Refrigerant Report - R744Refrigerant Report Introduction Perspectives in refrigerant development...

Revisions/supplements vs. 12th edition

This edition supersedes all previous issues.

Refrigerant Report

Introduction

Perspectives in refrigerant developmentAlternative refrigerants (overview)Global Warming and TEWI factor

HCFC refrigerantsR22 as transitional refrigerant

Chlorine free HFC refrigerantsR134a as a substitute for R12 and R22R152a – an alternative to R134a (?)R125, R143a and R32 as substances for refrigerant blends

Refrigerant blendsService blends as substitutes for R502 Service blends as substitutes for R12 (R500)Chlorine free R502 alternatives (blends)R404A and R507A as substitutes for R502R407A and R407B as substitutes for R502 R422A (ISCEON 79) as substitute for R502Chlorine free R22 alternatives (blends) R407C as substitute for R22R410A as substitute for R22 R417A and ISCEON 29 as substitutes for R22R419A (FX90) as substitute for R22

Halogen free refrigerantsNH3 (Ammonia) as substitute for R22R723 (NH3/DME) as an alternative to NH3

R290 (Propane) as substitute for R502 and R22Propylene (R1270) as an alternative to PropaneCO2 as an alternative refrigerant and secondary fluid

Special applications

Refrigerant properties

Application ranges – Lubricants

ContentsPage

3

346

77

99

1111

121415161617181919202121

222223242626

29

32

34

Introduction

Perspectives in refrigerant development

Stratospheric ozone depletion as well asatmospheric greenhouse effect due torefrigerant emissions have led to drasticchanges in the refrigeration and air conditioning technology since the begin-ning of the 90s.

This is especially true for the area of com-mercial refrigeration and A/C plants withtheir wide range of applications. Until afew years ago the main refrigerants usedfor these systems were ozone depletingtypes, namely R12, R22 and R502; forspecial applications R114, R12B1, R13B1,R13 and R503 were used.

With the exception of R22 the use ofthese chemicals is not allowed any morein industrialised countries. In the Euro-pean Union, however, there is a currentearly phase-out for R22 as well whichshall be realised step by step (see page 7for explanations). The main reason for this early ban of R22contrary to the international agreement isthe ozone depletion potential although itis only small.

Due to this situation enormous conse-quences result for the whole refrigerationand air conditioning trade. BITZER there-fore committed itself to taking a leadingrole in the research and development ofenvironmentally benign system designs.

Although the chlorine free HFC refriger-ants R134a, R404A, R507A, R407C,R410A as well as NH3 and various hydro-carbons have already become estab-lished, there are still further tasks to per-form, especially with respect to the globalwarming impact. The aim is to significant-ly reduce direct emissions caused byrefrigerant loss, and indirect emissionsthrough highly efficient plants.

Therefore a close co-operation exists withscientific institutions, the refrigeration andoil industries, component manufacturersas well as a number of innovative refriger-ation and air conditioning companies.

A large number of development taskshave been completed; an extensive rangeof compressors and equipment is alreadyavailable for the various alternative refrig-erants.

Besides the development projects BITZERactively supports legal regulations andself commitments concerning the respon-sible use of refrigerants (see also page 6).

The following report deals with possibili-ties for a short and medium term changeto environmentally benign refrigerants inmedium and large commercial refrigera-tion and A/C plants. At the same time, theexperience which already exists is alsodealt with and the resulting consequencesfor plant technology.

❄ ❄ ❄

The results of serveral studies confirmthat the vapour compression refrigerationplants normally used in the commer-cial field are far superior to all other pro-cesses down to a cold space temperatureof around -40°C.

The selection of an alternative refrigerantand the system design receives specialsignificance, however. Besides the requestfor substances without ozone depletionpotential (ODP=0) especially the energydemand of a system is seen as an essen-tial criterion due to its indirect contribu-tion to the greenhouse effect. On top ofthat there is the direct ozone depletionpotential (GWP) due to refrigerant emission.

Therefore a calculation method has beendeveloped for the qualified evaluation of asystem which enables an analysis of thetotal influence on the greenhouse effect.

In this connection the so-called „TEWI“factor (Total Equivalent Warming Impact)has been introduced, the result is howe-ver mainly dependent upon the CO2 emis-sion from the energy generation or drivemethod employed (further information onpage 6).

Therefore it is possible that in future theassessment of refrigerants with regard tothe environment could differ according tothe place of installation and drive method.

A closer look on the HFC based substitu-tes shows, however, that the possibilitiesfor directly comparable single substancerefrigerants are limited. The situation forR12 with the substitute R134a is relativelyfavourable, as it is for R502 with the alter-natives R404A and R507A. It is more criti-cal for alternatives to other CFC refrige-rants and also for HCFCs, e.g. R22.

The refrigerants R32, R15 and R134a areregarded as direct substitutes from theline of HFCs. These however can only beused exceptionally as a pure substancedue to their specific characteristics. Mostimportant criteria in this concern are flam-mability, thermodynamic properties andglobal warming potential. These substan-ces are much more suitable as compo-nents of blends where the individual cha-racteristics can be matched to therequirements according to the mixing pro-portions.

Besides HFC refrigerants, Ammonia (NH3)and hydrocarbons are considered as sub-stitutes as well. The use for commercialapplications, however, is limited by strictsafety requirements.

Carbon dioxide (CO2) becomes moreimportant as an alternative refrigerant andsecondary fluid, too. Due to its specificcharacteristics, however, there are restric-tions to a general application.

The illustrations on the next pages show astructural survey of the alternative refrige-rants and a summary of the single orblended substances which are now avai-lable. After that the individual subjects arediscussed.

Due to the increasing interest in substitu-tes for R114, R12B1, R13B1, R13 andR503, the possible alternatives are alsoconsidered in this report.

Refrigerant data, application ranges andlubricant specifications are shown onpages 32 to 35.

For reasons of clarity the less or onlyregionally known products are not speci-fied in this issue, which is not intended toimply any inferiority.

3

4

Previous Alternativesrefrigerants

ASHRAE Trade name Composition DetailedClassification (with blends) Information

R401A MP39 DuPont R22/152a/124R401B MP66 DuPont R22/152a/124 pagesR12 R409A FX56 Atofina/Solvay R22/124/142b 15, 32...35(R500) R409B FX57 Atofina R22/124/142bR413A ISCEON 49 Rhodia R134a/218/600a

R22 – – –R402A HP80 DuPont R22/125/290 pagesR402B HP81 DuPont R22/125/290 7, 8, 14, 15,R502 R403A ISCEON 69S Rhodia R22/218/290 32...35R403B ISCEON 69L Rhodia R22/218/290R408A FX10 Atofina R22/143a/125

R114 R124 – – pagesR12B1 R142b – – 29, 32...35

R13B1R13 Alternatives see Fig. 3 “Chlorine free HCFC Refrigerants”R503

Fig. 2 Alternatives for CFC refrigerants (transitional / service refrigerants)

Fig. 1 General survey of the alternative refrigerants

3

3

4

1


SingleSubstances

e.g. R22R123R124R142b

Blends

predominantlyR22-Based

HCFC/HFC- partly chlorinated -

Transitional/ServiceRefrigerants

SingleSubstances

e.g. R134aR125R32R143aR152a

Blends

e.g. R404AR507AR407-SeriesR410A

HFC- chlorine free -

Medium and LongTerm Refrigerants

SingleSubstances

e.g. NH3

R290R1270R600aR170

Blends

e.g. R600a/R290

R290/R170R723

Halogen free

Alternative Refrigerants

Transitional / Service refrigerants 09.04

Previous AlternativesRefrigerants

ASHRAE Trade name Composition DetailedClassification (with blends) Information

R12 R134a–

pages(R500) R152a 9...11, 32...35

R404A various R143a/R125/R134a

R502 R507A R143a/125 pagesR407A, R407B KLEA 407A, 407B INEOS Fluor R32/125/134a 16...18, 32...35R422A ISCEON 79 Rhodia R125/134a/600a

R407C various R32/125/134aR410A various R32/125 pagesR417A ISCEON 59 Rhodia R125/134a/600 19...21, 32...35– ISCEON 29 Rhodia R125/134a/600aR419A FX90 Atofina R125/R134a/R-E170

R114 R236fa – – pagesR12B1 R227ea – – 29, 32...35

R410A various R32/125 pagesR13B1 – FX 80 Atofina R32/125 29, 30, 32...35– ISCEON 89 Rhodia R125/218/290

R13 R23 – – pagesR503 R508A KLEA 508A INEOS Fluor R23/116 30, 32...35R508B Suva95 DuPont R23/116

1

R22

5

Chlorine free HFC refrigerants and blends (long term alternatives) 09.04

Fig. 3 Alternatives for CFC and HCFC refrigerants (chlorine free HFC refrigerants)

Fig. 4 Alternatives for CFC and HCFC refrigerants (halogen free refrigerants)

Explanation of Fig. 2 to 4 inflammable large deviation in refrigerating capacity and chlorine free service refrigeranttoxic pressures to the previous refrigerant Azeotrope


3 41

2 5

Previous AlternativesRefrigerants

ASHRAE Trade name Formula DetailedClassification Information

R12 R290/600a – C3H8/C4H10 pages(R500) R600a – C4H10 24, 32...35

R717 – NH3 pagesR502 R290 – C3H8 22...26, 32...35R1270 – C3H6

R717 – NH3

R22R723 – NH3 + R-E170 pagesR290 – C3H8 22...26, 32...35R1270 – C3H6

R114R600a – C4H10

pagesR12B1 29, 32...35

R13B1 keine direkte Alternative verfügbar

R13R170 – C2H6

pagesR503 30, 32...35

Diverse R744 – CO2pages26, 28, 32...35

Halogen free refrigerants (long term alternatives) 09.04

3

3

1

1

1

1

1

1

1

1

1

1

2

2

1 2 5

6

Fig. 6 Comparison of TEWI figures (Example)

Global Warming andTEWI Factor

TE

WI

x 1

03

Refrigerant charge [m]10kg 25kg 10kg 25kg

recoverylosses

300

200

100

RL

RL

RL

RL

ENERGY

ENERGY

ENERGY

ENERGY

Comparisonwith 10% higher

energy consumtion

LL

RL = Impact of

leakageLL = Impact of

lossesLL LL

LL

+10%

+10%

As already mentioned in the introduction amethod of calculation has been developed,with which the influence upon the globalwarming effect can be judged for the opera-tion of individual refrigeration plants (TEWI = Total Equivalent Warming Impact).

All halocarbon refrigerants, including thenon-chlorinated HFCs belong to the cate-gory of the greenhouse gases. An emis-sion of these substances contributes tothe global warming effect. The influence ishowever much greater in comparison toCO2 which is the main greenhouse gas inthe atmosphere (in addition to watervapour). Based on a time horizon of 100years, the emission from 1 kg R134a is forexample roughly equivalent to 1300 kg ofCO2 (GWP100 = 1300). It is already appar-ent from these facts that the reduction ofrefrigerant losses must be one of the maintasks for the future.

On the other hand, the major contributorto a refrigeration plant’s global warmingeffect is the (indirect) CO2 emissioncaused by energy generation. Based onthe high percentage of fossil fuels used inpower stations the average European CO2release is around 0.6 kg per kWh of elec-trical energy. A significant greenhouseeffect occurs over the lifetime of the plantas a result of this.

In addition to this an example in Fig. 6(medium temperature with R134a) showsthe influence upon the TEWI value withvarious refrigerant charges, leakage los-ses and energy consumptions.

This example is simplified based on anoverall leak rate as a percentage of therefrigerant charge. As is known the practi-cal values vary very strongly whereby thepotential risk with individually constructedsystems and extensively branched plantsis especially high.

Great effort is taken worldwide to reducegreenhouse gas emissions and legal regulations have partly been developedalready. For the EU territory a “Regulationon Fluorinated Gases” is presently in process, which is likely to become legalfor the member states in 2005.

TEWI = TOTAL EQUIVALENT WARMING IMPACT

TEWI = ( GWP x L x n ) + ( GWP x m [ 1- α recovery ] + ( n x Eannual x β )

Leakage Recovery losses

direct global warming potential

Energy consumption

indicrect globalwarming potential

GWP = Global warming potantialL = Leakage rate per yearn = System operating timem = Refrigerant chargeα recovery = Recycling factorEannual = Energy consumption per yearβ = CO2-Emission per kWh

[ CO2-related ][ kg ][ Years ][ kg ]

[ kWh ](Energy-Mix)

TEWI = TOTAL EQUIVALENT WARMING IMPACT

ExampleMedium temperature R134a

SST -10 °CSCT +40 °Cm 10 kg // 25 kgL[10%] 1 kg // 2,5 kgCAP 13,5 kW E 5 kW x 5000 h/aβ 0,6 kg CO2/kWhα 0,75n 15 yearsGWP 1300 (CO2 = 1)

time horizon 100 years

As this is a high proportion of the totalbalance it is also necessary to place anincreased emphasis upon the use of highefficiency compressors and associatedequipment as well as optimized systemcomponents, in addition to the demandfor alternative refrigerants with favourable(thermodynamic) energy consumption.

When various compressor designs arecompared, the difference of indirect CO2emission (due to the energy requirement)can have a larger influence upon the totaleffect as the refrigerant losses.

A usual formula is shown in Fig. 5, theTEWI factor can be calculated and thevarious areas of influence are correspon-dingly separated.

Fig. 5 Method for the calculation of TEWI figures


7

HCFC Refrigerants

R22 as transitionalrefrigerant

Fig. 7 R12/R22 – Comparison of discharge gas temperatures ofa semi-hermetic compressor

Fig. 8 R12/R22/ R502 – Comparison of pressure levels

Despite of the generally favourable prop-erties R22 is already subject to variousregional restrictions* which control theuse of this refrigerant in new systems andfor service purposes due to its ozonedepletion potential – although being low.

With regard to components and systemtechnology a number of particularities areto follow as well. Refrigerant R22 hasapproximately 55% higher refrigeratingcapacity and pressure levels in compari-son to R12. The significantly higher dis-charge gas temperature is also a criticalfactor compared to R12 (see Fig. 7) andR502.

Suitable compressors are required forplants with R22, these have been avail-able and are proven for medium tempera-ture and air conditioning for a long time.

Refrigeration and air conditioning in vehi-cles – such as cars, trucks, buses andtrains – are more problematic. The higherpressure and temperature levels of R22seriously limit here the range of applica-tion. Only some of the applications cantherefore be covered.

Also critical – due to the high dischargegas temperature – are low temperatureplants especially concerning thermal sta-bility of oil and refrigerant, with the dan-ger of acid formation and copper plating.Special measures have to be adoptedtherefore, such as two stage compres-sion, controlled refrigerant injection, addi-tional cooling, monitoring of dischargegas temperature, limiting the suction gassuperheat and particularly careful installation.

* Not allowed for new equipment in Germany andDenmark since 2000 January 1st and in Swedenas of 1998.Since January 1st, 2001 restrictions apply to theother member states of the EU as well. The mea-sures concerned are defined in the new ODSRegulation 2037/2000 of the EU commision onozone depleting substances. This regulation alsogoverns the use of R22 for service reasons withinthe entire EU.

Information about the world wide R22 phase-out regulation can be found underwww.arap.org/docs/regs.html as well.

Dis

char

ge g

as t

emp

. [˚C

]

Evaporation [˚C]

80

170

-40 0 10-30 -20 -10

90

160

150R12tc +60

R22tc +60tc +50

tc +50

tc +40

tc +40

100

110

120

130

140

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

R12

R22

R502

2

4020

Although the chlorine free substitutesR134a and R404A/R507A (Fig. 1 and 3) haveextensively made their way as alternativesto R12 and R502, in many internationalfields R22 is still used in new installationsand for retrofitting of existing systems.

Reasons are relatively low investmentcosts, especially compared with R134asystems, but also in its large applicationrange, favourable thermodynamic proper-ties and low energy requirement. Addi-tionally there is world wide availability ofR22 and the proven components for it,which is not yet guaranteed everywherewith the chlorine free alternatives.

The latter is also true for the “zeotropic”service refrigerants (Fig. 1 and 2). More-over, they predominantly contain R22 andtherefore only make sense where pureR22 cannot be controlled due to highoperation temperatures. Related to thesemixtures special handling procedures arerequired (see section “Refrigerant blends”from page 12).

8

An incomparably wide palette is availa-ble from BITZER for use with R22:❏ Open and semi-hermetic reciproca-

ting compressors from 0.37 to 74 kWnominal motor power with specialdesign features for low temperatureuse– VARICOOL semi-hermetic (up to

5.5 kW)– Single stage semi-hermetic

with (up to 60 kW)– Two stage compressors

(up to 44 kW)❏ Open and semi-hermetic screw com-

pressors from 15 to 220 kW nominalmotor power (parallel operation to400 kW) for single and two stagesystems.

Converting existing plants

Existing R12 plants can only subsequentlybe converted to R22 under restrictionswithout exchanging major components.Even if the compressor, heat exchangerand pressure vessel are suitable for oper-ation with R22, the refrigeration capacityand energy requirement (with identicalcompressor displacement) are significant-ly higher after the conversion. The tempe-rature differences at the evaporator andcondenser will be much greater andabnormal or critical operating conditionscould even occur.

The installation of a compressor with asmaller displacement (same capacity aswith R12) could on the other hand lead to

unstable operation of the evaporator andoil migration due to the reduced flowvelocities.

R502 plants can in many cases be con-verted to R22 with reasonable effort. Theindividual components must however bechecked for suitability and possibly bemodified or exchanged.In this connection the significantly lowermass flow of R22 must also be considered.

®

HCFC Refrigerants

Supplementary BITZER information(see also http://www.bitzer.de)

❏ Technical Information KT-650“Retrofitting of R12 and R502 refrigerating systems to alternative refrigerants”

R134a as substitute forR12 and R22

9

Chlorine free HFC refrigerants

Fig. 9/1 R134a/R12 – Comparison of performance data of a semi-hermetic compressor

Fig. 9/2 R134a/R22 – Comparison of performance data of a semi-hermetic compressor

Rel

atio

n R

134a

to

R12

(=10

0%)

Evaporation [˚C]

80

110

0 10

90

100

COP

Qo

85

95

105

-30 -20 -10

t c 5

0˚C

tc 50˚C

tc 40˚C

toh 20˚C

t c 4

0˚C

Rel

atio

n R

134a

to

R22

(=10

0%)

Evapration [˚C]

50

110

10 20

70

COP

Qo

60

80

100

-20 -10 0

toh 20˚C

90

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

Comprehensive tests have demonstratedthat the performance of R134a exceedstheoretical predictions over a wide rangeof compressor operating conditions. Temperature levels (discharge gas, oil) areeven lower than with R12 and, therefore,substantially lower than R22 values. Thereare thus many potential applications inair-conditioning and medium temperaturerefrigeration plants. Good heat transfercharacteristics in evaporators and condensers (unlike zeotropic blends)favour particularly an economical use.

Lubricants for R134a and other HFCsThe question of a suitable lubricant forR134a (and other HFCs described in thefollowing) has been found to be a pro-blem. The traditional mineral and synthe-tic oils are not miscible (soluble) withR134a and are therefore only insufficientlytransported around the refrigeration circuit.Immiscible oil can settle out in the heatexchangers and prevent heat transfer tosuch an extent that the plant can no lon-ger be operated.

New lubricants were developed with theappropriate solubility and have now –after a long test phase – been in use for

several years. These lubricants are basedon Polyol Ester (POE) and PolyalkyleneGlycol (PAG).They have similar lubrication characteri-stics to the traditional oils, but are moreor less hygroscopic, dependent upon therefrigerant solubility. This demands special care during manu-facturing (including dehydrating), trans-port, storage and charging, to avoid che-mical reactions in the plant, such ashydrolysis.

PAG based oils are especially critical withrespect to water absorption. Moreover,they have a relatively low dielectricstrength and for this reason are not verysuitable for semi-hermetic and hermeticcompressors. They are therefore mainlyused in car A/C systems with open com-pressors, where specific demands areplaced on lubrication and optimum solubi-lity is required because of the high oil cir-culatation rate. In order to avoid copperplating, no copper containing materialsare used in these systems either.

The rest of the refrigeration industry pre-fers ester oils, for which extensive expe-rience is already available. The results aregenerally positive when the water contentin the oil does not much exceed 100 ppm.

R134a was the first chlorine free (ODP=0)HFC refrigerant that was tested compre-hensively. It is now used world-wide inmany refrigeration and air-conditioningunits with good results. As well as beingused as a pure substance R134a is alsoapplied as a component of a variety ofblends (see “Refrigerant blends”, page 12).

R134a has similar thermodynamic pro-perties to R12: refrigeration capacity,energy requirement, temperature proper-ties and pressure levels are comparable,at least in air-conditioning and mediumtemperature refrigeration plants. This refri-gerant can therefore be used as an alter-native for most R12 applications.

For some applications R134a is evenpreferred as a substitute for R22, animportant reason being the limitations tothe use of R22 in new plants. However,the lower volumetric refrigeration capacityof R134a (see Fig. 9/2) requires a largercompressor displacement than with R22.There are also limitations in the applica-tion with low evaporating temperatures tobe considered.

Fig. 10 R134a/R12/R22 – Comparison of pressure levels

10

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

R12

R22

R134a

2

4020

Supplementary BITZER informationconcerning the use of R134a(see also http://www.bitzer.de)

❏ Technical Information KT-620“HFC-Refrigerant R134a”

❏ Technical Information KT-650“Retrofitting of R12 and R502 refrigerating systems to alternativerefrigerants”

❏ Technical Information KT-510“Polyolester oils for reciprocatingcompressors”

However, for buses and commercial vehi-cles, alternatives are being examined ashygroscopic lubricants lead to increasedrisks due to the permeability of hoses andpartly through inadequate servicing. Analternative to this are the (almost) non-soluble alkylates where the flow and lubri-cating characteristics are improved byadditives. There are already positive oper-ating results, however, practical imple-mentation requires individual adaptationand system trials.

In the meantime, factory made A/C andcooling units are increasingly being charged with Polyvinyl Ether (PVE) oils.Although they are even more hygroscopicthan POE, on the other hand they are veryresistant to hydrolysis, thermally and che-mically stable, possess good lubricatingproperties and high dielectric strength.Unlike POE they do not tend to formmetal soap and thus the danger of capil-lary clogging is reduced.

Resulting design and construction criteria

Suitable compressors are required forR134a with a special oil charge, andadapted system components.

The normal metallic materials used in CFCplants have also been proven with esteroils; elastomers must sometimes be matched to the changing situation. This isespecially valid for flexible hoses wherethe requirements call for a minimum residual moisture content and low perme-ability.

The plants must be dehydrated with par-ticular care and the charging or changingof lubricant must also be done carefully.In addition relatively large driers shouldbe provided, which have also to bematched to the smaller molecule size ofR134a.

As the result of many years experiencein close cooperation with the oil indu-stry, BITZER can offer the whole pro-gram of reciprocating, screw and scrollcompressors for R134a – including thesuitable oil. Positive experience hasbeen gained with a large number ofrefrigeration and air-conditioning plantsof different designs.

Converting existing R12 plants

At the beginning this subject had beendiscussed very controversially, severalconversion methods were recommendedand applied. Today there is a generalagreement on technically and economical-ly matching solutions.

Here, the characteristics of ester oils arevery favourable. Under certain conditionsthey can be used with CFC refrigerants,they can be mixed with mineral oils andtolerate a proportion of chlorine up to afew hundred ppm in an R134a system.

The remaining moisture content hashowever an enormous influence. Theessential requirement therefore exists forvery thorough evacuation (removal ofremaining chlorine and dehydration) andthe installation of generously dimensioneddriers. Doubtful experience has also beenfound, with systems where the chemicalstability was already insufficient with R12operation e.g. with bad maintenance,small drier capacity, high thermal loading.The increased deposition of oil decompo-sition products containing chlorine oftenoccurs here. These products are releasedby the working of the highly polarizedmixture of ester oil and R134a and findtheir way into the compressor and regulat-ing devices. Conversion should thereforebe limited to systems which are in a goodcondition.Meanwhile, corresponding conversionprocedures have been proven, but individ-ual adaptation may be required in certaincases.


11


safety measures along with the corre-sponding risk analysis.

The drawback in case of greater pressureratios is the comparatively high compres-sor discharge gas temperature which liesbetween the levels of R134a and R22,known for its high thermal loading (Fig.11). This presents an added difficulty forthe extreme operating conditions in auto-motive air-conditioning units – consideringalso the chemical stability of the circuitand the lubricants. The oils used forR134a are likewise suitable as lubricants.

A final judgment of the application ofR152a is not possible at this time, furtherdevelopments will be reported uponaccordingly.

R125, R143a and R32 likewise belong tothe chlorine free (ODP=0) alternatives,whereas the latter two are flammable(safety group A2) and are therefore nodirect substitutes for (H)CFC refrigerants.R32, moreover, is characterised by veryhigh pressure levels and discharge gastemperatures.

R125, on the other hand, is non-flamma-ble, the boiling point lies at -48.5°C andthe adiabatic exponent is comparativelylow. At least from this viewpoint, there aresimilar conditions to the previously oftenused R502. The disadvantages of R125,however, are the steep pressure slopewith resulting higher pressure ratios and avery low critical temperature of 66°C.Applications with air-cooled condensersare thereby restricted and the energy effi-ciency at high condensing temperatures isrelatively poor.

For the reasons stated before, the abovementioned refrigerants are not or onlyused in exceptional cases as pure sub-stances. On the other hand, they can beblended into mixtures – also with additio-nal substances such as R134a – for adefined application profile (see next topic“Refrigerant blends”).

R152a – an alternative to R134a (?)

Abb. 11 R134a/R152a/R22 – Comparison of discharge gas temperatures Abb. 12 R125/R143a/R32 – Comparison of pressure levels

Dis

char

ge g

as t

emp

erat

ure

[˚C

]

Evaporation [˚C]

10-20 060

140

100

80

160

tc

∆ tohη

50°C10K0,6

R22

R134a

R152a

-10-30

120

Pre

ssur

e [b

ar]

Temperature [˚C]

1

40

0 60

6

15

4

10

20

-40 -20

R32

R143a

2

4020

R125

30

8

Compared to R134a, R152a is very similarwith regard to volumetric cooling capacity(approx. -5%), pressure levels (approx. -10%) and energy efficiency. Mass flow,vapour density and thus also the pressuredrop are even more favourable (approx. -40%).

R152a has been used for many years as acomponent in blends but not as a singlesubstance refrigerant till now. Especiallyadvantageous is the very low global warming potential (GWP=140 / compareR134a: GWP=1300). This is the main rea-son why R152a is discussed as an alter-native to R134a in automotive air condi-tioners for quite some time. It is knownthat mobile units with open drive com-pressors and hose connections in therefrigerant circuit pose a higher risk ofleakage than stationary systems, with thepotential threat of direct emissions contri-buting to the global warming effect.

As already mentioned, however, R152a isinflammable – due to its low fluorine con-tent – and classified in safety group A2.As a result, increased safety requirementsdemand individual design solutions and

R125, R143a and R32 as components for refrigerant blends

Refrigerant blends have been developedfor existing as well as for new plants withproperties making them comparable alter-natives to the previously used substances.

Although the situation is now less complex,the range on offer is nevertheless still veryextensive.

It is necessary to distinguish between twocategories:

1. Transitional or service blendsMost of these blends contain HCFC R22as the main constituent. They are prima-rily intended as service refrigerants forexisting plants where limitations withR12, R502 and other CFCs are to beexpected (for details of availability andlegal regulations see also page 7). Cor-responding products are offered by vari-ous manufacturers, the practical experi-ence covering the necessary steps ofconversion procedure are mainly avail-able.

2. Chlorine free HFC blends These are long term substitutes for therefrigerants R502, R22, R13B1 andR503. Above all, R404A and R507A arealready being used to a great extent.

Two and three component blends alreadyhave a long history in the refrigerationtrade. A difference is made between the socalled “azeotropes” (e.g. R502) with thermodynamic properties similar to singlesubstance refrigerants, and “zeotropes”with “gliding” phase changes (see also nextsection). The development of “zeotropes”was mainly concentrated on special appli-cations in low temperature and heat pumpsystems. Actual system constructionremained however the exception.

A somewhat more common earlier practicewas the mixing of R12 to R22 in order toimprove the oil’s return flow and to reducethe discharge gas temperature with higherpressure ratios. It was also usual to add R22to R12 systems for improved performance,

12

Refrigerant blends or to add hydrocarbons in the extra lowtemperature range for a better oil transport.

This possibility of specific “formulation” ofcertain characteristics was indeed themain starting point for the development ofa new generation of blends.

As already mentioned earlier, no directlycomparable substitute for R502 and R22is available from the chlorine free singlesubstance series of alternative refriger-ants. A similar situation can be stated forR13B1 and R503.

If flammability is unacceptable, and toxi-cological certainty is required and in addi-tion, application range, COP, pressure andtemperature conditions are to be compar-able, the only substitutes which remainfor the long term, in addition to R134a forR12, are blends.

Substitutes for R502 have first priority,as it was used in larger quantities and isalready effected by the phase-out regula-tions in many countries. The following discussion therefore, deals first with theestablished alternatives for this refrigerantand the results from the extensive appli-cations in real systems.

Another focal point are alternatives forR22.

BITZER has already accumulatedextensive experience with the new gen-eration of blends. Laboratory and fieldtesting was commenced at an earlystage so that basic information wasobtained for the optimizing of the mix-ing proportions and for testing suitablelubricants. Based on this data, a large supermarket plant – with 4semi-hermetics type 4G-20.2 in parallel– could already be commissioned atthe start of ‘91. Even after long periods of use therewere no signs of abnormal wear of thecompressor or chemical reactions inthe circuit.

General characteristics of zeotropicblends

As opposed to azeotropic blends (e.g.R502, R507A), which behave as singlesubstance refrigerants with regard toevaporation and condensing processes,the phase change with zeotropic fluidsoccurs in a “gliding” form over a certainrange of temperature.

This “temperature glide” can be more orless pronounced, it is mainly dependentupon the boiling points and the percent-age proportions of the individual compo-nents. Certain supplementary definitionsare also being used, depending on theeffective values, such as “near-azeotrope”or “semi-azeotrope” for less than 1 Kglide.

This means in practice already a smallincrease in temperature in the evaporationphase and a reduction during condensing.In other words, based on a certain pres-sure the resulting saturation temperaturesdiffer in the liquid and vapour phases (Fig. 13).

To enable a comparison with single sub-stance refrigerants, the evaporating andcondensing temperatures have beenmostly defined as mean values. As a con-sequence the measured subcooling andsuperheating conditions (based on meanvalues) are unreal. The effective result –related to dew and bubble temperature –is less in each case.

These factors are very important whenassessing the minimum superheat at thecompressor inlet (usually 5 to 7 K) and thequality of the refrigerant after the liquid receiver.

With regard to a uniform and easily com-prehensible definition of the rated com-pressor capacity, the revised standardsEN12900 and ARI540 will be applied.Evaporating and condensing temperaturesrefer to saturated conditions (dew points).

❏ Evaporating temperature according topoint A (Fig. 13).

❏ Condensing temperature according topoint B (Fig. 13).

Refrigerant blends

13

Refrigerant blends

Fig. 13 Evaporating and condensing behavior of zeotropic blends Fig. 14 Pressure levels of blends in comparison to R502

Pre

ssur

e

Enthalpy

Temperature glideMean condensing temperatureMean evaporating temperature

∆tgtcmtom

CC1

DD1

A A1

B B1

Isotherms

∆tg

∆tgtcm

tom

Bubbl

e Li

ne

Dew

line

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

1

20

10

2

4

6

R404A

R502R403B

Also in this case the assessment of theeffective superheating and subcoolingtemperatures will be simplified.

It must however be considered that theactual refrigeration capacity of the sys-tem can be higher than the rated com-pressor capacity. This is partly due to aneffectively lower temperature at the evap-orator inlet.

A further characteristic of zeotropicrefrigerants is the potential concentrationshift when leakage occurs. Refrigerantloss in the pure gas and liquid phases ismainly non-critical. Leaks in the phasechange areas, e.g. after the expansionvalve, within the evaporator and con-denser/ receiver are considered more sig-nificant. It is therefore recommended thatsoldered or welded joints should be usedin these sections.

Extended investigations have in themeantime shown that the effect of leak-age leads to less serious changes in con-centration than was previously thought. Itis in any case certain that the following

substances which are dealt with herecannot develop any flammable mixtures,either inside or outside the circuit. Essen-tially similar operating conditions andtemperatures as before can only beobtained by supplementary charging withthe original refrigerant in the case of asmall temperature glide.

Further conditions/recommendations concerning the practical handling ofblends must also be considered:

❏ The plant always has to be chargedwith liquid refrigerant. When vapour istaken from the charging cylinder shiftsin concentrations may occur.

❏ Since all blends contain at least oneflammable component, the entry of airinto the system must be avoided. A critical shift of the ignition point can occur under high pressure and evacu-ating when a high proportion of air is present.

❏ The use of blends with a significanttemperature 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.

These refrigerants belong to the group of“Service blends” and are offered underthe designations R402A/R402B* (HP80/HP81 – DuPont), R403A/R403B* (“Isceon”69S/69L – Rhodia) and R408A* (“Forane”FX10 – Atofina).

The basic component is in each caseR22, the high discharge gas temperatureof which is significantly reduced by theaddition of chlorine free substances withlow isentropic compression exponent (e.g. R125, R143a, R218). A characteristicfeature of these additives is an extraordi-narily high mass flow, which enables themixture to achieve a great similarity to R502.R290 (Propane) is added as the thirdcomponent to R402A/B and R403A/B toimprove miscibility with traditional lubri-cants as hydrocarbons have especiallygood solubility characteristics.

For these blends two variations are offeredin each case. When optimizing the blend

variaions with regard to identical refrigerat-ion capacity as for R502 the laboratorymeasurements showed a significantlyincreased discharge gas temperature (Fig.15), which above all, with higher suctiongas superheat (e.g. supermarket use)leads to limitations in the application range.

On the other hand a higher proportion ofR125 or R218, which has the effect ofreducing the discharge gas temperatureto the level of R502, results in somewhathigher cooling capacity (Fig. 16).

With regard to material compatibility theblends can be judged similarly to (H)CFCrefrigerants. The use of conventional refri-geration oil (preferably semi or full synthetic)is also possible due to the R22 and R290proportions.

Apart from the positive aspects there arealso some disadvantages. These substan-ces can also only be seen as alternativesfor a limited time. The R22 proportion has (although low) an ozone depletion potential.The additional components R125, R143aand R218 still have a comparatively highglobal warming potential.

Resulting design criteria/Converting existing R502 plants

The compressor and the componentswhich are matched to R502 can remain inthe system in most cases. The limitationsin the application range must however beconsidered: Higher discharge gas temper-ature as for R502 with R402B**, R403A**and R408A** or higher pressure levelswith R402A** and R403B**.

Due to the good solubility characteristicsof R22 and R290 an increased dangerexists, that after conversion of the plant,possible deposits of oil decompositionproducts containing chlorine may be dis-solved and find their way into the com-pressor and regulating devices. Systemswhere the chemical stability was alreadyinsufficient with R502 operation (badmaintenance, low drier capacity, high

* When using blends containing R22, legal regulations are to be observed, see also page 7.

** Classification according to ASHRAE nomenclature

14

Service blends with thebasic component R22* assubstitutes for R502

Fig. 15 Effect of the mixture variation upon the discharge gas temperature (Example: R22/R218/R290)

Fig. 16 Comparison of the performance data of a semi-hermetic compressor

Dis

char

ge g

as t

emp

. [˚C

]

Content of R218 [%]

170

0 6020 40

165

150

115

120

130

140

R40

3A

R40

3B

R502

totctoh

R22

-35°C40°C20°C

145

155

135

125

160

Com

par

ison

of p

erfo

rman

ce 110

105

100

95

90

85

[%]

totctoh

-35°C40°C20°C

115

Qo COP

R50

2

R40

2A (

HP

80)

R40

2B (

HP

81)

R40

3B (

69L

)

R40

3A (

69S

)

R40

8A (

FX

10)

R40

3B (

69L

)

R40

3A (

69S

)

R40

8A (

FX

10)

R50

2

R40

2A (

HP

80)

R40

2B (

HP

81)

Service blends

15

Service blends

The basic suitability of BITZER com-pressors has already been establishedby laboratory and field tests. Howeveras the result of a conversion is verymuch dependent upon the previouscondition of the plant (see above expla-nation), the judgement of a possibleguarantee claim must be made subjectto the examination of the compressor.

thermal loading) are particularly at risk.Before conversion generously dimen-sioned suction gas filters and liquid linedriers should therefore be fitted for clean-ing and after approximately 100 hoursoperation an oil change should be made;further checks are recommended.

The operating conditions with R502(including discharge gas temperature andsuction gas superheat) should be notedso that a comparison can be made withthe values after conversion. Dependingupon the results regulating devices shouldpossibly be reset and other additionalmeasures should be taken as required.

Resulting design criteria/Converting existing R12 plants

Compressors and components can mostlyremain in the system. However, whenusing R413A the suitability must bechecked against R134a. The actual “retro-fit” measures are mainly restricted to changing the refrigerant (possibly oil) anda careful check of the superheat setting ofthe expansion valve. A significant temper-ature glide is present due to the relativelylarge differences in the boiling points ofthe individual substances (Fig. 33, page33), which demands an exact knowledgeof the saturation conditions (can be found from vapour tables of refrigerantmanufacturer) in order to assess theeffective suction gas superheat.

In addition the application range mustalso be observed.Different refrigerant types are required forhigh and low evaporating temperatures ordistinct capacity differences must be con-sidered (data and application ranges seepages 32 to 35). This is due to the steepercapacity characteristic, compared to R12.

Due to the partially high proportion of R22especially with the low temperature blends,the discharge gas temperature with somerefrigerants is significantly higher thanwith R12. The application limits of thecompressor should therefore be checkedbefore converting.The remaining application criteria are simi-lar to those for the substitute substancesfor R502 which have already been men-tioned.

„“

Supplementary BITZER informationconcerning the use of retrofit blends(see also http://www.bitzer.de)

❏ Technical Information KT-650 “Retrofitting of R12 and R502refrigerating systems to alternative refrigerants”

Although as experience already shows,R134a is also well suited for the conver-sion of existing R12 plants, the generaluse for such a “retrofit” procedure is notalways possible. Not all compressorswhich have previously been installed aredesigned for the application with R134a.In addition a conversion to R134a requiresthe possibility to make an oil change,which is for example not the case withmost hermetic type compressors.

Economical considerations also arise,especially with older plants where theeffort in converting to R134a is relativelyhigh. The chemical stability of such plantsis also often insufficient and therefore thechance of success is very questionable.Therefore “Service blends” are also avail-able for such plants as an alternative toR134a and are offered under the designa-tions R401A/R401B (MP39/MP66 –DuPont), R409A/B (FX56/FX57 – Atofinaand Solvay). The main components are the HCFCrefrigerants R22, R124 and/or R142b.Either HFC R152a or R600a (Isobutan) isused as the third component. Operationwith traditional lubricants (preferably semior full synthetic) is also possible due tothe major proportion of HCFC.

A further service blend is offered underthe designation R413A (ISCEON 49 –Rhodia). The constituents consist of thechlorine free substances R134a, R218 andR600a. In spite of the high R134a contentthe use of conventional lubricants is pos-sible because of the relatively low polarityof R218 and the favourable solubility ofR600a. Oil migration may, however, resultin systems with a high oil circulation rateand/or a large liquid volume in the receiver.In such cases ester oil is recommended.

Service blends as substi-tutes for R12 (R500)

Supplementary BITZER informationconcerning the use of retrofit blends(see also http://www.bitzer.de)

❏ Technical Information KT-650“Retrofitting of R12 and R502 refrigerating systems to alternativerefrigerants”

These blends are substitutes which areabsolutely chlorine free (ODP=0) and aretherefore long term alternatives for R502.

A composition which was alreadylaunched at the beginning of ‘92 is knownunder the trade name „Suva“ HP62(DuPont). Long term use has shown goodresults.Further blends were traded as „Forane“FX70 (Atofina) and “Genetron” AZ50(Allied Signal) or “Solkane” 507 (Solvay).In the mean time HP62 and FX70 havebeen listed in the ASHRAE nomenclatureas R404A and AZ50 as R507A.

The basic components belong to the HFCgroup, where R143a belongs to the flam-mable category. Due to the combinationwith a relatively high proportion of R125the flammability is effectively counteract-ed and also in the case of leakage.

A feature of all three ingredients is thevery low isentropic compression exponent

16

Fig. 17 R404A/R502 – Comparison of discharge gas temperatures of a semi-hermetic compressor

Fig. 18 Comparison of performance data of a semi-hermetic compressor

Dis

char

ge g

as t

emp

. of R

404A

– r

elat

ive

diff

eren

ce t

o R

502

[K]

Evaporating [˚C]

-20-40 -30 -20 -10

tc 55°C

tc 40°C

toh 20°C

-10

0

+10

Com

par

ison

of p

erfo

rman

ce

100

95

90

80

[%] totctoh

-35°C40°C20°C

105

Qo

85

COP

R50

2

R40

4A

R50

7A

R50

2

R40

4A

R50

7A

R404A and R507A assubstitutes for R502

which results in a similar, with even a ten-dency to be lower, discharge gas temper-ature to R502 (Fig. 17). The efficient appli-cation of single stage compressors withlow evaporating temperatures is thereforeguaranteed.

Due to the similar boiling points for R143aand R125, with a relatively low proportionof R134a, the temperature glide with theternary blend R404A within the relevantapplication range is less than one Kelvin.The characteristics within the heatexchangers are not therefore very differentas with azeotropes. The results obtainedso far from heat transfer measurementsshow favourable conditions.

R507A is a binary substance combinationwhich even gives an azeotropic character-istic over a relatively wide range. The con-ditions therefore tend to be even better.

The performance found in laboratory tests (Fig. 18) gives hardly any differencebetween the various substances and showa large amount of agreement with R502.This justifies the good market penetrationof these substitutes.

Questions concerning material compatibil-ity are manageable; experience with otherHFCs justifies a positive assessment.

The newly developed POE oils can beused as lubricants; the suitability of vari-ous alternatives is being investigated aswell (see pages 9 and 10).

The relatively high global warming poten-tial (GWP100 = 3260… 3300) which ismainly determined by the R143a andR125 is something of a hitch. It is how-ever improved compared to R502(GWP100 = 5600) and which with regardalso to the favourable energy requirementleads to a reduction of the TEWI value.Other improvements are to be expected inthis respect due to further developed system control including for example thecontrolled lowering of the condensing tem-perature with low ambient temperatures.

Resulting design criteria

The system technology can be based onthe experience with R502 over a widearea. On the thermodynamic side, a heat

Chlorine free R502 alternatives (blends)

17


Supplementary BITZER informationconcerning the use of HFC blends(see also http://www.bitzer.de)

❏ Technical Information KT-630“HFC Refrigerant Blends”

❏ Technical Information KT-650 “Retrofitting of R12 and R502 refrigerating systems to alternativerefrigerants”

❏ Technical Information KT-510 “Polyolester oils forreciprocating compressors”

Alternatively to the earlier described sub-stitutes additional mixture versions havebeen developed based on R32 which ischlorine free (ODP=0) and flammable likeR143a.

The refrigerant R32 is also of the HFC typeand primarily seen as a candidate for R22alternatives (page 19). Due to the extentof the blend variations however comparablethermodynamic characteristics to R502can also be obtained.

Such kind of refrigerants were at first inthe market under the trade name KLEA60/61 (ICI) and are listed as R407A*/ R407B*in the ASHRAE nomenclature.

The necessary conditions, however, forR502 alternatives containing R32 are notquite as favourable compared to theR143a based substitutes as dealt withearlier. The boiling point of R32 is verylow at -52°C, in addition the isentropiccompression exponent is similarly high aswith R22. To match the characteristics ofR502 therefore requires relatively highproportions of R125 and R134a. The flam-mability of the R32 is thus effectively sup-pressed, at the same time the large differ-ences in the boiling points with a highproportion of R134a leads to a larger tem-perature glide.

The main advantage of R32 is the extraor-dinarily low global warming potential(GWP100 = 650) so that even in combina-tion with R125 and R134a it is significant-ly lower than with the R143a based alter-natives mentioned above.

Comprehensive measurements made withR32 containing blends in the BITZER lab-oratory do show certain capacity reduc-tions compared to R502 with low evapor-ating temperatures, the COP howevershows less deviation (Fig. 20). The TEWIvalues are relatively low, together with theadvantageous global warming potential.

Where these favourable prospects areconfirmed in real applications is subject tothe system criteria.

An important factor is the significant tem-perature glide which can have a negativeinfluence upon the capacity/temperaturedifference of the evaporator and condenser.In order to closer examine this factorinvestigations concerning the behaviour of heat exchangers (including design/con-struction) have already been carried out.

With regard to the material compatibility,R32 blends can be assessed similarly tothe HFC substitutes described before; thesame applies to the lubricants.

Despite the relatively high proportion ofR125 and R134a in the R32 blends aimedat R502 characteristics, the discharge gastemperature is somewhat higher than withthe R143a based alternatives. As a resultcertain limitations occur in the applicationrange.

From this point of view, but also withregard to the efficiency an intelligent con-trol is recommended for controlled float-ing of the condensing pressure with lowambient temperatures.

2-stage compressors can be applied veryefficiently where especially large lift con-ditions are found. An important advantagethereby is the use of a liquid subcooler.


The experience with R502 and R22 canbe used for the plant technology in manyrespects, considering the temperatureglide as well as the difference in the thermodynamic properties. This is espe-cially the case for designing and con-structing heat exchangers and expansionvalves.

The refrigerants are available. Occassion-ally, individual selection will be requiredfor the necessary components.

* Meanwhile, R407A/B have only limited availabilityin the market. Due to the historical development ofHFC blends they will, however, still be consideredin this Report.

exchanger between the suction and liquidline is recommended as this will improvethe refrigeration capacity and COP.

The availability of the refrigerants is guar-anteed.

Apart from laboratory investigationsBITZER has been co-ordinating a wideprogram of field tests to obtain the nec-essary operating experience over awide area for several years. BITZER offers the whole program ofreciprocating, scroll and screw com-pressors including the suitable oils forthese blends.

Converting existing CFC plants

Experience gained in investigative pro-grams shows that qualified conversionsare possible. However, major expendituremay be necessary depending on the sys-tem design.

R407A and R407B as substitutes for R502

18

Fig. 19 Comparison of discharge gas temperature of a semi-hermetic compressor

Fig. 20 Comparison of performance data of a semi-hermetic compressor

Dis

char

ge g

as te

mp.

of R

407A

/B –

rela

tive

diffe

renc

e to

R50

2 [K

]

Evaporation [˚C]

-10-40 -30 -20 -10

0

+10

+20

R407A

toh

R407B

40°Ctc

20°C

Com

par

ison

of p

erfo

rman

ce

Qo

100

95

90

75

[%] totctoh

-35°C40°C20°C

105

80

COP

R50

2

R40

7A

R40

7B

R50

2

R40

7A

R40

7B

BITZER offers a complete range of semi-hermetic reciprocating compressors –including suitable oil – for these blends.

Converting existing CFC plants

A comprehensive test program has beencompleted in which practicability wasproven. Because of the abovementionedcriteria, however, no general guidelinescan be established. Each case musttherefore be examined individually.

Supplementary BITZER informationconcerning the use of HFC blends(see also http://www.bitzer.de)

❏ Technical Information KT-630 “HFC Refrigerant Blends”

❏ Technical Information KT-650 “Retrofitting of R12 and R502 refrigerating systems to alternativerefrigerants”

❏ Technical Information KT-510“Polyolester oils forreciprocating compressors”


R422A (ISCEON 79 – Rhodia) was develo-ped with the goal of reaching a similarperformance and energy efficiency as withR404A and R507A but with a reduced glo-bal warming potential (GWP=2530).

This pertains to a zeotropic blend of thebasic components R125 and R134a with asmall addition of R600a. Due to its relati-vely high R134a percentage, the tempera-ture glide (Fig. 32) lies higher than forR404A, but lower than for R407A/B.

The adiabatic exponent, compared toR404A and R507A, is smaller and therefo-re the discharge gas and oil temperaturesof the compressor, too. Under extremelow temperature conditions this can beadvantageous. In cases of low pressureratio and suction gas superheat this canbe negative due to increased refrigerantsolution in the lubricant.

The material compatibility is comparableto the blends mentioned previously, thesame applies to the lubricants, as well.

R422A (ISCEON 79) as substitute for R502

On account of the good solubility ofR600a, conventional lubricants can alsobe used under favourable circumstances.Due to the usual application of this refri-gerant at low evaporating temperaturesPOE oils are more suitable especially forwidely branched systems.

From a thermodynamic point of view aheat exchanger between suction andliquid line is recommended, therebyimproving the cooling capacity and coeffi-cient of performance. Besides this theresulting increase in operating temperatu-res leads to more favourable lubricatingconditions (lower solubility).

Bitzer compressors are suitable forISCEON 79 in principle. An individualselection is possible upon demand.

As the HCFC refrigerant R22 (ODP=0.05)is still widely accepted only as a transi-tional solution, a number of chlorine-free(ODP=0) alternatives have been devel-oped and tested extensively. They arealready being used on a large range ofapplications.

Experience shows, however, that none ofthese substitutes can replace the refriger-ant R22 in all respects. Amongst otherthings there are differences in the volumet-ric refrigeration capacity, restrictions inpossible applications, special requirementsin system design or also considerably dif-fering pressure levels. So various alterna-tives come under consideration accordingto the particular operating conditions.

As well as the refrigerant R134a (page 9)the prefered alternatives are R32/R125/R134a, R32/R125 and R125/R134a/R600blends. The following description mainlyconcerns the development and potentialapplications of these. The halogen-freesubstitutes NH3, propane and propyleneas well as CO2 should also be considered,however, specific criteria must be appliedfor their use (described from page 22).

19


Fig. 21 R407C/R22 – Comparison of performance data of a semi-hermeticcompressor

Fig. 22 R407C/R22 – Comparison of pressure levels

Rel

atio

n R

407C

to

R22

(=10

0%)

Evaporation [˚C]

80

110

10 20

90

100

85

95

105

-20 -10 0

COP

Qo

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

toh 20˚C

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

1

20

10

2

4

6

R22

R407C

Chlorine free R22 alternatives

R407C as substitutefor R22

relatively low (GWP100 = 1520), which is agood presupposition for favourable TEWIvalues.

The high temperature glide is a disadvan-tage for usual applications which requiresappropriate system design and can havea negative influence on the efficiency ofthe heat exchangers (see explanations onpages 12/13).

Due to the properties mentioned, R407Cis preferably an R22 substitute for air-conditioning systems and (within certainlimitations) also for medium temperaturerefrigeration. In low temperature refrigera-tion, because of the high proportion ofR134a, a significant drop in coolingcapacity and COP is to be expected.There is also the danger of an increasedR134a concentration in the blend in evap-orators, with consequential reduction inperformance and malfunctioning of theexpansion valve (e.g. insufficient suctiongas superheat).

Material compatibility can be assessed assimilar to that of the blends discussed pre-viously; the same applies to the lubricants.

* Because of the high proportion (70%) of R134acontained in R407D this refrigerant cannot beregarded as an alternative to R22, but rather as asubstitute to R12 for low temperature cooling.

Blends of the HFC refrigerants R32, R125and R134a are seen as the favourite candidates for shortterm substitution forR22 – their performance and efficiencyare very similar (Fig. 21). At first twoblends of the same composition havebeen introduced under the trade namesAC9000 (DuPont) and KLEA66 (ICI). Theyare listed in the ASHRAE nomenclature as R407C. In the meantime there are alsofurther blend varieties (e.g. R407D*/ R407E)with somewhat differing compositions,whose properties have been optimized for particular applications.

Unlike the R502 substitutes with identicalblend components (see pages 17/18), theR22 substitutes under consideration con-tain higher proportions of R32 and R134a. A good correspondence with the proper-ties of R22 in terms of pressure levels,mass flow, vapour density and volumetricrefrigeration capacity is thus achieved. Inaddition, the global warming potential is

20


Fig. 23 R410A/R22 – Comparison of performance data of a semi-hermetic compressor

Fig. 24 R410A/R22 – Comparison of pressure levels

Rel

atio

n R

410A

to

R22

(=10

0%)

Evaporation [˚C]

80

150

10 20-20 -10 0

toh 20˚C

COP

Qo

tc 40˚C

tc 50˚C

tc 50˚C

tc 40˚C

90

140

130

120

110

100

Pre

ssur

e [b

ar]

Temperature [˚C]

-40 40 60-20 0 20

25

15

20

10

2

4

6

3

35

30

R22

R410A


With regard to system technology, previ-ous experience with R22 can only be utilized to a limited extent. The distinctivetemperature glide requires a particulardesign of the main system components,e.g. evaporator, condenser, expansionvalve. In this context it must be consid-ered that heat exchangers should prefer-ably be laid out for counterflow operationand with optimized refrigerant distribution.There are also special requirements withregard to the adjustment of regulatingdevices and service handling.

Furthermore, the use in systems withflooded evaporators is not recommendedas this would result in a severe concentra-tion shift and layer formation in the evap-orator.

In addition to laboratory investigationsBITZER was also co-ordinating a com-prehensive program of field tests fromwhich the necessary operating experi-ence could be gained over a wide area.These tests have already demonstratedclearly that reliable compressor opera-tion depends entirely on the quality anddesign of the system.

BITZER can supply a range of semi-her-metic reciprocating, screw and scrollcompressors – including suitable oil – for R407C.

Converting existing R22 plants

A series of plants have been converted fortest purposes. Because of the abovementioned criteria, however, no generalguidelines can be defined. Each casemust therefore be examined individually.

In addition to R407C, there is a nearazeotropic blend being offered with theASHRAE designation R410A. It is used in real systems, mainly in air conditioningapplications.

An essential feature indicates nearly 50%higher cooling capacity (Fig.23) in com-parison to R22, but with the consequenceof a proportional rise in system pressure.

The research also indicates a favourableenergy consumption when used with lowcondensing temperatures and this givesgood premises for a low TEWI (GWP100 = 1720).

Just as advantageous are the high heattransfer coefficients (found in tests) in theevaporator and condenser, therefore pro-viding further potential for increased effi-ciencies. Because of the negligible tem-perature glide (< 0.2 K), the generalusability can be seen similar to a purerefrigerant.

The material compatibility is comparableto the previously discussed blends andthe same applies for the lubricants. How-

R410A as substitutefor R22

21


ever, the pressure levels and the higherspecific loads on the system componentsneed to be taken into account.


The fundamental criteria for HFC blendsalso apply to the system technology withR410A, however the extreme high pres-sure levels have to be considered (43°Ccondensing temperature already corre-sponds to 26 bar abs.).

At present the general availability of com-pressors and other system componentsfor this refrigerant has substantial limita-tions. Furthermore the resultant effect ofthe safety regulations are essential.

With the favourable properties of R410A,world wide research programs are under-way for the development and testing ofsuitable system components.

When considering to cover usual R22application ranges, the significant differ-ences in the thermodynamic properties(e.g. mass and volume flow, vapour densi-ty) must be evaluated. In addition, thehigh pressure levels of R410A may requiremajor design changes to the compressor,heat exchangers, controls, piping andhoses, together with special care for theoverall plant safety regulations affectingthe quality and dimensions of hoses andflexible elements (for condensing temper-atures of approx. 60°C and 40 bar!).

Another criterion is the relatively low criti-cal temperature of 73°C. Irrespective ofthe design of components on the highpressure side, the condensing temperatureis thus limited significantly.

BITZER has done comprehensive research with R410A and can offer specially designed compressors, inclu-sive of suitable oils, for testing purposes.

R419A (FX90) as a substitute for R22

The manufacturer (Atofina) offers this R22substitute for the conversion of existingR22 systems (preferably air conditioningplants) for which a “Zero ODP” solution isrequested. This refrigerant is also a mixtu-re with base components R125 andR134a with a higher portion of R125 anddimethylether (R-E170) as a third substan-ce instead of butane.

The good solubility of R-E170 in mineraland alkylbenzene oils provides a goodbasis for an operation with conventionallubricants as well. However, the criteria asdescribed for the two refrigerants in thechapter before have to be considered aswell. Similar circumstances can be app-lied to the thermodynamic properties withthe resulting consequences.

Since some time a further R22 substituteis offered on the market with the compo-sition components R125/R134a/R600. Itwas first introduced under the trade nameISCEON 59 (Rhodia) and in the meantimeis listed in the ASHRAE nomenclature asR417A.

Another blend variation with the samecomponents but with a different formula –trade name ISCEON 29 – was presentedat the beginning of 2003. In the frame-work of further development R600 will,however, be substituted by R600a infuture. According to the manufacturer’sstatement this refrigerant has been opti-mised for liquid chiller applications.

Like R407C, these are zeotropic blendsshow a significant temperature glide. Inthis respect the criteria described in connection with R407C are also valid.

Despite similar refrigeration capacity thereare fundamental differences in thermody-namic properties and in oil transportbehaviour. The high proportion of R125causes a higher mass flow than withR407C, a lower discharge gas tempera-ture and a relatively high superheatingenthalpy. These properties indicate thatthere could be differences in the optimiza-tion of system components and a heatexchanger between liquid and suctionlines might be of advantage.

Despite the predominant proportion ofHFC refrigerants the use of conventionallubricants is possible to some extentbecause of the good solubility propertiesof the R600(a) constituent. However, insystems with a high oil circulation rateand/or a large volume of liquid in thereceiver oil migration may result. In suchcases ester oil is recommended.

BITZER compressors are already provenwith R417A and are basically also suitable for ISCEON 29. An individualselection is possible upon demand.

R417A and ISCEON 29as substitutes for R22

The refrigerant NH3 has been used for morethan a century in industrial and larger refri-geration plants. It has no ozone depletionpotential and no direct global warmingpotential. The efficiency is at least as goodas with R22, in some areas even morefavourable; the contribution to the indirectglobal warming effect is therefore small. In addition it is incomparably low in price.Summarized, is this then an ideal refrige-rant and an optimum substitute for R22 oran alternative for HFCs!? NH3 has indeedvery positive features, which can also bemainly exploited in large refrigeration plants.

Unfortunately there are also negativeaspects, which restrict the wider use inthe commercial area or require costly andsometimes new technical developments.

A disadvantage with NH3 is the high isen-tropic exponent (NH3=1.31 / R22= 1.18 /R12=1.14), that results in a dischargetemperature which is even significantlyhigher than that of R22. Single stagecompression is therefore already subject tocertain restrictions below an evaporatingtemperature of around -10°C.

The question of suitable lubricants is alsonot satisfactorily solved for smaller plantsin some kinds of applications. The oils usedpreviously were not soluble with the refriger-ant. They must be separated with compli-cated technology and seriously limit theuse of “direct expansion evaporators” dueto the deterioration in the heat transfer.

Special demands are made on the thermalstability of the lubricants due to the highdischarge gas temperatures. This is espe-cially valid when automatic operation is considered where the oil should remainfor years in the circuit without losing anyof its stability.

NH3 has an extraordinarily high enthalpydifference and as a result a relativelysmall circulating mass flow (approximately13 to 15% compared to R22). This featurewhich is favourable for large plants makesthe regulation of the refrigerant injectionmore difficult with small capacities.

22

NH3 (Ammonia) as substitute for R22

A further criteria which must be consideredis the corrosive action on copper contain-ing materials; pipe lines must therefore be made in steel. Apart from this thedevelopment of motor windings resistantto NH3 is also hindered. Another difficultyarises from the electrical conductivity ofthe refrigerant with higher moisture content.

Additional characteristics include toxicityand flammability, which require specialsafety measures for the construction andoperation of such plants.

Resulting design and construction criteria

Based on the present “state of technolo-gy”, industrial NH3 systems demand total-ly different plant technology, compared tousual commercial systems.

Due to the insolubility with the lubricatingoil and the specific characteristics of therefrigerant, high efficiency oil separatorsand also flooded evaporators with gravityor pump circulation are usually employed.Because of the danger to the public andto the product to be cooled, the evapora-tor often cannot be installed directly atthe cold space. The heat transport mustthen take place with a secondary refrige-rant circuit.

Two stage compressors or screw com-pressors with generously sized oil coolers,must already be used at medium pressureratios, due to the unfavorable thermalbehaviour.

Refrigerant lines, heat exchangers and fit-tings must be made of steel; larger sizepipe lines are subject to examination by acertified inspector.

Corresponding safety measures and alsospecial machine rooms are requireddepending upon the size of the plant andthe refrigerant charge.

The refrigeration compressor is usually of“open” design, the drive motor is a sepa-rate component.

These measures significantly increase the expenditure involved for NH3 plants,especially in the medium and smallercapacity area.

Halogen free refrigerants

Efforts are therefore being made world-wide to develop simpler systems whichcan also be used in the commercial area.

A part of the research programs is dealingwith part soluble lubricants, with the aimof improving oil circulation in the system.Simplified methods for automatic return ofnon-soluble oils are also being examinedas an alternative.

BITZER is strongly involved in theseprojects and has a large number ofcompressors operating. The experien-ces up to now have revealed thatsystems with part soluble oils are diffi-cult to govern. The moisture content inthe system has an important influenceon the chemical stability of the circuitand the wear of the compressor. Besi-des, high refrigerant dilution in the oil(wet operation, insufficient oil tempera-ture) leads to strong wear on the bea-rings and other moving parts. This isdue to the enormous volume changewhen NH3 evaporates in the lubricatedareas.

These developments are being done ona widely used program. The emphasisis also on alternative solutions for non-soluble lubricants.

Besides to this various equipment manu-facturers have developed special evapo-rators, where the refrigerant charge canbe significantly reduced.

In addition to this there are also solutionsfor the “sealing” of NH3 plants. This dealswith compact liquid chillers (charge below50 kg), installed in a closed container andpartly with an integrated water reservoirto absorb NH3 in case of a leak. This typeof compact unit can be installed in areaswhich were previously reserved for plantswith halogen refrigerants due to the safetyrequirements.

It is still too early to give a final judgementconcerning the extended use of compactNH3 systems, in place of plants with HFCrefrigerants and mainly conventional tech-nology. From the purely technical viewpo-int and presupposing an acceptable price,it is anticipated that a wider range will beavailable soon.

23


Fig. 25 Comparison of discharge gas temperatures Fig. 26 NH3/R22 – Comparision of pressure levels

Dis

char

ge g

as t

emp

erat

ure

[˚C

]

Evaporation [˚C]

-40 10-20 040

60

140

100

80

tc

∆ tohη

40°C10K0,8

R290

R134a

R404A

-10-30

120R22

NH3

R723

160

180

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

2

4020

R22NH3

Conversion of existing plants

The refrigerant NH3 is not suitable for theconversion of existing (H)CFC plants; theymust be constructed completely new withall components.

The previously described experienceswith the use of NH3 in commercial refrige-ration plants with direct evaporation caused further experiments on the basisof NH3 under the addition of an oil solublerefrigerant component. The main goalswere an improvement of the oil transportcharacteristics and the heat transmissionwith conventional lubricants along with areduced discharge gas temperature forthe extended application range with singlestage compressors.

The result of this research project is arefrigerant blend of NH3 (60%) and dime-thyl ether “DME” (40%), developed by the“Institut fuer Luft- und Kaeltetechnik,Dresden”, Germany (ILK), that has beentested in a series of real systems. As alargely inorganic refrigerant it received thedesignation R723 due to it its averagemolecular weight of 23 kg/kmol in accor-dance to the standard refrigerant nomen-clature.

DME was selected as an additional com-ponent for its properties of good solubility

Supplementary BITZER informationconcerning the application of NH3(see also http://www.bitzer.de)

❏ Technical Information KT-640“Application of Ammonia (NH3)as an alternative refrigerant”

The production program from BITZERtoday includes an extensive selectionof optimized NH3 compressors forvarious types of lubricants:

❏ Single stage open reciprocatingcompressors (displacement 19 to152 m3/h with 1450 rpm) for air-con-ditioning, medium temperature anBooster applications

❏ Open screw compressors (displace-ment 84 to 250 m3/h – with paralleloperation to 1500 m3/h with 2900rpm) for air-conditioning, mediumand low temperature cooling.Options for low temperature cooling:– single stage operation– Economiser operation– Booster operation

R723 (NH3/DME) as analternative to NH3

24

R290 (Propane) as sub-stitute for R502 and R22

R290 (propane) can also be used as asubstitute refrigerant. As it is an organiccompound (hydrocarbon) it does not havean ozone depletion potential and a negli-gible direct global warming effect. To takeinto consideration however, is a certaincontribution to summer smog.

The pressure levels and the refrigerationcapacity are similar to R22/R502 and thetemperature behaviour is as favourable aswith R12 and R502.

There are no particular material problems.In contrast to NH3 copper materials arealso suitable, so that also semi-hermeticand hermetic compressors are possible.The mineral oils usually found in a CFCsystem can be used here as a lubricantover a wide application range.

Refrigeration plants with R290 have beenin operation world-wide for many years,mainly in the industrial area – it is a „pro-ven“ refrigerant.

Meanwhile R290 is also used in smallercompact systems with low refrigerantcharges like residential A/C units and heatpumps. Furthermore, a rising trend can beseen in its use with commercial refrigera-tion systems and chillers.

Propane is offered also as a mixture withIsobutane (R600a) or Ethan (R170). Thisshould obtain a good performance matchwith halocarbon refrigerants. Pure Isobu-tane is mostly intended as a substitute forR12 in small plants (preferably domesticrefrigerators).

The disadvantage of hydrocarbons is thelight flammability, and therefore beenclassified as refrigerants of “Safety GroupA3“. With the normal refrigerant chargefound in commercial plants this meansthat the system must be designed accord-ing to „flame-proof“ regulations.

The use of semi-hermetic compressors inso called „hermetically sealed“ systems isin this case subject to the regulations fordanger zone 2 (only seldom and shortterm risk). The demands for the safetytechnology include special devices


and high individual stability. It has a boi-ling point of -26°C, a relatively low adia-batic exponent, is non toxic and is availa-ble in a high technical standard of purity.In the given concentration NH3 and DMEform an azeotropic blend characterised bya slightly rising pressure level in compari-son to pure NH3. The boiling point lies at-36.5°C (NH3 -33.4°C), 26 bar (abs.) ofcondensing pressure corresponds to58.2°C (NH3 59.7°C).

The discharge gas temperature in air-con-ditioning and medium temperature rangesdecrease by about 10 to 25 K (Fig. 25)and thereby allows for an extension of theapplication range to higher pressureratios. On the basis of thermodynamiccalculations a single-digit percent rise incooling capacity results when comparedto NH3. The coefficient of performance issimilar and is even more favourable athigh pressure ratios, which experimentshave confirmed. Due to the lower tempe-rature level during compression an impro-ved volumetric and isentropic efficiency isalso to be expected, at least with recipro-cating compressors in case of an increa-sing pressure ratio.

Due to the higher molecular weight ofDME, mass flow and vapour density incre-ase with respect to NH3 by nearly 50%which is of little importance to commercialplants, especially in short circuits. In clas-sical industrial refrigeration plants, howe-ver, this is a substantial criterion withregard to pressure drops and refrigerantcirculation. Also from this standpoint itcan be clearly seen that in commercialapplications and especially in water chil-lers, R723 has its preferred utilisation.

The material compatibility is comparableto that of NH3. Although non-ferrousmetals (e.g. CuNi alloys, bronze, hard sol-ders) are potentially suitable, providedthat the water content in the system is ata minimum (<1000 ppm), a system designthat corresponds with typical ammoniapractise is recommended nonetheless.

As lubricant mineral oils or (preferred)poly-alpha olefin can be used. As mentio-ned before the portion of DME createsimproved oil solubility and a partial misci-bility. Besides this the relatively low liquid

density and an increased concentration ofDME in the circulating oil, positivelyinfluences the oil circulation. PAG oilswould be fully or partly miscible withR723 for typical applications but are notrecommended for reasons of the chemicalstability and high solubility in the com-pressor crankcase (strong vapour deve-lopment in the bearings).

Tests have shown that the heat transfercoefficient at evaporation and high heatflux is improved in systems with R723 andmineral oil than when using NH3 withmineral oil.

Further characteristics are toxicity andflammability. By means of the DME con-tent, the ignition point in air diminishesfrom 15 to 6% but, despite of this, theazeotrope still remains in the safety group B2.

Resulting layout criteria

The experiences made with the NH3 com-pact systems described above can beused in the plant technology. However,adjustments in the component layout arenecessary under consideration of the hig-her mass flow. Besides a suitable selec-tion of the evaporator and the expansionvalve a very stable superheat control mustbe ensured. Due to the improved oil solu-bility “wet operation” can have considera-ble negative results when compared toNH3 systems with non-soluble oil.

With regards to safety regulations thesame criteria apply to installation andoperation as in the case of NH3 plants.

Suitable compressors are special NH3versions which possibly have to be adap-ted to the mass flow conditions and to thecontinuous oil circulation. An oil separatoris usually not necessary with reciprocatingcompressors.

Bitzer NH3 reciprocating compressorsare suitable for R723 in principle. Anindividual selection of prototype com-pressors is possible on demand.

25


Fig. 27 R290/R1270/R22 – Comparison of performance data of a semi-hermetic compressor

Fig. 28 R290/R1270/R22 – comparison of pressure levels

Rel

atio

n R

290

and

R12

70 t

o R

22 (=

100%

)

Evaporation [˚C]

80

120

-40 0 10-30 -20 -10

90

110

100

Qo (R290)

COP (R1270)

COP (R290)

Qo (R1270)

tc 40˚Ctoh 20˚C

Pre

ssur

e [b

ar]

Temperature [˚C]

1

25

0 60

6

15

4

10

20

-40 -20

2

4020

R22

R1270

R290

to protect against excess pressures andspecial arrangements for the electricalsystem. In addition measures are requiredto ensure hazard free ventilation to effec-tively prevent a flammable gas mixtureoccurring in case of refrigerant leakage.

The design requirements are defined bystandards (e.g. EN378, Draft DIN 7003) andmay vary in different countries. For systemsapplied within the EU an assessment accor-ding to the EC Directive 76/117/EC (ATEX100a) may become necessary as well.

With open compressors this will possiblylead to a classification in zone 1. Zone 1demands, however, electrical equipmentin special flame-proof design.


Apart from the measures mentionedabove, propane plants require practicallyno special features in the medium and lowtemperature ranges compared with ausual (H)CFC and HFC system. When siz-ing components consideration shouldhowever be given to the relatively lowmass flow (approximately 55 to 60% com-pared to R22). An advantage in connec-tion with this is the possibility to greatlyreduce the refrigerant charge.

On the thermodynamic side an internalheat exchanger between the suction andliquid line is recommended as this willimprove the refrigeration capacity andCOP.

Due to the particularly good solubility withmineral oils, it may be necessary to usean oil with lower mixing characteristics orincreased viscosity for higher suctionpressures (air-conditioning range).

In connection to this, an internal heatexchanger is also an advantage as it leadsto higher oil temperatures thus to lowersolubility with the result of an improvedviscosity.

Due to the very favourable temperaturebehaviour (Fig. 25), single stage compres-sors can be used down to approximately -40°C evaporation temperature. R290could then also be considered as a directsubstitute for R502 or an alternative forsome of the HFC blends.

On demand a palette of semi-hermeticreciprocating compressors is availablefor R290. Due to the individual require-ments a specifically equipped compres-sor is offered. Extension “P“ with com-

pressor designation – e.g. 4CC-9.2PInquires and orders need a distinstiveindication to R290. The handling of theorder does include an individual agree-ment between the contract partners.Open reciprocating compressors arealso available for R290, together with acomprehensive program of flame-proofaccessories which may be required.

Conversion of existing CFC plants

Due to the flame-proof protection meas-ures required for an R290 plant, it wouldappear that a conversion of existing plantsis only possible in exceptional cases.

They are limited to systems, which can bemodified to meet the corresponding safe-ty regulations with an acceptable effort.

Supplementary BITZER informationconcerning the use of R290

❏ Technical Information KT-660“Application of Propane with semi-hermetic reciprocating compressors”

26

Carbon Dioxide R744 (CO2)as an alternative refrige-rant and secondary fluid


With regard to system technology, experi-ence gained from the use of propane canwidely be applied to propylene. However,component dimensions have to be altereddue to higher volumetric refrigerationcapacity (Fig. 27). The compressor dis-placement is correspondingly lower andtherefore also the suction and high pres-sure volume flows. Because of highervapour density the mass flow is almostthe same as for R290. As liquid density isnearly identical the same applies for theliquid volume in circulation.

As with R290 the use of an internal heatexchanger between suction and liquidlines is of advantage. However, due toR1270’s higher discharge gas temperaturerestrictions are partly necessary.

BITZER has carried out a series of investigations with R1270. In additionthere are experiences with the operationin real plants. An indivdual selection ispossible upon demand.

For some time there has also beenincreasing interest in using propylene(propene) as a substitute for R22/R502.Due to its higher volumetric refrigerationcapacity and lower boiling temperature(compared to R290) applications in medi-um and low temperature systems, e.g. liquid chillers for supermarkets, are ofparticular interest. On the other hand,higher pressure levels (>20%) and dis-charge gas temperatures have to be takeninto consideration, thus restricting thepossible application range.

Material compatibility is comparable withpropane, as is the choice of lubricants.

Propylene is also easily inflammable andbelongs to the A3 group of refrigerants.The same safety regulations are thereforeto be observed as with propane (page 23).

Due to the chemical double linkagepropylene is relatively reaction friendly,which means that there is a danger ofpolymerization at high pressure and tem-perature levels. Tests carried out byhydrocarbon manufacturers and stabilitytests in real applications show that reac-tivity in refrigeration systems is practicallynon-existent. Doubts have occasionallybeen mentioned in some literature regard-ing propylene’s possible carcinogeniceffects. These assumptions have beendisproved by appropriate studies.

Propylene (R1270) as analternative to Propane

CO2 has had a long tradition in the refrig-eration technology reaching far into the19th century. It has no ozone depletingpotential, a negligible direct global warm-ing potential (GWP = 1), is chemicallyinactive, non-flammable and not toxic inthe classical sense. However, comparedto HFCs the lower practical limit in air hasto be considered. For closed rooms this mayrequire special safety and monitoring systems.

CO2 is also low in cost and there is nonecessity for recovery and disposal. Inaddition, it has a very high volumetricrefrigeration capacity, which equates toapprox. 5-8 times more than R22 and NH3.

Above all, the safety relevant characteris-tics were an essential reason for the initialwidespread use. With the introduction ofthe “Safety Refrigerants”, CO2 becameless popular and since the fifties had near-ly disappeared.

The main reasons for that are its relativelyunfavourable thermodynamic characteris-tics for usual applications in refrigerationand air-conditioning.The discharge pres-sure with CO2 is extremely high and thecritical temperature at 31°C (74 bar) isvery low. Depending on the heat sourcetemperature at the high pressure sidetranscritical operations with pressuresbeyond 100 bar are required. Moreover,the energy efficiency is often lower com-pared to the classic vapour compressionprocess (with condensation), and there-fore the indirect global warming effect issuitably higher.

Nevertheless, under an ecological point ofview, a favourable balance (low TEWI) canemerge in applications with potentiallyhigh leakage rates. This is valid, e.g. invehicle air-conditioning, provided thatthere are no efficiency disadvantagescompared to recent technologies. Thoughextensive research and development isdone in this field, a generally acceptedtechnical and ecological assessmentdoes, however, not exist at present.



Abb. 29/1 R744(CO2) – Pressure-/Enthapy-Diagram

0 200100 300 400 500 6000

20

40

60

80

100

120

140

160

Enthalpy [kJ/kg]

Pre

ssur

e [b

ar]

31°C

2 Trans-critical process

Sub-critical process

R744 (CO )

Fig. 29/2 R744(CO2)/R22 – Comparison of pressure levels

Pre

ssur

e [b

ar]

Temperature [˚C]

1

70

0 60

6

40

4

30

50

-40 -20

2

4020

R744 (CO2)

R22

tKr

20

15

10


For the high temperature side of such acascade system, a compact cooling unitcan be used, whose evaporator serves onthe secondary side as the condenser forCO2. Chlorine-free refrigerants (NH3, HCsor HFCs) refrigerants are suitable.

With NH3 the cascade heat exchangershould be designed so that the dreadedbuild-up of ammonium carbonate is pre-vented in the case of leakage. This tech-nology has been applied in breweries fora long time.

A secondary circuit for larger plants withCO2 could be constructed utilising, to awide extent, the same principles for a lowpressure pump circulating system, as isoften used with NH3 plants. The essentialdifference exists therein, that the con-densing of the CO2 results in the cascadecooler, and the receiver tank (accumula-tor) only serves as a supply vessel.

The extremely high volumetric refrigera-tion capacity of CO2 (latent heat through

Further potential applications for example,for which the transcritical process caneven be of benefit, are heat pumps forsanitary hot water or drying processes.With the usually high temperature gradienton the high pressure side the temperatureglide can be used advantageously. Sani-tary water heat pumps are already beingmass-produced and are widely applied.

From energy and pressure level points ofview, much more beneficial applicationscan be seen for industrial and larger com-mercial refrigeration plants. For this, CO2can be used as a secondary fluid in acascade system and if required, in combi-nation with a further booster stage forlower evaporating temperatures (Fig. 30/1). The operating conditions are always sub-critical which guarantees good efficiencylevels. In the most favourable applicationrange (approx. -10 to -50°C), pressures are still on a level where already existingcomponents or items in development, e.g.for R410A, can be matched with accept-able effort.

the changing of phases) leads to very lowmass flow rates and makes it possible touse small cross sectional pipe and mini-mal energy needs for the circulatingpumps.

For the combination with a further com-pression stage, e.g. for low temperatures,there are different solutions.

Fig. 30/1 shows a variation with an addi-tional receiver where one or more Boostercompressors will pull down to the neces-sary evaporation pressure. Likewise, thedischarge gas is fed into the cascadecooler, condenses and then carried overto the receiver (MT). The feeding of thelow pressure receiver (LT) is achieved by alevel control device.Instead of classical pump circulation thebooster stage can also be built as a so-called LPR system. The circulation pump is thus not neces-sary but the number of evaporators isthen limited with a view to an even distri-bution of the injected CO2.

27

28

The compressors, for example, must beproperly designed because of the highvapour density and pressure levels (parti-cularly on the suction side). There are alsospecific requirements with regard to mate-rials. Furthermore only highly dehydratedCO2 must be used.

High demands are made on lubricants aswell. Conventional oils are mostly not mis-cible and therefore require costly meas-ures to return the oil from the system. Onthe other hand, a strong viscosity reduc-tion with the use of a miscible and highlysoluble POE must be considered.Besides, there is insufficient experience in general on the long term stability ofrecently developed lubricants.

Further development work is necessary,also with regard to the adaptation of tech-nical standards and safety requirements.

BITZER is actively involved in a numberof projects. For subcritical applicationsspecially designed compressors, inclu-sive of suitable oil, can be offered.

In the case of a system breakdown wherea high rise in pressure could occur, safetyvalves can vent the CO2 to the atmos-phere with the necessary precautions.

As an alternative to this CO2 absorbingstorage systems are used where longershut-off periods can be bridged without acritical pressure increase.

For systems in commercial applications adirect expansion version is possible aswell.

Supermarket plants with their usuallywidely branched pipe work offer an espe-cially good potential in this regard. Themedium temperature system is then car-ried out in a conventional design or with asecondary circuit and for low temperatureapplication combined with a CO2 cascadesystem (for sub-critical operation). Asystem example is shown in Fig. 30/2.

For a general application, however, not allrequirements can be met at the moment.It is worth considering that system tech-nology changes in many respects andspecially adjusted components are necessary to meet the demands.

Supplementary BITZER informationconcerning compressor selectionand the use of CO2

❏ Brochure KP-120:CO2 Compressors – Octagon K Series

❏ Paper: Semi-hermetic reciprocatingand screw compressors for CO2cascade systems


Fig. 30/2 Conventional refrigeration system combined with CO2 low temperature cascade

CO Cascade2

LT

HFC (NH3 / HC)*

MT

* only with secondary system

Simplifiedsketch

Fig. 30/1 Casacde system with CO2 for industrial applications

Simplifiedsketch

CO2

LT MT

LC

PC

CPR

MT LT

NH3 / HC /HFC

29

R124 and R142b as substitutes forR114 and R12B1

Instead of the refrigerants R114 andR12B1 predominately found in the past inhigh temperature heat pumps and cranecabin A/C installations, the HCFC R124and R142b can be used as alternatives innew installations.With these gases it is also possible to use long proven lubricants, preferablymineral oils and alkyl benzenes with high viscosity.

Because of the Ozone Depleting Potential,the use of these refrigerants must certain-ly only be regarded as an interim solution.The flammability of R142b should also beconsidered with the resulting safety impli-cations (refrigerant group A2).

Resulting design criteria/Converting existing plants

In comparison to R114 the boiling tem-peratures of the alternatives are lower(approx. -10°C) which results in larger dif-ferences in the pressure levels and refrig-eration volumetric capacities. This leadsto stronger limitations in the applicationrange concerning high evaporation andcondensing temperatures.A conversion of an existing installationwill in most cases necessitate theexchanging of the compressor and regu-lating devices. Owing to the lower volumeflow (higher volumetric refrigerationcapacity), possible adjustments to theevaporator and the suction line will be required.

Over the previous years BITZER com-pressors have been found to be wellsuited with R124 and R142b in actualinstallations. Depending on perform-ance data and compressor type modifi-cations are necessary, however. Perfor-mance data including further designinstructions are available on request.

Abb. 31 R13B1/HFC alternatives – Comparison of discharge gas temperatures of a 2-stage compressor

totc∆to

-70°C40°C20K

Basis R13B1

FX

80

R41

0A

ISC

EO

N 8

9

Dis

char

ge g

as t

emp

erat

ure

– re

lativ

e d

iffer

ence

to

R13

B1

[K]40

30

20

10

0

-10

-30

-20

Due to the limited markets for systemswith extra high and low temperature appli-cations, the requirements for the develop-ment of alternative refrigerants and sys-tem components for these areas has notbeen so great.

Only a few years ago a group of alterna-tives for the CFC R114 and Halon R12B1(high temperature), R13B1, R13 and R503(extra low temperature) were offered as thereplacements. With closer observations ithas been found that the thermodynamicproperties of the alternatives differ considerably from the substances useduntill now. This can cause costly changesespecially with the conversion of existingsystems.

Alternatives for R114 and R12B1

At present R227ea and R236fa are regard-ed as the prefered substitutes, however,the availability of R236fa is partly limited.

R227ea cannot be seen as a full replace-ment. Recent research and field testshave shown favourable results, but with

normal system technology the criticaltemperature of 102°C limits the condens-ing temperatures to about 85..90°C.

R236fa provides the more favourable con-ditions at least in this regard – the criticaltemperature is above 120°C. A disadvan-tage, however, is the smaller volumetricrefrigeration capacity. This is similar toR114 and with that 40% below the perfor-mance of R124 which is widely used forextra high temperature applications today.

Refrigerant R600a (Isobutane) will be aninteresting alternative where the safetyregulations allow the use of hydrocarbons(Group A3). With a critical temperature of135°C, condensing temperatures of 100°Cand more are within reach.

The volumetric refrigeration capacity isalmost identical to R124.

Alternatives for R13B1

Besides R410A, Forane FX80 (Atofina)and ISCEON 89 (Rhodia) can be regardedas potential R13B1 substitutes.WithR410A a substantially higher dischargegas temperature is to be considered whencompared to R13B1 which restricts theapplication range even in 2-stage com-pression systems to a greater extent.

Chlorine free substitutes for special applications


30


In addition to this, the steep fall of pres-sure limits the application at very lowtemperatures and may require a changeto a cascade system with for exampleR23 in the low temperature stage.

Lubrication and material compatibility areassessed as being similar to the otherHFC blends.

Alternatives for R13 and R503

The situation is more favourable withthese substances as R23 and R508A/R508B can already replace R13 and R503.Refrigerant R170 (Ethane) is also suitablewhen the safety regulations allow the useof hydrocarbons (Group A3).

Due to the partly steeper pressure curveof the alternative refrigerants and thehigher discharge gas temperature of R23compared with R13, differences in per-formance and application ranges for the

compressors must be considered. Individ-ual adaptation of the heat exchangers andcontrols is also necessary.

As lubricants for R23 and R508A/B, polyolester oils are suitable, but these must bematched for the special requirements atextreme low temperatures.

R170 has also good solubility with con-ventional oils, however an adaptation tothe temperature conditions will be neces-sary.

BITZER has already carried out investi-gations and also collected experienceswith several of the substitutes mentioned,performance data and instructions areavailable on request.Due to the individual system technologyfor these special installations, consul-tation with BITZER is necessary.

FX 80 is – like R410A – a mixture of R32and R125, with a higher proportion ofR125, however. Amongst other things, thisresults in a rise in vapour density andlower discharge gas temperature, whichcan be advantageous, depending on theapplication and the compressor design.

ISCEON 89 is a mixture of R125 and R218with a small proportion of R290. Due tothe properties of the two main compo-nents, density and mass flow are relativelyhigh and discharge gas temperature isvery low. Liquid subcooling is a particularadvantage.

All of the mentioned types have relativelyhigh pressure levels and are therefore lim-ited to 40 through 45°C condensing tem-perature. They also show less capacitythan R13B1 at evaporating temperaturesbelow -60°C.

According to EN 378-1, Annex E

N/A Data not yet available

32

Alternative refrigerant has larger deviation in refrigerating capacity and pressure

Alternative refrigerant has larger deviation below - 60°C evaporating temperature

These statements are valid subject to reservations; they are based on information published by various refrigerant manufacturers.

Also proposed as a component in R290/600a-Blends (direct alternative to R12)

Time horizont 100 years – according to IPCC II (1996) and published manufacturer’s data

Classification according to EN378-1 and ASHRAE 34

09.04

Fig. 32 Characteristics of alternatives (continued on Fig. 33)

3

4

5

61

2

Refrigerant Properties

0.050.020.06

0.030.0350.050.05

0

0.020.030.040.030.026

0

0

0

15004701800

9701060129012701770

22501960252035702650

130014028003800650

29006300

11700

32603300177022802530

1525195024002230

1725

2360

3090

1186011850

08333

3

1

R22R124R142b

R401AR401BR409AR409BR413A

R402A R402BR403AR403BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407AR407BR422A

R407CR417AR419AISCEON 29

R410A

FX80

ISCEON 89

R508AR508B

R717R723R600aR290R1270

R170

R744

Composition(Formula)

Substitute for

ODP

[R11=1.0]

GWP(100a)

[CO2=1.0]

Practicallimit

[kg/m3]

Safetygroup

Appplication range

5

HFCFC/HFC Service-Blends (Transitional Alternatives)

HFKW – chlorfreie – Kältemittel (langfristige Alternativen)

HFC – chlorine free – Blends (Long Term Alternatives)

Halogen free Refrigerants (Long Term Alternatives)

0.30.110.049

0.30.340.160.170.08

0.330.320.330.410.41

0.250.0270.390.0480.054

N/A0.59

0.68

0.480.520.330.350.5

0.310.15N/A0.35

0.44

N/A

N/A

0.230.2

0.00035N/A

0.0110.0080.008

0.008

0.07

A1A1A1

A1/A1A1/A1A1/A1A1/A1A1/A2

A1/A1A1/A1A1/A1A1/A1A1/A1

A1A2A1A2A2

A1A1

A1

A1/A1A1

A1/A1A1/A1A1/A1

A1/A1A1/A1A1/A2A1/A1

A1/A1

N/A

N/A

A1/A1A1/A1

B2B2A3A3A3

A3

A1

CHClF2CHClFCF3CCIF2CH3

R22/152a/124R22/152a/124R22/142b/124R22/142b/124R134a/218/600a

R22/125/290R22/125/290R22/218/290R22/218/290R22/143a/125

CF3CH2FCHF2CH3CF3CHF2CF3CH3CH2F2

CF3-CHF-CF3CF3-CH2-CF3

CHF3

R143a/125/134aR143a/125R32/125/134aR32/125/134aR125/134a/600a

R32/125/134aR125/134a/600R125/134a/R-E170R125/134a/600a

R32/125

R32/125

R125/218/290

R23/116R23/116

NH3NH3/R-E170C4H10C3H8C3H6

C2H6

CO2

R502 (R12 )

R114 , R12B1

R12 (R500)

R500R12 (R500)

R502

R13 (R503)

R503

R22 (R13B1 )

R13B1

R22

R502

R22 (R502)R22 (502)R114, R12B1R22 (R502)R22 (R502)

R13, R503

Diverse

R12B1, R114R114

R12 (R22 )mainly usedas partcomponentsfor blends

seepage 34

seepage 34

seepage 34

seepage 34

seepage 35

R13B1

Refrigerant type

HCFC-Refrigerants

3

4

5

6

1

1

1

1

1

2

2

2

Refrigerant Properties

33

Valid for single stage compressors

Data on request (operating conditionsmust be given)

Triple point at 5,27 bar

Stated performance data are average valuesbased on calorimeter tests

Rounded values

Total glide from bubble to dew line – based on 1 bar (abs.) pressure.Real glide dependent on operatingconditions.Approx. values in evaporator:H/M 70%; L 60% of total glide

Reference refrigerant for these values is stated in Fig. 32 under the nomina-tion “Substitute for” (column 3)Letter within brackets indicates opera-ting conditionsH High temp (+7/55°C)M Medium temp (-10/40°C)L Low temp (-35/40°C)

09.04

Fig. 33 Characteristics of CFC alternatives

3 4

5

6

1

2

R22R124R142b

R401AR401BR409AR409BR413A

R402A R402BR403AR403BR408A

R134aR152aR125R143aR32

R227eaR236fa

R23

R404AR507A R407AR407BR422A

R407CR417AR419AISCEON 29

R410A

FX80

ISCEON 89

R508AR508B

R717R723R600aR290R1270

R170

R744

HFCFC/HFC Service-Blends (Transitional Alternatives)

HFC – chlorine free – Refrigerants (Long Term Alternatives)

HFC – chlorine free – Blends (Long Term Alternatives)

Halogen free Refrigerants (Long Term Alternatives)

Refrigeranttype

HCFC-Refrigerants

3

6

Boilingtemperature

[°C]

Temperatureglide[K]

Criticaltemperature

[°C]

Cond. temp.at 26 bar(abs) [°C]

Refr.capacity

[%]

C.O.P

[%]

Dischargegas temp.

[K]

Lubricant(compressor)

1 2 1 1 3 3

88

1009899100100

1009899100100

103N/AN/AN/AN/A

98989698

95

95

105106N/A102101

-41-11-10

-33-35-34-35-35

-49-47-50-51-44

-26-24-48-48-52

-16-1

-82

-47-47-46-48-49

-44-43-43-45

-51

-51

-55

-86-88

-33-37-12-42-48

-89

-57

000

6.46.08.17.26.9

2.02.32.41.20.6

00000

00

0

0.70

6.64.42.5

7.45.6 6.64.5

<0.2

<0.2

4.0

00

00000

0

0

96122137

108106107105101

7583939083

101113667378

102>120

26

7371837672

87907981

72

70

70

1314

1331311359792

32

31

63105110

8077757376

5356575458

8085515642

96117

1

5554565356

58686462

43

44

50

-3-3

60581147061

3

-11

80 (L)

107 (M)108 (L)

109 (M)100 (M)105 (M)

109 (L)99 (L)

105 (L)112 (L)98 (L)

97 (M)N/AN/AN/AN/A

99 (L)102 (L)78 (L)93 (L)

100 (H)97 (H)

142 (7/40°C)

100 (M)105 (M)

N/A 89 (M)

112 (M)

+35

+13+18+7+6-9

~0+16+17~0+10

-8N/AN/AN/AN/A

-9-10+11-2

-8-25

-6

+60+35N/A-25-20

seepage 35

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5 5 5

5 5 5

5 5 5

4 4 4

5

5 5 5

-100-80-60-40-2002040

R124 ● R142b

R401A ● R409A ● R409B*

R401B

R413A

R22

R402B ● R403A

R402A ● R403B ● R408A

* R500-alternative Evaporation °CApplication with limitations

2-stage

2-stage

R404A ● R507 ● R407B

-100-80-60-40-2002040

R227ea ● R236fa

R134a

R407A

R407C ● R417AISCEON 29 ● R419A

R410A

ISCEON 89 ● FX80

R23 ● R508A ● R508B

Evaporation °CNew compressor generation

Condsensing temperature limited

Application withlimitations

For evaporating temperature below < -50°C pleaseconsult the refrigerant supplier

CASCADE

2-stage

2-stage

2-stage

2-stage

R404A ● R507AR407B ● R422A

1

2

3

3

1

2

2

2

34

Transitional/Service refrigerants

Fig. 34 Application ranges for HCFC’s and Service Blends

Chlorine free HFC refrigerants and blends

Fig. 35 Application ranges for HFC refrigerants and blends (ODP=O)

Application Ranges

R290 ● R1270

-100-80-60-40-2002040

R600a

R290/600a

R170

Evaporation °C

CO2

Application with limitations

CASCADE

2-stage

– see page 27/28 –

2-stage

2-stage

* see information on page 23/24

3NHR723*

(H)CFC

NH ● R7233

Service blends

HFC + blends

Hydrocarbons

Traditional oils New lubricants

VG VG VG

+VG

+VG

Min

eral

oil

(MO

)

Alk

yl-

ben

zene

(AB

)

Min

eral

oil

+ a

lkyl

-b

enze

ne

Pol

y-al

pha

-ol

efin

(PA

O)

VG

Especially critical with moisture

Possible higher basic viscotsity

Good suitability

Application with limitations

Not suitable

T

Extended test programT

Further information see pages 9/10 and explanations for the particular refrigerants.

Pol

yol

este

r (P

OE

)

Pol

yvin

yl-

ethe

r(P

VE

)

Pol

y-gl

ycol

(PA

G)

Hyd

rotr

eate

dm

iner

al o

il

VG VG

Application Ranges ■ Lubricants

35


Fig. 36 Application ranges for halogen free refrigerants

Lubricants

Fig. 37 Lubricants for compressors

Änd

erun

gen

vorb

ehal

ten

/ S

ubje

ct t

o ch

ange

/ T

oute

s m

odifi

catio

ns r

ésér

vées

09.

04

Bitzer Kühlmaschinenbau GmbHEschenbrünnlestraße 15

71065 Sindelfingen (Germany)Tel. +49(0)7031-932-0

Fax +49(0)7031-932-146 & [email protected] • http://www.bitzer.de

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