Experimental study on vapor injection air source heat pump with internal heat exchanger for electric bus

In this paper, a vapor injection ASHP unit is developed for electric bus and the heating performance is experimentally studied with the adjustment of compressor frequency under different working conditions. The optimum compressor frequency depends on the working conditions and at higher inlet air temperature of condenser the higher compressor frequency is better. Under the working condition of-20/20 degrees C and 85 Hz, COP of the ASHP with vapor injection is 1.60 and improves by 14.5% against that of no-injection. Under the working condition-20/5 degrees C and 85 Hz, it is 2.22 and decreases by 2.9% against that of no-injection. The results show that the advantage of vapor injection is reflected in the conditions of higher temperature difference between the evaporator and condenser. According to the comparison of COPc, vapor injection is more beneficial as the heating capacity can't meet the heating demand. (C) 2019 The Authors. Published by Elsevier Ltd.