Joachim Gerstel - DuPont - NUOVI REFRIGERANTI A BASSO GWP ALTERNATIVI ALL’R-404A NELLA REFRIGERAZIONE COMMERCIALE
Testing of Low GWP R-404AAlternatives in CommercialRefrigeration SystemsBarbara H. Minor & Joachim GerstelDuPont FluorochemicalsMilano, 7th-8th June 2013
Topics Regulatory Environment Properties of New Refrigerants Thermodynamic Cycle Performance Drop-in System TestingReach-in FreezerDisplay Case/Condensing Unit Summary2
Growing regulatory pressure on HFCs EU – F-Gas directive has GWP cap of 150 in new vehiclemodel a/c systems beginning January 1, 2011; HFC-134a nolonger allowed EU – EU Commission proposed revisions to F-Gas regulationregarding stationary requirements Australia – Instituted carbon tax starting July, 2012 Global – Potential for HFC phase-down under the MontrealProtocol framework (cap and allocation) R-404A is a leading target for replacement as it has one ofthe highest GWPs for HFCs (100 yr 3922 - AR4)
New low GWP Alternatives for R-404A DR-7 2L Mildly Flammable GWP = 246 HFC-32/HFO-1234yf at 36/64 wt% 94% lower GWP than R-404A Suitable for smaller charge R-404A systems due to chargesize restrictions in EU codes and standards DR-33 Nonflammable GWP = 1410 32/125/134a/1234yf at 24/25/26/25 wt% 65% lower GWP than R-404A For all R-404A systems, including larger systems ifnonflammability is required Potential for retrofit of existing R-404A systems
Refrigerant PropertiesR-404A DR-7 DR-33100 yr GWP 3922 246 1410Flammability None 2L NoneBoiling Point °C -47 -48 -46Critical Point °C 72 81 82Vapor Pressure at25°C in kPa1254 1372 1271Liquid Density at25°C in kg/m³1044 1133 1139Vapor Density at25°C in kg/m³65,3 46,8 48,9
Evaporator temperature = -26ºC, Condenser temperature = 43ºC,Subcool amount = 14K, Suction temperature = -4ºC,Compressor isentropic efficiency = 75%.SuctPresskPaDischPresskPaCompRatioCompressDischTemp °CAverageTempGlide KCapRel to404ACOPRel to404AR-404A 242 1969 8,1 86 0,4 100% 100%DR-7 230 1987 8,6 107 5,7 103% 101%DR-33 207 1869 9,0 103 4,3 95% 102%Thermodynamic Cycle PerformanceDR-7 and DR-33 have comparable capacity andenergy efficiency compared to R-404A
System Testing – Two Door Reach-in Freezer- 1,5 m³ double-door unit designed for R-404A- Reciprocating two piston compressor- Refrigerant charge size 1,15 kg,adjusted based on liquid density- Polyol ester (POE) 32 centistokeslubricant-Tested per AHAM Standard HRF-1-2008-Tested at three ambient temps: 32ºC,24ºC and 21ºC- Average freezer compartment tempcontrolled at -17ºC, average evaporatortemp -28ºC
Reach-In Freezer Schematic- no equipment changes for candidate testing, except TXV closed one turn
Reach-In Freezer Test ResultsEnergyConsRel toR-404AMassFlowRate(kg/h)SuctPress(kPa)DischPress(kPa)CompRatioComp DischTemp (ºC)Ambient t = 32ºCR-404A 100% 44 211 2027 10 90DR-7 92% 34 191 2133 11 105DR-33 96% 30 172 1931 11 104Ambient t = 24ºCR-404A 100% 46 198 1647 8 75DR-7 95% 35 184 1728 9 91DR-33 100% 31 172 1551 9 88Ambient t = 21ºCR-404A 100% 48 199 1558 8 70DR-7 97% 36 179 1600 9 85DR-33 100% 33 172 1448 8 83 equivalent to slightly reduced energy consumption comparable pressures and compression ratio modest increase in discharge t and lower mass flow rate
System Testing – Display Case with External Condensing Unit 2,5 m open food display case designedfor R-404A, fully loaded with foodsimulator Reciprocating compressor with POE 32oil Refrigerant charge size ~3,8 kg,adjusted based on liquid density Tested per ASHRAE Standard 72-2005 Tested at two ambient temps: 28ºC and35ºC in outdoor room, 24ºC in indoorroom Only minor TXV adjustment made (1,6turns closed) Tested at low and medium tempconditionsOpen Display Case in Indoor RoomCondensing Unit in Outdoor Room
CONDENSING UNIT AND DISPLAY CASE LAYOUTOUTDOOR ROOM INDOOR ROOMEvapPressureRegulatorT, P =TEMP.ANDPRESSTAPSSuction LineLiquid LineInsulatedSuction-LiquidHeat ExchangeENVIRONMENTALCHAMBERMass FlowTo Discharge LinePTPsPT T TPTFrozen Food CaseCondensing UnitT TsPd TdkW28ºC or 35ºC 24ºC
Condensing Unit/Display Case Low Temp ResultsEnergyConsRel toR404AMassFlowRatekg/hSuctPresskPaDischPresskPaCompRatioAvgFoodTempºCCompDischTempºCAmbientt = 28ºCR-404A 100% 32 112 1438 13 -17 78DR-33 97% 26 104 1407 14 -17 83Ambientt = 35ºCR-404A 100% 33 127 1722 14 -16 87DR-33 96% 26 115 1685 15 -15 92 ~3% lower energy consumption Similar pressures and compression ratio Modest increase in discharge t and slightly lower mass flow rate
Condensing Unit/Display Case Med Temp ResultsEnergyConsRel toR404AMassFlowRatekg/hSuctPresskPaDischPresskPaCompRatioAvgFoodTempºCCompDischTempºCAmbientt = 28ºCR-404A 100% 38 262 1544 5,9 2,2 72DR-33 92% 32 262 1496 5,7 2,2 75Ambientt = 35ºCR-404A 100% 41 248 1827 7,4 2,2 82DR-33 88% 34 283 1792 6,3 2,8 84 8-12% lower energy consumption Similar pressures and compression ratio Less increase in discharge t and slightly lower mass flow rate
Summary New low GWP refrigerants for R-404A under development DR-7 has a GWP of 246, is mildly flammable (2L) and suitablefor single condensing unit systems, stand-alone coolers andfreezers. DR-33 has a GWP of 1410, non-flammable and suitable for allR-404A systems, including large racks and potential retrofit ofexisting R-404A units. Both refrigerants are thermally stable in presence of air and water andare miscible with POE lubricants. Energy consumption in reach-in freezer and condensing unit tests arecomparable or improved versus R-404A while other performanceparameters are similar.
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