Characteristics of the operation of a micro-heat pump for electric vehicles with respect to applied voltages

It is necessary to analyze the operation characteristics of a heat pump under various applied voltages to develop a micro-heat pump for electric vehicles because the voltage of the battery in electric vehicles is linearly reduced with respect to the usage time after a full battery charge. In this study, the operation characteristics of a micro-heat pump were investigated with respect to applied voltages. Cooling and heating experiments were conducted by a using micro-heat pump in an isothermal-isohumidity control chamber. External temperatures of 27 °C and 35 °C were used for the cooling operations and 24 °C and -7 °C were used for the heating operations. The applied voltages were varied from 16 to 32 V at an interval of 2 V. As the applied voltage was increased, cooling and heating capacities increased by up to 51 %, 54 %, 43 %, and 33 % at external temperatures of 27 °C, 35 °C, 24 °C, and -7 °C, respectively. The coefficient of performance increased by up to 35 %, 39 %, 22 %, and 10 % as the applied voltage was increased at external temperatures of 27 °C, 35 °C, 24 °C, and -7 °C, respectively.