Stanbouly, S.

Wesolowski, A.

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Refrigeration and Air ConditioningConference School of Mechanical Engineering1996Serviceability Issues Associated with R407CRefrigerantS. StanboulyYork International CompanyA. WesolowskiYork International CompanyFollow this and additional works at: http://docs.lib.purdue.edu/iraccThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlStanbouly, S. and Wesolowski, A., "Serviceability Issues Associated with R407C Refrigerant" (1996). International Refrigeration and AirConditioning Conference. Paper 312.http://docs.lib.purdue.edu/iracc/312Abstract SERVICEABilllY ISSUES ASSOCIATED WITH R407C REFRIGERANT Souhel Stanbouly • Manager, Andrzej Wesolowski · Product Engineer Advanced Technologies York International Company Unitary Product Group Norman, Oklahoma Many investigators in the past have indicated that R407C is a drop· in HCFC-22 replacemem. Engineering testing have shown that R407C is not practically a simple drop- in refrigerant. System performance at ARI conditions of 80F Tdb/67F Twb indoor and 95F Tdb outdoor temperatures, has dmpped by 3% to 4% in capacity and up to 5% in efficiency. Additional testing was conducted to simulate slow leak (isothermal leak) from the system up to 50'ft of the nominal charge at the suction. discharge and liquid lines, and after TXV. When the leak simulation was completed the system was recharged with the nominal composition of R407C. Laboratory test results showed that the composition ofR407C changed especially during the first two leak simulations and were dependent on the location of the leak. Performance degradation of the system during the standard operation as wei! as during the leak simulation suggest that R407C is not a practically drop-in HCFC-22 replacement. I. Introduction The depletion of the Earth's stratospheric ozone layer is a global problem which has to be solved during the nexr several years. According w the Montreal Protocol and the Copenhagen Amendment, the phase-out of ozone depleting substances is as follows: CFCs in 1995- 100% HCFCs in 1996 - freeze in 2004-35% in 2010-65% in 2020- 99.5% in 2030- 100% The latest satellite measurement of the ozone layer over Antarctica revealed a hole as big as the United States which appears each Spring and grows even bigger every year. This situation puts pressure on scientists and engineers to find new fluids which would replace CFC and HCFC refrigerants. So far, chemical companies have manufactured few single refrigerants and mixtures which due to their Global Warming Potential (GWP) and Atmospheric Life Time (ALT), are rather short term replacements for CFCs and HCFCs. Hydrofluorocarbons (HFCs) have to fulfill very strict conditions, and must be both non-toxic and non-flammable. In addition, these refrigerants must e;UJibit low electrical conductivity, material and oil cumpatibiliry, good thermodynamic and transport properties. They must be chemically stable with G\VP of less then 0.5 and ALT ofless then 15 years. Finally, new refrigerants have to be cost effective and easy to manufacture. When the impact of CFCs and HCFCs compounds on rhe aunosphere was discovered, scientists, chemical companies, and the HV AC&R industry spent a great deal of money, time, a'ld energy to approve new alternate refrigerants. Alternatives have been sought among partially halogenated hydrocarbons, among different classes of organic compounds, and among mixtures. The 125 existence of hundreds of refrigerants is predicted. Of those only some 30- -+0 have been r:::ported as possible alternatives to CFCs and HCFCs. In the past. the most widely used refrigerants were CFC-11, CFC-12. HCFC-22, and R-502. However, since these refrigerants are no longer environmentally acceptable. we must continue to look for better alternatives. 2. Compressor Calorimeter Test The drop- in compressor :::alorimeter test was provided by the compressor manufacturer. The purpose of this test was to understand how the mixture performs with the compressor and ro quickly estimate the system performance. Also, the compressor calo~:imeter test <esults would allow to check the heat balance during the system tests. The testing of zeotropic mixtures provides particular challenges. Special consideration must be given to the terms "evaporating temperature" and "condensing temperature" since blends with temper::!tu<e glide may have significant temperature differences across the heat exchanger. Another concen while testing zeorropic blends wns that the refrigeration composition flowing through the compressor might be difr'e<ent than the bulk refrigero.nt composition in the system. This is due to different vapor :;xessures v>ithin the componems and t:-te possibility that one or more of tho: components could reside in the accumubror in the liquid phase or with the oil in the compressor crankcase. 3. Drop -in test The purpose of this test ;vas ro quickly estimate the performance of the system charged with R407C and to focus the attention on how the new refrigerant impactS performance a~d scn-iccability. This test w~ classified as a drop- in rest even though the lubricant and the TXV were changed. 3.1 Test facility The experimental evaluation of R407C system was conducted on a commercially available 3 ton HCFC-22 Split System Hear Pump (SSHP). The tested unit was instrumented with refrigerant-side and air-side temperature ar1d pressure sensors. wan transducers and watt hour meter. Temperarures were measured with thennocouples. Pressure readings were made with pressure transducers. Indoor and outdoor conditions were maintained within 0.5F dry-bulb, and within I% relative humidity of the set conditions. All instrumentation were calibrated before conducting the test. The test was perfonned according to the ARI Standard 210/240 (1989) following the loop air~enthalpy method. The enthalpies were determined by measuring the wet and dry bulb temperatures along with the pressure of the air entering and leaving the indoor unit. The 3 ton SSHP was placed in the psychrometric room simulating outdoor conditions (outdoor unit), while the indoor unit was located in another psychrometric room simu-lating indoor conditions. 3.2 Tested equipment A 3 ton HCFC-22 split heat pump - Capacity: 3 ton - Efficiency: 12 SEER was tested with the following changes: - Compressor: POE oil -Expansion device: TXVs (ID and OD) were adjusted ~Refrigerant: R407C - No other changes were made to the system 126 3.3 Test results • performance The compressor, TXV, oil and refrigerant were changed. The system was flushed three ( 3 ) times to insure l<:ss than 5% of mineral oil (~10) remained ia the system. Therefore. the test represent pure drop · in repbcement of HCFC~22 which is realized in the field. The drop- in performance test results obtained during the steady-state cooling aad he:J.ting conditions with the working fluids HCFC~22 and R-+07C ~e p~esented j;-, Fig.! and Fig.2. ~ ~ "' ~ 96 0: ;: "' w w > 93 >= < 92 ..J "' 0: 91 so DOE' A' TEST RESULTS HCFC-22 vs R407C Fig.1 TEST RESULTS HCFC-22 vs R407C Fig.2 i!SlHCFC-22, •I<lR407C The comparison of R407C test with HCFC-22 baseline test showed that the capacity and EER measured with the blend R407C were 3% to 4% lower for the cooling mode. For the heating mode, the capacity was 4% to 9.0% higher and EER was 3% to 4.0% lower than that of HCFC-22. The efficiency degradation was due to the higher pressure ratio of R407C. On the other hand, the lower capacity was due to higher vapor specific volume of the R407C mixture so the compressor with the fixed displacement pumped Jess refrigerant through the system. Related to the performance is a temperature glide and the heat exchanger geometry which could be related to the degradation in performance of the system. The temperature glide could be beneficial if the heat exchanger is configured as counter flow. 127 -leakage The objectives of the leakage test was to simulate serviceability of the unit and to determine the effect of repeated loss of the system charge and recharge on the system performance. This issue is vital in case of field units '.vhich are topped off with charge several times by lleld technician. The system performance as well as circulating and leaked mixture composition, are cmci<ll. It was desired to determine the percent system performance degrad<ltion, as well as the final circul<llion composition. The final (circulating and leaked) mixture composition is a concern not only due to performance, but flammability issue <lS welL (Due to lack of proper equipmem- gas chromatograph - for the composition analysis w<: con~emruted on the system performance degmdation). The leakage test was simulated by removing a known amount of charge from the system and recharging the same amount of pure mixture (R407C). The leakage was conducted in four (4) different places: - afterTXV - suction lin.:: at 6" from the compressor - discharge line at 6 .. from the cone pressor - liquid lii1e at the exit from the coil denser To simulate a leak the following procedure was us.::d: -from each location; 10% of the system nameplate charge was removed - system was charged to nameplme amoum - coolii'lg and heating ARI tests were conducted -the removal and recharge for 20'7c, 30'7c. 40%, and 50% of the system nameplate charge were repeatd. 4. Results analysis Shown on the following charts are the test results from the leakage tests. During these tests, there was a considerable fluctuation in latent heat, subcooling, and superheating measurement Therefore, for a comparison of the system performance in each test the results were normalized, which gives a good representation of the overall system performance. The test results are presented in Fig. 3 through Fig. 10. 4.1 Capacity and Efficiency The results obtained during the steady state cooling and heating modes are shown in Fig. 3, 4, 5, and 6. The cooling and heating capacity dropped by 3% to 4% when the lea'< was simulated after TXV. This was due to the 2 phase flow and the loss of R32 which is the highest pressure component in the mixture. 4.2 Subcooling and Superheating The maximum subcooling change was measured when leak occurred in the liquid line during the cooling mode as indicated in Fig.8. In terms of superheating the greatest decrease was observed during the leak from the suction line in the heating mode. It was due to the loss of R32 and Rl25 from the system. 5. Discussion The general observed trend was a drop in both capacity and efficiency and also in suction and discharge pressures. It was due to a loss ofR32 which is the highest pressure component in the mixture. Flammability issue may have to be considered for vapor leaks due to the higher percentage of R32 in the leaking vapor. Pressures drop causes a drop in the power consumption by the compressor. 128 The system performance was slightly effected by shifting the composition in the system. Capacity for cooling and heating modes dropped approximately 3% to 4%, and efriciency dropped by 5% in the worse case. 6. Conclusion A typical Split System Heat Pump (SSHP) was tested with alternative refrigcr::mt. Without any changes (drop-in test) rhe R407C mixture showed decreases in efficiency and capacity. The mixtur.:: has a m:1jor oroblem- fractionation. due w the temperature glide. The basic issue is how tO deal with the difference in ;he composition between the liquid and vapor ph:1se. Due lO the fracdonation issue and the performance degradation the R407C mixture cannot be classified as a drop- in repln.cement for HCFC-22. The most important part of the test was how a mixlllr<:: with the temperature glide beha v,;: in th<: field. and how to deal in the field with this kind of mixture. \Vhen a leak occurs the technician cha;;ge the system based on the superheat!subcooling. becau:;e he can measure temperatures and pressures. Depends on the location of the leak the system during the recharge process can be over- or under-chc.rge. Overch:!rging the system decreases the system efficie<1cy and in addition when the mixture leaked from th<: two phase flow area the rem:1ined mixture contains more R! 25 ar<d R i 3C:.a. :\fore R 125 in the system increase in addition the power consumption of the system. Undercharging the system (le2.k occurs at the suction line) decrease the capacity of the systtm a:; weli the suction and discharge pressures. This is due tO the loss of R32 which is the highest pressure componc:nt of the mixture. Summarize the test results we concluded: 1. Superheat and subcooling variation: a) The subcooling and superheat varied depending on the leak location b) Cooling superheat variation: - rhe leak from rhe liquid line decreased rhe superheat due to a less R32 and R!25 in rhe system -the leak after rhe TXV increased the superheat due to a lower percentage of R32 in the system c) Cooling subcoolint variation: - rhe leak from the liquid line ~:kcreased the subcooiing due to a less of R32 and Ri25 in rhe system -the leak from the suction line increased the subcooling due to the higher amount of R I34a in rhe system d) Heating superheat variation: - loss of R32 and R 125 from the system during the leak after rhe TX\' decreased the superheat e) Heating subcooling variation: - the leak from the liquid line decreased the subcooling due to the lower R32 concentration in the system -the leak from the discharge line increased rhe subcooling due to the higher Rl34a concentration in the system. 2.Perfonnancevariation a) \Vhen 50% of charge was leaked and recharged to the nameplate amount, the capacity dropped 3% - 4% and efficiency 5% b) Capacity and efficiency degradation: - capacity and efficiency depend on the location of rhe leak - the highest degradation in both capacity and efficiency from the suction line and after the TXV is due to rhe two phase flow when leaked vapor was richer in R32 c) Higher amount ofHFC-125 in the system decreased the efficiency d) The composition change has a significant impact on the subcooling and superheating during both cooling and heating modes. 129 B~sid~s the performJ.IlC-.! dcgrad..2.t!o~ :::m. z:eorrop1c ~: xrurc creo.t~.s another proble-r:1s rel~teC :0 :h~ temperature glide and fractionation :J.Ssociated with the :emperature glide:. Th<:se problems"~~~ i.;<>nti:1-::C: and are as follows: 1. Servic<': issues: 2.) The composition or refrigerant rem:lining in the system that is ka.king cannot easily d<:termine b) Th<: system must be :;harged 1.\ ith the liqu!o ;:'has~ c) The com;:JOsition of ref6gerant in ch<Uging cylinder cannOt c:annct t:asily determine d) If a system leak o.::cufS. the system should be rc:claimed a;:Jd recharg~d with the nan~.::;:<..\tc :OIT'.C't.:r.t e) Due ro superheat and subcoc,lir.g v..l:i..ltions. a t<:chnicio.n can easily overcho.rge th<: s; stem if he charges to superheat f) The HCFC-22 system has to be tlushed before charging with R.107C and POE oil g) POE oil is very hygroscopi:: and the systan c;::mnot b<: open<:d !onge; than 10-15 min. h) ~!ixrure of \.Vilter and POE oil form :J.cid t:har. reJ.ct \VHh mo~or winding insul.:::ttion D :E'OE oil ac~ as d~t~rgent. rcn10\ :::g p;1r:J.ffln. used ~ls;:,. drO.\\.ing lubrjcant that subscqu~nLl; :.:~11 ?;:;g co.pill:lry tubes k) :-;ew leak det:::ction equipmem i; ;equi~ed 1) Recove:y machine i; requi~ed ~. Design issues a) Temperature glide etTecr" coii~ rc:cl~stg:-1 :s r~quired to :3.K~ rhc ~Jv:1nrag~ of rhe glid~ b) Additional surface 3;e2. 'vii! b::: n<:eded co meet min:mum ::;-::::~gy ;-:ffi.:i~;-:cy r.::quircm::nts c) Op~imizing inner groov~ geomer:-y ot· ~nhnn:.:cd tubes ro prop<:ni~s of nC\.\ r~t-rigcr:ln! could 0~ :-equ:rcd d) The compressor bearing lubricationS) stems can be ~:::designed e) Higher discharge temperature and low.er heat transfer chura.:tenstks rcqui~e red.::signed OD anc ID .:oils f) Tr:e use of the z.eotropic mi,,auro: may ~esult in an ice formation i>1 the low temperawre 3. M:mufacturing issues: J) ).!!ixture composition in the storJ.ge tank and the charging statioil can vo.ry b) In ca.>e that in a storage tank left :20% of R..+07C, all remained mixture should be reclaimed? c) Gas chromatography can be required on the production line d) New leak detection equipment is required e) Lower moisture level (bellow 60 ppm) is required f) POE oil could potentially react with expending lubricants, rust inhibitors, solvents, and other chemicals g) Productio~ process changes are nec~ssary to prevent moisture contamination 4. Safety issues: a) Due to the temperature glide the mixture fractionate b) Leaking gas can be flammable (rich in R32) c) ~1ixrure of water and POE oil forms acid, therefore eyes and hand pwte::tion is required during &.::: servrce ACKNOWLEDGMENTS The authors would like to acknowledge the support of York International- Unitary Product Group in Norman and the cooperation of Rick Marra!e- Vice President of Engineering, we are greatly appreciated. 130 '§ §. ,.. u ~ < '-' 101 99 R~07C ·COOLING CAPACITY VARIATION AS A FUNCTION OF% REFRIGERANT REMOVAL AND ADDITION I i ........--orsch i.re I --a--wc;.Irr~ I ......__.. - -· - -· - -· - - - -· - .. -.-A:-t~r-;-xv : ~'4--- ' ::t: ' ' . ... Suc.~;:--e -.. -- -97 . 0 102 10 20 30 % MIXTURE REMOVeD Fig.3 40 50 R407C ·COOLING Ei:R VARIATION AS A FUNCTION OF'(, REFRIGi:RANT REMOVAL AND ADDITION 1 --+--Crsc."l.lrr~ - -o - ... _ .. • ___ ·• --4--L!q. 1rr.; ~~-.:; --A-AMe~D:V 100~ :: i ~ --:::' - ~-•·scc,.ce 94 ' 2C 30 sc ~~ \1IXTURE rt~~.10'JEO F!g.4 R407C ·HEATING CAPACITY VARIATION AS A FUNCTION OF% REFRIGERANT REMOVAL AND ADDITION 002 --------------------------------------'2 I '§ ~ 1C~,...~~---.. -:-.. -.------:--.-. :----! 0 ssj -..._ i ;t ----~ -s. 5 ! 95~----------------------------------~ '% MIXiURE ~EMOV~D Fig.5 50 __,__ Disdi.Jrn12 ------Llc.lir.e -.l-AJ:er-:J:V • 4- suc.lir.~ R407C ·HEATING COP VARIATION AS A FUNCTION OF% REFRIGERANT REMOVAL AND ADDITION 0 10 20 30 %MIXTURE REMOVED Fig.S 131 40 50 -+--Disd'Uir:e ·-----LiG.line : :....._..,-AfterTXV, : • • • Scc.:ine 1 R407C- COOLING SUPERHEAT VARIATION AS A FUNCTION OF %REMOVAL AND ADDITION ,; -----------------------------------+--- r;,sc!i.itne --D--L.(;.~::'Ie --6- A.~er TX.V - .. - s .... n::.!t:-:~ % MIXTURE REMOVED Fig.7 R407C- COOLING SUB COOLING VARIATION AS A FUNCTION Or ,,_MIXTURE REMOVAL AND ADDITION 15 -----------------------------------------1.3 . .. 8' ... - ........... - ....,. -----e---- .... ' ·~ < ~-------... ,..__---!:r __ ..,i, I .,..__ -i : l . J 2C -" 50 .. ,, ~.J11XTURE REMOV~D Fig.s ..........,._.CtS.:~-~r~ ----11-- -iqJ na --A- Att~r 7"'.1..'1 - • .. Such··~ R407C- HEATING SUPERHEAT VARIATION AS A FUNCTION OF %REFRIGERANT REMOVAL AND ADDITION 20 :;,:; % MiXTUR:: REMDV:OD Fig.9 50 ,.........,._.c,sc...., ·!"'~ i__.,__LiqJir.~ -...-~~erTXV '"' • • St.:c..inc R407C- HEATING SUBCOOLING VAP.I.e.TION AS A FUNCTION OF% REFRIGERANT REMOVAL AND ADDITION 10 20 so % MIXT1JRE REMOVED Fig.10 132 40 50 ·-CJ~.Ime. ,_..,__l.iqJine I . ) --.-Attar iXV i ·-•-s~~e, 

Serviceability Issues Associated with R407C Refrigerant

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Serviceability Issues Associated with R407C Refrigerant

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