EV Heat Pump Efficiency with the Heat Exchanger Frosted

Abstract

Heating system of EV consumes electric energy for travel and shortens mileage per charge. An electric heater has a simple structure, but its efficiency is low with its cop less than 1. A heat pump system, on the other hand, is more efficient and its heating energy utilization efficiency is higher. However, it has some problems to solve. One of them is frost formation on the heat exchanger surface, and this lowers the heat exchange performance. In the case of the heat pump system for buildings, defrosting operation temporarily stops heating and air blower at outdoor heat exchanger to melt the frost. However, as for EV heat pump system, air blow at heat exchanger cannot be stopped while the vehicle is running. So it keeps operating with frost formation on outdoor heat exchanger. In this paper we study the change of the heating efficiency and the performance under the condition of frost formation.