This study investigated the cooling performance characteristics of the electrical air conditioning
system using R744 for a fuel cell electric vehicle. In this investigation, the inlet air conditions of both
gas cooler and evaporator and the compressor speed were varied. Experimental results showed that the
cooling capacity and cooling COP of the electrical air conditioning system using R744 were sufficient
to cover the cooling load of the fuel cell electric vehicle under hot weather conditions and the cooling
capacity and the cooling COP of the tested system increased up to 6.4 kW and 2.5, respectively. As a
result, the developed electrical air conditioning system could be very helpful for improving the driving
efficiency of the fuel cell electric vehicle because it would consume less electric energy from the high
voltage battery system and provide higher cooling COP. In addition, the electrical air conditioning
system with R744 using an inverter driven compressor showed better performance than the
conventional air conditioning system with R-134a under the same operating conditions.
(1) The cooling COP and the cooling capacity increased by 30.3% up to 2.5 and 36.8% up to
6.4 kW, respectively, with the rise of the gas cooler inlet pressure from 92.0 bar to 102.0 bar at the
gas cooler inlet temperature of 35.0 °C and the compressor speed of 4000 rev/min.
(2) The cooling capacity increased with rise of the compressor speed but the cooling COP was
reduced because the compressor work increased due to the increased compression ratio and
specific volume at the compressor inlet.
(3) At the gas cooler inlet pressure of 90.0 bar, the cooling COP and the cooling capacity decreased
by 55.6% and 55.1%, respectively, with the rise of the gas cooler air inlet temperature from 27 °C
to 42 °C due to the decreased heat transfer efficiency of the gas cooler.
(4) Under extremely hot weather conditions over 35.0 °C, the cooling capacity of the tested system
was sufficient, over 5.0 kW, at the compressor speed over 4500 rev/min.
(5) The cooling COP of the electrical air conditioning system using R744 was on average 24.3%
higher than that using R-134a at all compressor speeds.