Experimental investigation on the heating performance of a R410A vapor-injection heat pump of an electric bus in cold regions

Abstract

To study the heating performance of a R410A SCVI (sub-cooler vapor-injection) heat pump of an electric bus and solve its practical application problems in cold regions, the experimental setups were established. The experimental tests were carried out in the enthalpy difference chamber. The influence of ambient temperature, compressor speed, vapor-injection mass flow ratio and indoor air temperature on the system were considered. The minimum ambient temperature for the experiment is −25 °C. The results show that when the compressor speed increases from 3000 rpm to 5400 rpm, the heating capacity increases by 43.7 % but the COP (coefficient of performance) decreases by 11.1 %. As the ambient temperature decreases, the heating capacity of N-VIHP (non-vapor-injection heat pump) decreases more. The heating capacity of the VIHP (vapor-injection heat pump) system has a maximum increase of 3.84 kW, with an overall increase of 4.9 % ∼ 33.2 %, and the increase of COP is 2.7 % ∼ 15.2 % compared with N-VIHP. The optimal vapor-injection mass flow ratio is 0.32 ∼ 0.44 for this electric bus R410A SCVI heat pump. The vapor-injection circuit electronic expansion valve does not need to be opened all the time. It is better to open it when the ambient temperature is below −5 °C. The VIHP has better heating performance at low temperature and is more suitable for electric buses in cold regions.