R1234yf System Enhancements and Comparison to R134a June 10, 2008 John Meyer
R1234yf Agenda System Performance Evaluation TXV (Egelhof) and MCV (TGK) tuning Baseline and enhanced system test results» IHX» Oil Separator» High Effectiveness Evaporator Compressor Durability
P-T for R134a and R1234yf 3500 3000 Pressure [kpaa] 2500 2000 1500 1000 R134a R1234yf R1234yf has higher saturation pressure Cross at ~30C R1234yf has lower saturation pressure 500 0-10 0 10 20 30 40 50 60 70 80 90 Temperature [C]
R134a Stand Evaluation Production system used for analysis 160cc variable displacement compressor 16mm IRD condenser 2.0T cross-charged TXV 58mm plate-fin evaporator Slightly modified discharge and liquid line Modified for installation on stand Slightly modified SL To allow for in situ torque calibration
R1234yf Stand Evaluation Changes to R134a system hardware Same 16mm IRD condenser Same 58mm plate-fin evaporator Same VS16 compressor, new MCV set points Same 200 cc PAG 2.0T, 2.5T, 1.75T TXVs at high & low SH settings evaluated Same slightly modified discharge and liquid line Same slightly modified SL to allow for torque calibration
Evaluation Matrix Compressor Condenser Airflow Evaporator Airflow Temp Flow Temp RH RPM l/s C l/s C % 1 2500 700 45 140 43 40 2 1800 650 45 140 43 40 3 800 600 45 140 43 40 4 2500 700 37 140 35 40 5 1800 650 37 140 35 40 6 800 600 37 140 35 40 7 2500 700 27 100 25 40 8 1800 650 27 100 25 40 9 800 600 27 100 25 40
R134a Charge Determination 2100 560 g chosen 24 2050 20 Pressure [kpag] 2000 1950 1900 Disch P 16 12 8 Temperature [C] Air out T 1850 SH SC 4 1800 300 350 400 450 500 550 600 650 Charge [g] 0
R1234yf Charge Determination 1950 1900 550 g 24 20 Pressure [kpag] 1850 1800 1750 16 12 8 Temperature [C] 1700 Pdisch SC Evap SH disch air 4 1650 0 300 350 400 450 500 550 600 650 Charge [g]
14 Adjusting R1234yf SH TXVs have a set screw to adjust SH setting Each valve was evaluated at a high and low SH setting 35C, 1800RPM (pt 5) COP, SC, SH, Capacity 12 10 8 6 4 2 Evap SH Subcool COP Capacity 0 0 1 2 3 4 5 # of 60 degree CCW turns of the TXV
R1234yf vs R134a; Evaporator SH Temperature [C] 18 16 14 12 10 8 6 4 2 R134a baseline R1234yf 2T high SH R1234yf 2T low SH R1234yf 2.5T high SH R1234yf 2.5T low SH R1234yf 1.75T high SH R1234yf 1.75T low SH SH comparison 1.75T TXV (blue) seems to lose Control of SH at high loads 0 800 1800 2500 800 1800 2500 800 1800 2500 9 8 7 6 5 4 3 2 1 25C Point 35C 43C
R1234yf TXV and MCV Evaluation Cross charge TXVs from Egelhof 2.0, 2.5, and 1.75T valves tested 1.75T TXV is undersized TXV at low SH Although no strong indication that low SH leads to improved performance:» Low SH facilitates IHX integration» Improved evaporator discharge air stratification MCVs from TGK Initial MCV calibration slightly off Gen II MCVs better tuned for this system
R1234yf Evaporator Stratification 4x4 thermocouple matrix on evaporator outlet Stratification = T max T min With similar SH settings, R1234yf shows slightly improved stratification
Baseline R1234yf System Defined Same compressor, heat exchangers, lines, lubricant 2.0T TXV from Egelhof at low SH setting GEN II MCV from TGK
R1234yf Enhancements Internal Heat Exchanger (IHX) Production Intent (SOP 09) Fully validated with R134a Oil Separator High efficiency evaporator Tube-fin Same package Lower air-side pressure drop
R134a vs 1234yf IHX; Capacity 8 7 6 R134a baseline R134a IHX R1234yf baseline R1234yf IHX Capacity [kw] 5 4 3 MCV controls capacity 2 1 0 800 9 1800 8 2500 7 800 6 1800 5 2500 4 800 3 1800 2 2500 1 25C Point 35C 43C
R134a vs 1234yf IHX; Efficiency 5.0 4.5 4.0 R134a baseline R134a IHX R1234yf baseline R1234yf IHX 3.5 COP [ - ] 3.0 2.5 2.0 1.5 1.0 0.5 0.0 800 1800 9 8 7 6 5 4 3 2 1 25C 2500 800 1800 35C Point Number 2500 800 1800 43C 2500
Discharge and Pressure Ratio 2200 11 Pressure [kpag] 2000 1800 1600 1400 1200 1000 800 600 P [kpag] R134a [C] 1234yf [C] 1700 62.9 65.0 1800 65.2 67.5 1900 67.5 69.9 2000 69.6 72.2 R134a R1234yf R134a R1234yf 10 9 8 7 6 5 4 3 Pressure Ratio [ - ] 400 200 0 9 8 7 6 5 4 3 2 1 800 1800 25C 2500 800 P-T relationship predicts ~100kPa lower discharge pressure for R1234yf 1800 Point 35C 2500 800 1800 43C 2500 2 1 0
Temperature [C] 120 110 100 90 80 70 60 50 40 30 20 10 0 R134a vs 1234yf IHX; Compressor Discharge Temperature R134a Baseline R134a IHX R1234yf baseline R1234yf IHX 800 9 1800 8 2500 7 800 6 1800 5 2500 4 800 3 1800 2 2500 1 25C Point 35C 43C
R134a vs 1234yf Oil Separator & High Efficiency Evaporator; Capacity Capacity [kw] 8 7 6 5 4 3 R134a baseline R1234yf baseline R1234yf Oil Sep R1234yf HE evap MCV controls capacity 2 1 0 800 9 1800 8 2500 7 800 6 1800 5 2500 4 800 3 1800 2 2500 1 Point 25C 35C 43C
R134a vs 1234yf Oil Separator & High Efficiency Evaporator; Efficiency 5.0 4.5 4.0 R134a baseline R1234yf baseline R1234yf Oil Sep R1234yf HE evap 3.5 COP [ - ] 3.0 2.5 2.0 1.5 1.0 0.5 0.0 9 8 7 6 5 4 3 2 1 800 1800 25C 2500 800 1800 2500 Point Number 35C 800 1800 43C 2500
Evaporator Inlet Quality Higher quality = less liquid = lower capacity Quality [ - ] 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 R134a R1234yf Inputs 10 C Subcool 5 C Evaporation temp Supercritical R744 highside pressure = 13MPa 8% Less Liquid 20 30 40 50 60 70 80 Condensing Temperature [C]
Evaporator Inlet Quality Higher quality = less liquid = lower capacity Quality [ - ] 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 R134a R1234yf R744 Inputs 10 C Subcool 5 C Evaporation temp Supercritical R744 highside pressure = 13MPa 29% Less Liquid 8% Less Liquid 20 30 40 50 60 70 80 Condensing Temperature [C]
R1234yf Performance Summary Baseline R1234yf system used same tonnage TXV with modified bulb charge and adjusted MCV R1234yf has approximately 8-10 C cooler compressor discharge temperature vs R134a As near drop-in, capacity and efficiency fall slightly short of R134a
R1234yf Performance Summary (cont) R1234yf with IHX ~Matches/exceeds R134a baseline capacity Has slightly higher average efficiency than baseline R134a across all points ~Matches R134a compressor discharge temperature R1234yf with Oil Separator Small increase in capacity and efficiency Falls short of baseline R134a at high ambient R1234yf with High Efficiency Evaporator Small increase in capacity and efficiency Falls short of baseline R134a at high ambient
R1234yf Compressor Testing Initial Compressor Durability High Pressure Low Charge high load and temperature test» Completed initial testing - No issues High Speed high friction and high temperature test» Completed initial testing No issues
Durability Teardown Results
Acknowledgements Thanks to. for prototype MCVs Egelhof for prototype TXVs JCS for tube-fin evaporator Honeywell and DuPont for R1234yf