Numerical and experimental analysis of air-cooled Lithium-ion battery pack for the evaluation of the thermal performance enhancement

Abstract

The main objective of this study is to assess the thermal performance of an air-cooled Lithium-ion battery pack. This involves analyzing the heat dissipation characteristics and temperature distribution within the battery pack at different operating conditions. Here, the thermal performance of the battery pack is evaluated numerically and experimentally. The experimental platform allows adjusting numerous control factors, like air velocity (0.5 to 2.0 m/s), air temperature (282.0 to 315.0 K), and battery pack discharge rate (0.5 to 2.5C). The temperature distribution is studied in longitudinal and transverse directions of the battery pack and circumferentially for a cell. The numerical simulations involve the solution of Shear Stress Transport (SST) k- ω model-based Navier-Stokes (N-S) equation using the ANSYS FLUENT R19.2 software. The numerical results were found to closely match the experimental findings with maximum error to be within 3.12%. The evaluation parameters used to assess the thermal performance of BTMS are maximum temperature(Tmax), maximum temperature difference (∆Tmax), average temperature (Tavg.), and standard deviation of the temperature σT within the battery pack. The numerical and experimental analyses show a reduction in both the maximum and mean temperature of the battery pack and improved temperature uniformity, with the increase in air velocity, lowering the discharge rate and decreasing the ambient temperature. The correlation between air inlet velocity and temperature drop is stronger at higher discharge rates than lower discharge rates. The effect is due to high heat transfer coefficient and uniform air distribution at high velocities, less heat generation and more time to dissipate heat at low discharge rates, and lower temperature of air at cold ambient conditions. The reduced temperatures and temperature uniformity minimizes the occurrence of localized hotspots within the battery pack. Further, for any given air inlet temperature, an increase in temperature is observed parallel to the direction of airflow. Under severe operating conditions, the inlet-to-discharge temperature difference reached a maximum of T = 22.14 K whereas, under mild conditions, it dropped to T = 0.21 K. The circumferential temperature non-uniformity of cells lying in high-temperature zone of the battery pack reduces with increasing velocity. The work presented here can help in the identification of potential hotspots and design better cooling strategies for the battery pack at different operating conditions.