Analysis of a Battery Thermal Management System for Electric Vehicles using Heat Pipe Technology

Abstract

This paper presents an analysis of the performance of a heat pipe assisted battery thermal management system (BTMS) as a means of passive heat dissipation from EV batteries to minimise required pumping power. A BTMS incorporating both standard heat pipes and multi-branched heat pipes (MBHPs) is analysed. The standard heat pipe configuration is analysed experimentally using a custom-built test rig and numerically using thermal equivalent circuit (TEC) models developed using MATLAB’s Simscape software. The MBHP setup is analysed numerically having validated the TEC models using the experimental data from the standard configuration. Experimental results showed that the standard heat pipe BTMS provided sufficient cooling at heat loads of <40W. However, at heat loads of 40W the maximum battery temperature marginally exceeded the maximum temperature criteria with a maximum battery block temperature of 42.9 o C and temperature difference between battery blocks of 4.3 o C recorded. Due to an increase in heat transfer coefficient with increasing coolant flow rate, the battery block temperature and temperature difference decrease. This decrease in temperature is counteracted by a decrease in the coefficient of performance of the cold plate by approximately 70% as pumping power increases due to increased pressure drop across the cold plate. This showed there are marginal gains to increasing flow rate in the BTMS. Numerical analysis of both setups shows a similar temperature response of the simulated batteries to the experimental setup with analytical results being within 15% the of experimental values. Therefore, a TEC can be used to predict battery temperatures. Numerical results show increased battery temperature for an MBHP setup but kept within the operating range for heat loads of <20W suggesting MBHP’s can perform sufficiently for normal battery discharge rates.