Low GWP R-404A Alternatives for Commercial Refrigeration Barbara H. Minor Dr. Frank Rinne DuPont Fluorochemicals Chillventa Nűrnberg October 9-11, 2012
Topics Regulatory Environment Properties of New Refrigerants Thermal Stability and Miscibility Thermodynamic Cycle Performance Drop-in System Testing Reach-in Freezer Display Case/Condensing Unit Summary 2
Growing regulatory pressure on HFCs EU F-Gas directive has GWP cap of 150 in new vehicle model a/c systems beginning January 1, 2011; HFC-134a no longer allowed EU EU Commission reviewing F-Gas regulation regarding stationary requirements Australia Instituted carbon tax starting July, 2012 Global Potential for HFC phase-down under the Montreal Protocol framework (cap and allocation) R-404A is a leading target for replacement as it has one of the highest GWPs for HFCs (100 yr 3922 - AR4)
New low GWP Alternatives for R-404A DR-7 2L Mildly Flammable GWP ~250 94% lower GWP than R-404A Suitable for smaller charge R-404A systems due to charge size restrictions in EU codes and standards DR-33 Nonflammable GWP ~1400 65% lower GWP than R-404A For all R-404A systems, including larger systems if nonflammability is required Potential for retrofit of existing R-404A systems
Refrigerant Properties R-404A DR-7 DR-33 100 yr GWP 3922 ~250 ~1400 Flammability None 2L None Boiling Point C -47-48 -46 Critical Point C 72 81 82 Vapor Pressure at 25 C in kpa Liquid Density at 25 C in kg/m3 Vapor Density at 25 C in kg/m3 1254 1372 1271 1044 1133 1139 65.3 46.8 48.9
Thermal Stability Testing Two week accelerated test to simulate the life of HVAC&R equipment (ASHRAE-97) Components are placed in glass tubes under vacuum and sealed Refrigerant DR-7 or DR-33 Lubricant POE 32 centistoke Metal coupons copper, aluminum, carbon steel Optionally air/water added Tubes are exposed at 175ºC for two weeks and analyzed Visual inspection clear fluids and no visible coupon corrosion Fluoride analysis for refrigerant decomposition target at <100 ppm fluoride ion (non detectable at <0.2 ppm)
DR-7 Thermal Stability Testing with POE Lubricant 175ºC for two weeks, air and water Refrigerant DR-7 DR-7 DR-7 DR-7 Oil POE 32 POE 32 POE 32 POE 32 Water (ppm) None 500 None 500 Air (ppm) None None 2000 2000 Fluoride (ppm) 3.7 Non detect 5.2 Non detect DR-7 is thermally stable with POE
DR-33 Thermal Stability Testing with POE Lubricant 175ºC for two weeks, air and water Refrigerant DR-33 DR-33 DR-33 DR-33 Oil POE 32 POE 32 POE 32 POE 32 Water (ppm) None 500 None 500 Air (ppm) None None 2000 2000 Fluoride (ppm) 3.7 Non detect 5.2 Non detect DR-33 is thermally stable with POE
Miscibility Test with POE Lubricant M= miscible Refrigerant:DR-7 Lubricant: POE 32 cstoke Temperature (C) Tube # DR-7/Oil (wt%) -50-45 -40-35 -30-25 -20-15 -10-5 0 5 10 15 20 25 30 35 40 45 50 55 60 1 95 / 5% M M M M M M M M M M M M M M M M M M M M M M M 2 90 / 10% M M M M M M M M M M M M M M M M M M M M M M M 3 85 / 15% M M M M M M M M M M M M M M M M M M M M M M M 4 80 / 20 % M M M M M M M M M M M M M M M M M M M M M M M 5 70 / 30% M M M M M M M M M M M M M M M M M M M M M M M 6 40 / 60% M M M M M M M M M M M M M M M M M M M M M M M 7 30 / 70% M M M M M M M M M M M M M M M M M M M M M M M Refrigerant:DR-33 Lubricant: POE 32 cstoke Temperature (C) Tube # DR-33/Oil (wt%) -50-45 -40-35 -30-25 -20-15 -10-5 0 5 10 15 20 25 30 35 40 45 50 55 60 8 95 / 5% M M M M M M M M M M M M M M M M M M M M M M M 9 90 / 10% M M M M M M M M M M M M M M M M M M M M M M M 10 85 / 15% M M M M M M M M M M M M M M M M M M M M M M M 11 80 / 20 % M M M M M M M M M M M M M M M M M M M M M M M 12 70 / 30% M M M M M M M M M M M M M M M M M M M M M M M 13 40 / 60% M M M M M M M M M M M M M M M M M M M M M M M 14 30 / 70% M M M M M M M M M M M M M M M M M M M M M M M DR-7 and DR-33 are miscible with POE lubricant across wide temperature range
Thermodynamic Cycle Performance Evaporator temperature = -26ºC, Condenser temperature = 43ºC, Subcool amount = 14K, Suction temperature = -4ºC, Compressor isentropic efficiency = 75%. Suct Press kpa Disch Press kpa Comp Ratio Compress Disch Temp C Average Temp Glide C Cap Rel to 404A COP Rel to 404A R-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% DR-7 and DR-33 have comparable capacity and energy efficiency compared to R-404A
System Testing Two Door Reach-in Freezer 1.5 m3 double-door unit designed for R-404A Reciprocating compressor Refrigerant charge size 1.15 kg, adjusted based on liquid density Polyol ester (POE) 32 centistokes lubricant. Tested per AHAM Standard HRF-1-2008 in constant temperature room Tested at three ambient temps: 32ºC, 24ºC and 21ºC Average freezer compartment temp controlled at -17ºC, average evaporator temp -28ºC
Reach-In Freezer Schematic - no equipment changes for DR-7 and DR-33 testing, except TXV closed one turn
Reach-In Freezer Test Results DR-7 and DR-33 Ambient T = 32ºC Energy Cons Rel to R-404A Mass Flow Rate (kg/hr) Suct Press (kpa) Disch Press (kpa) Comp Ratio Comp Disch Temp (ºC) R-404A 100% 44 211 2027 10 90 DR-7 92% 34 191 2133 11 105 DR-33 96% 30 172 1931 11 104 Ambient T = 24ºC R-404A 100% 46 198 1647 8 75 DR-7 95% 35 184 1728 9 91 DR-33 100% 31 172 1551 9 88 Ambient T = 21ºC R-404A 100% 48 199 1558 8 70 DR-7 97% 36 179 1600 9 85 DR-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 Frozen Food Display Case with External Condensing Unit Open Display Case in Indoor Room 2.5 m open frozen food display case designed for R-404A, fully loaded with food simulator Reciprocating compressor with POE 32 oil Refrigerant charge size ~3.8 kg, adjusted based on liquid density Tested per ASHRAE Standard 72-2005 Tested R-404A and DR-33 at two ambient temps: 28ºC and 35ºC in outdoor room, 24ºC in indoor room Only minor TXV adjustment made (1.6 turns closed) Average evaporator temp -34ºC Condensing Unit in Outdoor Room
CONDENSING UNIT AND DISPLAY CASE LAYOUT T Liquid Line P Ps Ts Suction Line To Discharge Line Evap Pressure Regulator Insulated Suction-Liquid Heat Exchange OUTDOOR ROOM Condensing Unit kw Pd Td Mass Flow T Frozen Food Case P T T T P T INDOOR ROOM 28ºC or 35ºC 24ºC ENVIRONMENTAL CHAMBER T, P = TEMP. AND PRESS TAPS
Condensing Unit/Display Case System Test Results DR-33 Ambient T = 28ºC Energy Cons Rel to R404A Mass Flow Rate (kg/hr) Suct Press (kpa) Disch Press (kpa) Comp Ratio Avg Food Temp (ºC) Comp Disch Temp (ºC) R-404A 100% 32 112 1438 13-17 78 DR-33 97% 26 104 1407 14-17 83 Ambient T = 35ºC R-404A 100% 33 127 1722 14-16 87 DR-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
Summary New low GWP refrigerants for R-404A under development DR-7 has a GWP of ~250, is mildly flammable (2L) and suitable for single condensing unit systems, stand-alone coolers and freezers. DR-33 has a GWP of ~1400, non-flammable and suitable for all R-404A systems, including large racks and potential retrofit of existing R-404A units. DR-7 and DR-33 are thermally stable in presence of air and water and are miscible with POE lubricants. Energy consumption in reach-in freezer and condensing unit tests are comparable or improved versus R-404A while other performance parameters are similar.
Questions? Come see us at Hall 4 Stand 410 Thank you! Email: barbara.h.minor@usa.dupont.com frank.rinne@de.dupont.com Disclaimer: The information set forth herein is furnished free of charge and based on technical data that DuPont believes to be reliable. It is intended for use by persons having technical skill, at their own risk. Since conditions of use are outside our control, we make no warranties, expressed or implied and assume no liability in connection with any use of this information. Nothing herein is to be taken as a license to operate under, or a recommendation to infringe any patents or patent applications.