Thermal Management of a Hybrid Vehicle Using a Heat Pump 2019-01-0502
This paper presents the thermal management of a hybrid vehicle (HV) by using a heat pump system in cold weather. The advantage of an HV is a high efficiency of the vehicle system since an electric motor and an engine are coupled and optimally controlled. However, in the conventional HV, we see the fuel economy degradation in cold weather because delivering heat to the passenger cabin by using an engine results in a low efficiency of the vehicle system. To improve the fuel economy degradation, in this study, a heat pump is used and combined with an engine for the thermal management. The heat pump with an electrically driven compressor pumps heat from ambient into a water-cooled condenser. The heat which is generated by the engine and the heat pump is delivered to the engine and the passenger cabin because the engine needs to warm up quickly to reduce the emission and the cabin needs heat for thermal comfort. To control the heat flow from the engine and the heat pump, a shut-off valve is used in a coolant circuit. We found an optimal way to control the engine and the heat pump in order to minimize the fuel consumption. To this end, we used a 1-D thermal vehicle model for optimization and measured the fuel economy of the optimized system by using a prototype vehicle. Compared to the conventional HV, the fuel economy of the optimized system is improved by 10%.