transcritical applications.
Subcritical CO2 applications
From energy and pressure level points of
view, very beneficial applications can be
seen for industrial and larger commercial
refrigeration plants. For this, CO2 can be
used as a secondary fluid in a cascade system
and if required, in combination with a
further booster stage for lower evaporating
temperatures (Fig. 30).
were e.g. marine refrigeration systems. With
the introduction of the “(H)CFC Safety Refrigerants”,
CO2 became less popular and
had nearly disappeared by the 1950’s.
The main reasons for that are its relatively
unfavourable thermodynamic characteristics
for usual applications in refrigeration and air
conditioning.
The discharge pressure with CO2 is extremely
high, and the critical temperature at
31°C (74 bar) very low. Depending on the
heat sink temperature at the high pressure
side, transcritical operations with pressures
beyond 100 bar are required. Under these
conditions, energy efficiency is often lower
than in the classic vapour compression process
(with condensation), therefore the indirect
global warming effect is higher.
Nonetheless, there is a range of applications
in which CO2 can be used very economically
and with favourable eco-efficiency.
These include subcritical cascade plants,
but also transcritical systems, in which the
temperature glide on the high pressure side
can be used advantageously, or the system
conditions permit subcritical operation for
Carbon dioxide R744 (CO2)
as an alternative refrigerant
and secondary fluid
CO2 has had a long tradition in the refrigeration
technology reaching far into the 19th
century. It has no ozone depleting potential,
a negligible direct global warming potential
(GWP = 1), is chemically inactive, non-flammable
and not toxic in the classical sense.
Therefore, CO2 is not subjected to the stringent
containment demands of HFCs (F-Gas
Regulation) and flammable or toxic refrigerants.
However, compared to HFCs the
lower critical value in air has to be considered.
For closed rooms, this may require
special safety and detection systems.
CO2 is also low in cost and there is no
necessity for recovery and disposal. In addition,
it has a very high volumetric refrigerating
capacity: depending on operating conditions,
approx. 5 to 8 times as high as R22
and NH3.
Above all, the safety relevant characteristics
were an essential reason for the initial widespread
use. The main focus for applications
Halogen free (natural) refrigerants
34
The operating conditions are always subcritical
which guarantees good efficiency levels.
In the most favourable application
range (approx. -10 to -50°C), pressures are
still on a level where already available components
or items in development, e.g. for
R410A, can be matched with acceptable
effort.
Resulting design criteria
For the high temperature side of such a
cascade system, a compact cooling unit can
be used, whose evaporator serves on the
secondary side as the condenser for CO2.
Chlorine-free refrigerants are suitable, e.g.
NH3, HCs or HFCs, HFO and HFO/HFC
blends.
With NH3, the cascade heat exchanger
should be designed in a way that the dreaded
build-up of ammonium carbonate in the
case of leakage is prevented. This technology
has been applied in breweries for a
long time.
A secondary circuit for larger plants with
CO2 could be constructed utilising, to a
wide extent, the same principles for a low
pressure pump circulating system, as is
often used with NH3 plants. The essential
difference is the condensing of CO2 in the
cascade cooler, while the receiver tank
(accumulator) only serves as a supply vessel.
The extremely high volumetric refrigerating
capacity of CO2 (latent heat through the
changing of phases) leads to very low mass
flow rates, allows for small cross sectional
pipe and minimal energy needs for the circulating
pumps.
There are different solutions for the combination
with a further compression stage, e.g.
for low temperatures.
Fig. 30 shows a variation with an additional
receiver, which one or more booster compressors
will bring down to the necessary
evaporation pressure. Likewise, the discharge
gas is fed into the cascade cooler,
condenses and is carried over to the receiver
(MT). The feeding of the low pressure
receiver (LT) is achieved by a level control
device. Instead of conventional pump circulation
the booster stage can also be built as
a so-called LPR system.
The circulation pump is thus not necessary,
but the number of evaporators is then limited
with view to an even distribution of the
injected CO2.
In the case of a system breakdown where a
high rise in pressure could occur, safety
valves can vent the CO2 to the atmosphere
with the necessary precautions. As an alternative,
additional cooling units for CO2 condensation
are also used where longer shutoff
periods can be bridged without a critical
pressure increase.
For systems in commercial applications, a
direct expansion version is possible as well.
Supermarket plants with their usually widely
branched pipe work offer an especially
good potential in this regard: The medium
temperature system is carried out in a conventional
design or with a secondary circuit,
for low temperature application combined
with a CO2 cascade system (for subcritical
operation). A system example is shown in
Fig. 31.
For a general application, however, not all
requirements can be met at the moment. It
is worth considering that system technology
changes in many respects and specially adjusted
components are necessary to meet
the demands.
Fig. 31 Convention al re friger ati on system combined with CO2 l ow
tempe rature cascade
Halogen free (natural) refrigerants
35
an intermediate pressure receiver. Depending
on the temperature curve of the heat
sink, a system designed for transcritical
operation can also be operated subcritically
‒ with higher efficiency. In this case, the
gas cooler becomes the condenser.
Another feature of transcritical operation is
the necessary control of the high pressure
to a defined level. This “optimum pressure”
is determined as a function of gas cooler
outlet temperature by means of balancing
between the highest possible enthalpy difference
and at once minimum compression
work. It must be adapted to the relevant
operating conditions using an intelligent
modulating controller (see system example,
Fig. 32).
As described before, under purely thermodynamic
aspects, the transcritical operating
mode appears to be unfavourable in terms
of energy efficiency. In fact, this is true for
systems with a fairly high temperature level
of the heat sink on the high pressure side.
However, additional measures can improve
efficiency, such as the use of parallel compression
(economiser system) and/or ejectors
or expanders for recovering the throttling
losses during expansion of the
refrigerant.
Apart from that, there are application areas
in which a transcritical process is advantageous
in energy demand. These include
heat pumps for sanitary water or drying processes.
With the usually very high temperature
gradients between the discharge temperature
at the gas cooler intake and the
heat sink intake temperature, a very low
gas temperature outlet is achievable. This is
facilitated by the temperature glide curve
and the relatively high mean temperature
difference between CO2 vapour and secondary
fluid. The low gas outlet temperature
leads to a particularly high enthalpy difference,
and therefore to a high system COP.
Low-capacity sanitary water heat pumps are
already manufactured and used in large
quantities. Plants for medium to higher
capacities (e.g. hotels, swimming pools,
drying systems) must be planned and
realised individually. Their number is therefore
still limited, but with an upward trend.
Apart from these specific applications, there
is also a range of developments for the
classical areas of refrigeration and air-conditioning,
e.g. supermarket refrigeration.
Installations with parallel compounded compressors
are in operation to a larger scale.
They are predominantly booster systems
where medium and low temperature circuits
are connected (without heat exchanger).
The operating experience and the calculated
energy costs show promising results.
However, the investment costs are still
higher than for conventional plants with
HFCs and direct expansion.
On the one hand, the favourable energy
costs are due to the high degree of optimized
components and the system control,
as well as the previously described advantages
regarding heat transfer and pressure
drop. On the other hand, these installations
are preferably used in climate zones permitting
very high running times in subcritical
operation due to the annual ambient temperature
profile.
For increasing the efficiency of CO2 supermarket
systems and for using them in
warmer climate zones, the technologies
described above using parallel compression
and/or ejectors are increasingly used.
Therefore, but also because of very
demanding technology and requirements for
qualification of planners and service personnel,
CO2 technology cannot be regarded as
a general replacement for plants using HFC
refrigerants.
Resulting design criteria
Detailed information on this topic would go
beyond the scope of this publication. In any
case, the system and control techniques
are substantially different from conventional
plants. Already when considering pressure
levels as well as volume and mass flow
ratios specially developed components,
controls, and safety devices as well as suitably
dimensioned pipework must be provided.
The compressors, for example, must be
properly designed because of the high
vapour density and pressure levels (particularly
on the suction side). There are also
specific requirements with regard to materials.
Furthermore only highly dehydrated
CO2 must be used.
High demands are made on lubricants as
well. Conventional oils are mostly not miscible
and therefore require costly measures
to return the oil from the system. On the
other hand, if miscible and highly soluble
POE are used, the viscosity is strongly
reduced. Further information to lubricants
see page 40 and Fig. 37, page 44.
For subcritical CO2 applications BITZER
offers two series of special compressors.
Supplementary BITZER information concerning
compressor selection for subcritical
CO2 systems
(see also http://www.bitzer.de)
o Brochure KP-120
Semi-hermetic reciprocating compressors
for subcritical CO2 applications
(LP/HP standstill pressures up to
30/53 bar)
o Brochure KP-122
Semi-hermetic reciprocating compressors
for subcritical CO2 applications
(LP/HP standstill pressures up to
100 bar)
o Additional publications on request
Transcritical CO2 applications
Transcritical processes are characterized in
that the heat rejection on the high pressure
side proceeds isobar but not isotherm.
Contrary to the condensation process during
subcritical operation, gas cooling (desuperheating)
occurs, with corresponding
temperature glide. Therefore, the heat
exchanger is described as gas cooler. As
long as operation remains above the critical
pressure (74 bar), only high-density vapour
will be transported. Condensation only
takes place after expansion to a lower pressure
level – e.g. by interstage expansion in
Halogen free (natural) refrigerants
36
The compressor technology is particularly
demanding. The special requirements result
in a completely independent approach. For
example, this involves design, materials
(bursting resistance), displacement, crank
gear, working valves, lubrication system, as
well as compressor and motor cooling.
Hereby, the high thermal load severely limits
the application for single-stage compression.
Low temperature cooling requires
2-stage operation, whereby separate high and
low pressure compressors are particularly
advantageous with parallel compounded
systems.
The criteria mentioned above in connection
with subcritical systems apply to an even
higher degree for lubricants. For further
information to lubricants see page 40 and
Fig. 37, page 44.
Further development is necessary in various
areas, and transcritical CO2 technology
cannot in general be regarded as state-ofthe-
art.
CO2 in mobile
air-conditioning systems
Within the scope of the long-discussed
measures for reducing direct refrigerant
emissions, and the ban on the use of
R134a in MAC systems within the EU, the
development of CO2 systems has been
pursued intensively since several years.
At first glance, efficiency and therefore indirect
emissions from CO2 systems under
typical ambient conditions appear to be
unfavourable. But it must be considered
that present R134a systems are less efficient
than stationary plants of the same
capacity, because of specific installation
conditions and high pressure losses in
pipework and heat exchangers. With CO2,
pressure losses have significantly less influence.
Moreover, system efficiency is further
improved by the high heat transfer coefficients
in the heat exchangers.
This is why optimized CO2 air conditioning
systems are able to achieve efficiencies
comparable to those of R134a. Regarding
the usual leakage rates of such systems, a
more favourable balance is obtained in
terms of TEWI.
From today’s viewpoint, it is not yet possible
to make a prediction as to whether CO2 can
in the long run prevail in this application. It
certainly also depends on the experience
with “low GWP” refrigerants that have been
introduced by the automotive industry (see
chapter “Low GWP” HFO refrigerants
R1234yf and R1234ze(E), page 11). Further
aspects such as operating safety, costs,
and global logistics will play an important
role.
Fig. 32 Example of a transcritical CO2 Booster system
?? ??
??????????????????
For transcritical CO2 applications,
BITZER offers a wide range of special
compressors. Their use is aimed at specific
applications, therefore individual
examination and assessment are
required.
Suplementary BITZER information concerning
compressor selection for transcritical
CO2 systems
(see also http://www.bitzer.de)
o Brochure KP-130
Semi-hermetic reciprocating compressors
for transcritical CO2 applications
o Additional publications upon request
Simplified
sketch
Halogen free (natural) refrigerants
37
R124 and R142b
as substitutes for
R114 and R12B1
In place of R114 and R12B1 previously
used in high-temperature heat pumps and
crane air conditioning systems, HCFCs
R124 and R142b can still be used as alternatives
in most regions outside of the EU.
With these gases it is also possible to use
long proven lubricants, preferably mineral
oils and alkyl benzenes with high viscosity.
Because of their ozone depleting potential,
these refrigerants will only be an interim
solution. In the EU member states, the
application of HCFCs is no longer allowed.
For R124 and R142b the same restrictions
are valid as for R22 (page 8). The flammability
of R142b and the resulting safety
implications should also be considered
(safety group A2).
Resulting design criteria/
Converting existing plants
Compared to R114, the alternatives have
lower boiling temperatures (approx. -10°C),
which results in larger differences in the
pressure levels and volumetric refrigerating
capacities. This leads to stronger limitations
in the application range at high evaporating
and condensing temperatures.
Converting an existing installation will in
most cases necessitate the exchange of the
compressor and control devices. Owing to
the lower volume flow (higher volumetric
refrigerating capacity), adjustments to the
evaporator and the suction line may be
required.
Over the previous years BITZER compressors
have been found to be well
suited with R124 and R142b in actual
installations. Depending on the application
range and compressor type modifications
are necessary, however. Performance
data including further design
instructions are available on request.
Chlorine free substitutes for
special applications
Due to the limited market for systems with
extra high and low temperature applications,
the development of alternative refrigerants
and system components for these has
been pursued less intensely.
In the meantime, a group of alternatives for
the CFC R114 and Halon R12B1 (high temperature),
R13B1, R13 and R503 (extra low
temperature) have been offered as replacements.
On closer examination, however, the
thermodynamic properties of the alternatives
differ considerably from the previously
used substances. This can cause costly
changes especially with the conversion of
existing systems.
Alternatives for R114
and R12B1
R227ea and R236fa are considered suitable
substitutes even though they may no longer
be used in new installations in the EU from
2020, due to their high GWP.
R227ea cannot be seen as a full replacement.
Although tests and experience in real
plants show favorable results, a critical temperature
of 102°C limits the condensing
temperature to 85..90°C with conventional
plant technology.
R236fa provides the more favourable conditions
at least in this regard – the critical
temperature is above 120°C. A disadvantage,
however, is the lower volumetric refrigerating
capacity. It is similar to R114 and
40% below the performance of R124, which
is widely used for extra high temperature
applications today.
R600a (Isobutane) will be an interesting
alternative where safety regulations allow
the use of hydrocarbons (safety group A3).
With a critical temperature of 135°C, condensing
temperatures of 100°C and more
are within reach. The volumetric refrigerating
capacity is almost identical to R124.
The “Low GWP” refrigerant R1234ze(E) can
also be regarded as a potential candidate
for extra high temperature applications
(page 24). Compared to R124, its refrigerating
capacity is 10 to 20% higher, its pressure
level about 25% higher. At identical
refrigerating capacities, the mass flow differs
only slightly. Its critical temperature is
107°C, which would enable an economical
operation up to a condensing temperature
of about 90°C. Though, like R1234yf,
R1234ze(E) has low flammability and therefore
classified into the new safety group
A2L. The corresponding safety regulations
must be observed.
As no sufficient operating experience is
available so far, the suitability of this refrigerant
for long-term use cannot be assessed
yet.
For high temperature heat pumps in process
technology and special applications at
high temperatures, Chemours has presented
an HFO-based refrigerant called OpteonTM
MZ (R1336mzz(Z)). Its critical temperature
is 171°C, the boiling temperature
33.1°C. This enables an operation at condensing
temperatures far above 100°C for
which only purpose-built compressors and
system components can be used.
R1336mzz(Z) has a GWP < 10 but is not
flammable according to tests. This means a
classification in safety group A1.
A more detailed evaluation is not yet possible
with respect to the chemical stability of
the refrigerant and of the lubricants at the
very high temperatures and the usually very
long operating cycles of such systems. The
special applications also include cogeneration
systems – the so-called “Organic
Rankine Cycle” (ORC) – which become
increasingly important. In addition to
R1336mzz(Z) as a potentially suitable operating
fluid, a series of other substances
are also possible, depending on the temperature
level of the heat source and the
heat sink.
Refrigerants for special applications
38
Fig. 33 R13B1/HFC alternatives – comparison of discharge gas temperatures
of a 2-stage compressor
in their construction accordingly. For
several years BITZER has been involved
in various projects and has already
gained important knowledge with this
technology and experience in design and
application.
A comprehensive description of ORC
systems would go beyond the scope of
this Refrigerant Report. Further information
is available upon request.
Alternatives for R13B1
Besides R410A, ISCEON® MO89 (DuPont)
can be regarded as potential R13B1 substitute.
For R410A, a substantially higher discharge
gas temperature than for R13B1 is
to be considered, which restricts the application
range even in 2-stage compression
systems to a greater extent.
ISCEON® MO89 has been used for many
years, preferably in freeze-drying plants.
Meanwhile, production has ceased. However,
for historical reasons the refrigerant will
continue to be included in this Report. It is a
mixture of R125 and R218 with a small proportion
of R290. Due to the properties of
the two main components, density and
They include R245fa (GWP = 1050) having
a critical temperature of 154°C, which like
R1336mzz(Z) is also suitable as refrigerant
for chillers with large centrifugal compressors.
Solvay offers further refrigerants for ORC
applications, containing the base component
R365mfc. A product with the trade
name Solkatherm® SES36 already presented
several years ago contains perfluoropolyether
as a blend component. It is an
azeotropic blend with a critical temperature
of 178°C. Meanwhile two zeotropic blends
containing R365mfc and R227ea have been
developed whose critical temperatures are
177°C and 182°C, due to different mixing
ratios. They are available under the trade
names Solkatherm® SES24 and SES30.
In ORC systems zeotropic behavior may be
advantageous. In the case of single-phase
heat sources and heat sinks, the temperature
difference at the so-called “pitch point”
can be raised by the gliding evaporation
and condensation. This leads to improved
heat transmission due to the higher driving
average temperature difference.
As an expander for ORC systems screw
and scroll compressors can be adapted
mass flow are relatively high, and discharge
gas temperature is very low. Liquid
subcooling is of particular advantage.
Both of the mentioned refrigerants have
fairly high pressure levels and are therefore
limited to 40..45°C condensing temperature
with the usually applied 2-stage compressors.
They also show less capacity
than R13B1 at evaporating temperatures
below -60°C.
In addition to this, the steep fall of pressure
limits the application at very low temperatures
and may require a change to a cascade
system with e.g. R23, R508A/B or
R170 (ethane) in the low temperature
stage.
Lubrication and material compatibility are
similar to other HFC blends.
The EU F-Gas Regulation (Annex III) provides
an exemption “for applications
designed to cool products below -50°C”.
This means that even after 2020, refrigerants
with GWP > 2500 can be used in new
plants. Due to the “phase-down” however,
quantities will be limited, resulting in a considerable
increase in price and very limited
availability.
It is therefore imperative to develop alternative
solutions for which, however, no
overall recommendation is possible. Twostage
compressors may be operated e.g.
with R448A/449A (safety group A1) or
R1270 (A3) down to an evaporation temperature
of -60..- 65°C. Although R404A/
R507A alternatives with GWP < approx.
250 (safety group A2L) are potentially possible,
so far only limited experience has
been gained even for typical low temperature
refrigeration.
At evaporating temperatures of down to
-50..-52°C, operation with CO2 is also
possible − either in a two-stage or a cascade
system.
However, each variant generally requires a
specific design and laboratory tests.
Refrigerants for special applications
39
Refrigerants for special applications
Alternatives for R13
and R503
For these substances, the situation is still
quite favorable from a purely technical
point of view; they can be replaced by R23
and R508A/R508B. R170 (ethane) is also
suitable if the safety regulations allow a
flammable substance (safety group A3).
Due to the partly steeper pressure curve of
the alternative refrigerants and the higher
discharge gas temperature of R23 compared
to R13, differences in performance
and application ranges for the compressors
must be considered. Heat exchangers and
controls have to be adapted individually.
As lubricants for R23 and R508A/B, polyol
ester oils are suitable, but must be
matched for the special requirements at
extreme low temperatures.
R170 is also well soluble with conventional
oils, but an adaptation to the temperature
will be necessary.
Applications with these refrigerants are
purely for cooling products below -50°C.
Hence, the exemption described in the previous
chapter in the EU F-Gas Regulation
applies in particular.
For R23 and R508A/B, however, the
effects of “phase-down” are particularly
serious. The GWP values range from
13200 to 14800 (AR4). Even relatively
small quantities are therefore very much at
the expense of the available quotas.
Apart from R170 (ethane) with the special
safety precautions required for A3 refrigerants,
there are no directly comparable
alternatives for R23 and R508A/B within
the group of HFOs or HFO/HFC mixtures
(safety groups A1 or A2L). In many cases,
however, the use of A3 refrigerants is not
possible or would involve unjustifiable
expenses and high costs in the relevant
special applications.
Following these challenges, research projects
have been initiated, in which the use
of N2O (nitrous oxide) and mixtures of N2O
and CO2 are examined in more detail.
Extensive examinations and tests at the
Karlsruhe University of Applied Sciences
and the Institute of Air Handling and Refrigeration
(ILK) in Dresden show revealing
results.
N2O (R744A) has similar thermodynamic
properties and pressures as CO2, identical
molecular weight, a very low triple point
(-90.8°C) and a critical temperature of
36.4°C. The GWP is 298, which is a fraction
of the R23 and R508A/B values. In
sum, an ideal alternative for special applications
up to about -80°C evaporating temperature?
At first glance, these are very positive features.
Unfortunately, there are also negative
aspects that virtually preclude the use
of N2O as a pure substance.
Pure N2O as a refrigerant is a safety risk: It
has a narcotic effect and promotes fire.
N2O can oxidize other substances. In addition,
under specific conditions (pressure,
temperature or ignition source), exothermic
decomposition reactions can occur, which
fundamentally call into question the permanently
safe operation of a refrigeration
system with pure N2O.
By adding CO2 in higher percentages (over
approx. 15%), the triple point is slightly
shifted towards higher temperatures, but at
the same time a positive effect (“phlegmatization”)
on oxidation and chemical decomposition
is achieved. The safety risk is
reduced significantly, and material compatibility
is considerably improved. Nevertheless,
there are special challenges i.a. for
lubricants with a high resistance to oxidation
which must also be suitable for the
special requirements at low temperature
conditions.
Investigations are ongoing. A final assessment
is not yet possible, which is why no
guidelines can currently be drawn up for
the design and implementation of such
systems.
BITZER has carried out investigations
and also collected experiences with
several of the substitutes mentioned.
Performance data and instructions are
available on request. Due to the individual
system technology for these special
installations, consultation with
BITZER is necessary.
40
Lubricants
Lubricants for compressors
Positive displacement compressors ‒ as
are predominantly used in commercial and
industrial refrigeration, air conditioning and
heat pump systems ‒ are commonly oillubricated.
Despite appropriate constructional
measures and/or installation of an oil
separator, a small amount of oil is pumped
into the circuit together with the compressed
gas flow. To stabilise the oil balance,
suitable measures for continuous oil return
must be taken. Oils that are soluble and
miscible with the refrigerant are advantageous.
The refrigerant dissolved in the oil significantly
reduces the viscosity, improving
oil fluidity and minimising the negative
influence on heat transfer in heat exchangers.
In the past, so-called naphthenic mineral
oils and synthetic alkylbenzenes were preferred.
For systems with CFC and HCFC
refrigerants (for example R22) and hydrocarbons,
they are very favorable with
regard to solubility and miscibility. On the
other hand, owing to their low polarity, they
are insufficiently miscible with the highly
polar HFC and HFO refrigerants and are
therefore not properly and sufficiently
drawn into the refrigeration cycle.
Immiscible oils can accumulate in the heat
exchangers and hinder the heat transfer so
much that operation of the system is no
longer possible.
Therefore, new lubricants with appropriate
solubility/miscibility have been developed
for systems with HFC and HFO refrigerants.
These are oils based on polyol ester
(POE) and polyalkylene glycol (PAG).
They have similar or better lubricating properties
than previously customary oils, but
are more or less hygroscopic, depending
on the refrigerant solubility. This requires
special care in manufacturing (including
drying), transport, storage and charging, so
that chemical reactions in the plant – such
as hydrolysis in POE – are avoided.
PAG-based oils are particularly critical concerning
water absorption. In addition, they
have a relatively low dielectric strength and
are therefore less suitable for semi-hermetic
and hermetic compressors. They are
primarily used in mobile air conditioning
systems with open drive compressors,
where special requirements for lubrication
and best solubility/miscibility are required
because of a high oil circulation rate. To
avoid copper plating, non-ferrous metals
are used in these systems.
The remaining refrigeration industry so far
prefers POE oils. The extensive experience
gained with them is positive if the water
content in the oil does not significantly
exceed 100 ppm. However, only oils specified
by the compressor manufacturer may
be used. Because of the increased reactivity
of HFOs with oil, this is especially true
for systems with these refrigerants.
Compressors for factory-made air conditioners
and chillers are also increasingly
being charged with polyvinyl ether (PVE)
oils. Although they are more hygroscopic
than POE, they are very resistant to hydrolysis,
thermally and chemically stable, have
good lubricating properties and high dielectric
strength. In contrast to POE, they are
less prone to the formation of metal soaps
and thus offer more security against blokkage
of capillaries.
Special requirements for the lubricants
exist with CO2 systems. Specially formulated
POEs are also suitable for use in widely
ramified pipe networks due to their particularly
good solubility/miscibility. However,
these properties have a negative effect on
viscosity and lubricity (tribology) and therefore
require compressors with an extremely
robust and wear-resistant drive gear. At
very high loads, e.g. heat pumps, PAG oils
specially developed for CO2 applications
ensure even more favorable lubrication
conditions.
Due to the thermodynamic properties of
ammonia (NH3) and the resulting plant
engineering, non-soluble/miscible oils are
advantageous. These include for example
mineral oils and polyalphaolefins (PAO).
However, they require a special technique
for oil separation and oil recirculation. For
further explanation as well as additional
information on applications when using partially
soluble PAG oils see chapter NH3
(Ammonia) as alternative refrigerant (page
28) and supplementary information (see
below).
Further information see Fig. 37 “Overview
lubricants”, page 44 and explanations for
the particular refrigerants.
Supplementary BITZER information concerning
lubricants
(see also http://www.bitzer.de)
o Technical Information KT-500
„Refrigeration oil for reciprocating
compressors with (H)CFC or NH3”
o Technical Information KT-510
„Polyolester oils BSE32 and BSE55 for
BITZER reciprocating compressors“
o Technical Information KT-640
„Application of Ammonia (NH3) as an
alternative refrigerant” – chapter:
“Lubricants and their influence on the
system design”
o Technical Information KT-660
„Use of propane (R290) and propene
(R1270) in semi-hermetic BITZER
compressors” – chapter: “Lubricants”
o Operating Instructions KB-120 and
KB-130
„Semi-hermetic reciprocating compressors
for CO2 applications“
o Manuals for screw compressors
SH-100 to SH-500 – chapter: „Lubricants”
Further information see Fig. 37 Lubricants
for compressors, page 44 and explanations
for the particular refrigerants.
AR4: according to IPCC IV – time horizon 100 years –
also basis for EU F-Gas Regulation 517/2014
AR5: according to IPCC V – time horizon 100 years
N/A Data not yet published.
Alternative refrigerant has larger deviation in
refrigerating capacity and pressure
Alternative refrigerant has larger deviation
below -60°C evaporating temperature
Also used as a component in R290/
600a-Blends (direct alternative to R12)
Classification according to EN 378-1
and ASHRAE 34
According to EN 378:2016
09.16
3
4
5
1 6
2
These data are valid subject to reservations; they are based on information published by various refrigerant manufacturers.
Tab. 6 Refrigerant properties (continued on Tab. 7)
41
Refrigerant properties
R22
R124
R142b
R134a
R152a
R125
R143a
R32
R227ea
R236fa
R23
R404A
R507A
R407A
R407F
R407H
R422A
R437A
R407C
R417A
R417B
R422D
R427A
R438A
R410A
R508A
R508B
R1234yf
R1234ze(E)
R513A (XP10)
R450A (N-13)
R448A (N-40)
R449A (XP40)
R717
R723
R600a
R290
R1270
R170
R744
CHClF2
CHClFCF3
CCIF2CH3
CF3CH2F
CHF2CH3
CF3CHF2
CF3CH3
CH2F2
CF3-CHF-CF3
CF3-CH2-CF3
CHF3
R143a/125/134a
R143a/125
R32/125/134a
R32/125/134a
R32/125/134A
R125/134a/600a
R125/134a/600/601
R32/125/134a
R125/134a/600
R125/134a/600
R125/134a/600a
R32/125/143a/134a
R32/125/134a/600/601a
R32/125
R23/116
R23/116
CF3CF=CH2
CF3CH=CHF
R1234yf/134a
R1234ze(E)/134a
R32/125/1234yf/1234ze(E)/134a
R32/125/1234yf/134a
NH3
NH3/R-E170
C4H10
C3H8
C3H6
C2H6
CO2
R502 (R12 )
R114 , R12B1
R12 (R500)
R13 (R503)
R503
R134a
R404A, R507A
R22 (R13B1 )
R22
R22 (R502)
R404A (R22)
R404A (R22)
R134a
R404A (R22)
R404A (R22)
R23
Diverse
R12B1, R114
R114
R12 (R22 )
mainly used as
part components
for blends
R410A (R22)
HFC Single-component Refrigerants
Valid for single stage compressors
Data on request (operating conditions
must be given)
Triple point at 5.27 bar
Stated performance data are average values
based on calorimeter tests.
Rounded values
Total glide from bubble to dew line –
based on 1 bar (abs.) pressure.
Real glide dependent on operating
conditions.
Approx. values in evaporator:
H/M 70%; L 60% of total glide
Reference refrigerant for these values
is stated in Tab. 6 under the nomination
“Substitute for” (column 3)
Letter within brackets indicates
operating conditions
H High temp (+5/50°C)
M Medium temp (-10/45°C)
L Low temp (-35/40°C)
42
Tab. 7 Refrigerant properties
3 4
5
6
1
2
Refrigerant properties
R2 2
R1 24
R1 42b
R134a
R152a
R125
R143a
R32
R227ea
R236fa
R23
R404A
R507A
R407A
R407F
R407H
R422A
R437A
R407C
R417A
R417B
R422D
R427A
R438A
R410A
R508A
R508B
R1234yf
R1234ze(E)
R513A (XP1 0)
R450A (N-13)
R448A (N-40)
R449A (X P4 0)
R717
R723
R600a
R290
R1270
R170
R744