Experimental and Numerical Study of a Mobile Reversible Air Conditioning-Heat Pump System

Electric vehicles suffer from range anxiety, while traditional resistive heating consumes a lot of electric energy and reduces EV drive range largely. Mobile reversible air conditioning-heat pump system is an energy efficient way of providing heat to EV cabin climate. In this paper, an AC/HP system was built based on the Nissan Leaf system configuration and experimentally studied. This system consists of three heat exchangers, an open-shaft compressor, two expansion valves, and two flow control valves. Heating performance of the system under various operating conditions was extensively investigated. Controlling subcooling was found a beneficial way of obtaining higher energy efficiency. Refrigerant charge imbalance when switching modes was found to be a challenge, and was studied both experimentally and numerically. Careful positioning of expansion valves, and sizing of liquid lines in both modes are essential in avoiding large charge imbalance. Component wise, the outdoor heat exchanger holds much more charge in AC mode than in HP mode. A steady state simulation model of the components and the system was developed and reasonably validated against experimental data. Options for improvement of the system based on modeling prediction were provided and discussed