Analogies in the Analysis of the Thermal Status of Batteries and Internal Combustion Engines for Mobility

Thermal management is an important research area for the automotive sector in order to make high-efficiency and low-impact future vehicles. The transition from internal combustion engines to battery systems in the automotive field requires new skills to be achieved in the shortest possible time. The well-consolidated knowledge of thermal management of engine systems can be rearranged to face new challenges regarding the thermal control of batteries. The present work aims to show the analogies between the thermal behavior of an engine component, such as the piston, and of a battery. The thermodynamic processes involved during the operation are described, experimentally investigated, and modeled. The external temperature of the piston window is measured once per cycle with a K-type sheathed thermocouple, while the surface temperature of the battery is detected via infrared imaging. An almost-fixed stabilization time of 500 s is observed for the engine while it varies with the current load for the battery ranging from 1800 s to 3000 s, for the tested cases. Different temperature increments are also observed. Two mono-dimensional (1D) models of heat transfer are built using the finite-difference method. Good agreement with the experimental data is quantitatively demonstrated by a Normalize Root Mean Square Error lower than 0.07 for all the test cases and systems, except for the battery charging phase. The analysis of the temperature provides an estimation of the heat losses for the two systems, spanning from 15% to 27% for the engine and from 6% to 10% for the battery. The analysis carried out in this work can provide a methodology to understand and improve the thermal management of the new mobility system.