CFD Simulation and Modelling of a Battery Thermal Management System: Comparison between Indirect and Immersion Cooling

Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) are becoming relevant in the transportation sector, and it is therefore of utmost importance to find a solution to allow batteries to work safely and in a correct temperature range in which performance degradation and/or thermal runaway do not occur. For this purpose, a Battery Thermal Management System (BTMS) is required to ensure the correct operation of the battery pack. The design and control of an efficient BTMS is a complex task, in which multiple technical fields are involved. The paper mainly focuses on the thermal problems affecting the BTMS and sets two main goals: 1) to provide a comparison of two possible BTMS solutions, analyzing constraints and thermal performance for the design task; 2) to present a battery thermal 1D model able to describe the battery module behavior in real-time application to be implemented in a BMS control. The design workflow of the two BTMS proposed solutions, indirect liquid-based cooling plate and direct immersion liquid cooling, is investigated in this paper. A CFD simulation is performed to evaluate the local temperature hot spot, thermal gradient and the global thermal performance of the systems. Subsequently, to overcome the issue of high computational cost of CFD simulation, a first 1D thermal model of the immersion liquid cooling solution is properly developed for temperature evolution estimation in real-time applications. The results of the CFD simulations and of the 1D model are compared to assess the accuracy of the 1D model.