An investigation on dehumidification and heat transfer characteristics of a minichannel heat exchanger for heat pump system of electric vehicles

Abstract

Heat pump systems for electric vehicles must assure the system's energy efficiency and the comfort and safety of the passenger cabin. This project aims to analyze the dehumidification and heat transfer characteristics of a heat exchanger through experiments and theoretical modeling. In this paper, a parallel flow minichannel heat exchanger was experimentally and theoretically studied under various operating conditions. A distributed parameter model considering heat and mass transfer was developed and utilized to predict the heat exchanger's dehumidification and heat transfer characteristics. The results reveal that, with a fixed inlet air relative humidity and a low refrigerant mass flow rate, the dehumidification rate (DHR) increases and subsequently declines with the increasing inlet airflow. When the inlet air relative humidity and inlet airflow are constant, the lower the refrigerant mass flow rate, the greater the enthalpy humidity ratio. As the inlet airflow increases, the refrigerant mass flow rate and inlet air relative humidity stay constant, and the enthalpy humidity ratio rises. The proposed model's predictions match the experimental data rather well. The predicted heat transfer rates (HTRs) and DHRs have absolute errors of less than 4% and 10%, respectively, compared with the experimental results. Under various airflows for the OM3 operating conditions, the distributions of HTR and DHR demonstrate that the HTR percentage is lowest in flow path IV, no dehumidification is conducted in flow path IV, and the DHR percentage is largest in flow path II. The proposed model may be employed to assess the dehumidification and heat transfer performance of heat exchangers and optimize the design of heat exchangers in similar heat pump systems. Highlights Construct a test bench for the dehumidification and heat transfer performance evaluation of a minichannel evaporator. Analyze and discuss the dehumidification and heat transfer characteristics of the evaporator under different operating conditions. Develop a distributed parameter model of dehumidification and heat transfer for the evaporator.