Investigation of the Effect of Thermal Interface Materials on the Cooling of Battery Cells: A comparative study on the heat transfer properties

Examensarbete för masterexamen
Master's Thesis
Mobility engineering (MPMOB), MSc
Maddila, Rohith Virinchi
Rostami, Soroush
The transport sector has been a significant contributor to the rising carbon footprint, primarily due to the use of fossil fuels as a power source. To mitigate this issue, the concept of electromobility has emerged, emphasizing electrically driven vehicles with batteries for various transportation modes. Enhancing battery efficiency is crucial for improving the performance of electric vehicles, achieved through an efficient Battery Thermal Management System (BTMS). The BTMS aims to optimize heat transfer from the battery, ensuring it functions within the operating temperature range. Among the effective BTMS approaches, the liquid cooling system stands out, aided by a Thermal Interface Material (TIM) placed between the batteries and the cooling plate. This master thesis, conducted in collaboration with ESS Component and Verification group in Electromobility at Volvo GTT, investigates the performance of commercially produced TIMs. Key parameters such as TIM thickness and applied pressure are altered to assess their impact on TIM performance. This investigation employs a complementary approach of experimentation and simulation to study two different Thermal Interface Materials (TIMs): a thermal pad and a thermal gel. The focus of this thesis is on the thermal conductance of the TIMs, which is represented by a dummy cell maintained in a steady state of heating during the experimentation. The study begins by examining the thermal pad, with an emphasis on varying the applied pressure to evaluate its impact. Subsequently, a comparative study is conducted on the thermal gel, exploring the effects of both thickness and pressure on heat transfer through the TIM. The objective is to enhance heat dissipation and subsequently cool the battery. Through analysis and a review of existing literature, simulations were carried out to understand the effect of the thermal properties of these TIMs on the cooling of the batteries. A comparative investigation was carried out using experimentation and simulations to examine the impact of varying the thickness of TIMs on the temperature of a simulated cell. The results indicated that when the TIM possessed a higher effective thermal conductance, achieved by increasing the pressure applied to it, the cell's temperature decreased. This outcome was consistent for both a 2 mm thermal pad and a 2 mm thermal gel. However, when the gel thickness was reduced to 0.5 mm, applying high pressure led to cracks inside of it which in turn led to a reduction in effective thermal conductance. The obtained results demonstrated that the highest pressure led to a 40% reduction in the thermal resistance for the 2 mm pad, while it was only a 16% reduction for the 2 mm gel.
Heat transfer , BTMS , Dummy cell , TIM , Effective thermal conductance , Thermal resistance
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