Experimental evaluation of an integrated electric vehicle AC/HP system operating with R134a and R407C

An integrated air conditioning/heat pump (AC/HP) system for electric vehicle (EV) was developed and the system heating performances under low temperature were quantitatively evaluated. The AC/HP system employed electric scroll compressor to achieve high compressor speed. The heat exchangers were derived from the original EV air conditioning system. A four-way reversing valve was used to switch the system working modes between AC and HP. Heating tests using R134a and R407C as refrigerants were conducted respectively in an environmental chamber. The cabin temperature, the compressor power and other variables were analyzed to evaluate the system heating capability and energy efficiency. Test results showed that the AC/HP system satisfied the EV cabin heating requirement at the ambient temperature -10°C. It reduced the EV power consumption remarkably compared to the original PTC heater. But the system performance was greatly affected by the ambient temperature. Compared to R134a, the system heating capability and the compressor power of R407C were increased but the energy efficiency was reduced. Increasing the compressor speed could limitedly improve the heating capacity, especially at the decreased ambient temperature. But it would reduce the energy efficiency distinctly. Test results also implied that the system performance has the potential for improvement.