Experimental investigation on the R1234yf air conditioning system with a battery cooling loop under realistic conditions of electric vehicles

The air-conditioning system of an electrical vehicle (EV) with a cooling loop for battery was experimentally investigated at medium to high load conditions, using R1234yf as refrigerant. Optimal filling rates of R1234yf and R134a were first determined as 975 g with the battery cooling loop closed. Then, the system performance regarding the two refrigerants with optimal charges was compared with various chiller thermal loads at maximum cabin cooling capacity condition as well as nine high load conditions. It was found that using R1234yf as the alternative of R134a, the HVAC cooling capacity, the power consumption of the compressor and the coefficient of performance (COP) decreased by 23.6%, 10.5%, and 8.1%, respectively, at maximum cooling capacity condition with a chiller load of 1.5 kW. At high load conditions with various chiller thermal loads, the reductions of HVAC cooling capacity and power consumption were 8.2%-29.8% and 3.2%-19%, respectively, resulting in a decrease in COP of 1%-16.3%. Thirdly, it was presented that, for R1234yf, at high vehicle speed conditions with the TXVs as original setting, the outlet air temperature of the HVAC box increased about 2.4 degrees C, with the power consumption increased by 17.3%, if the chiller thermal load was increased from 0 to 2.5 kW. Other main conclusion included that, at idle condition, for the R1234yf system with the chiller loop on, the outlet temperature of the HVAC box and COP decreased by 2.7 degrees C and 37.1%, respectively, when the compressor speed increased from 4000 to 7000 rpm.