Thermal management analysis of a 280 Ah prismatic LFP battery module with PCM and a thermal bridge : a transient CFD study under 0.5C and 1C discharge conditions

Abstract

This paper investigates the thermal response of a 280 Ah prismatic lithium iron phosphate battery module with a phase change material (PCM) layer and a thermal bridge between cells under 0.5C and 1C discharge conditions. A three-dimensional transient thermal model was established based on ANSYS Fluent, and two structural forms were compared: one is a PCM-coated dual-cell structure without a thermal bridge, and the other is a structure with a thermal bridge between two cells. All four main operating conditions were conducted at an ambient temperature of 25 °C. The battery region was modelled as an orthotropic solid with a density of 2130 kg/m³, a specific heat capacity of 1020 J/(kg·K), and thermal conductivities of 0.923, 0.911, and 19.375 W/(m·K) in the three main directions. The PCM region adopted the density and thermal conductivity parameters of RT44HC, and the latent heat effect of phase change was approximated by a temperature-dependent apparent specific heat capacity curve instead of using a fixed specific heat capacity assumption.

The results show that the discharge rate is the dominant factor affecting the module temperature. For the structure without a thermal bridge, the maximum battery temperature increases from 314.03 K at 0.5C to 326.73 K at 1C, and the average PCM temperature rises from 301.91 K to 303.24 K. For the structure with an aluminium thermal bridge, the peak battery temperature changes from 314.02 K to 327.04 K, and the average PCM temperature changes from 301.86 K to 303.18 K. The results indicate that increasing the discharge rate significantly increases the thermal load, and under the current geometric dimensions, the effect of the thermal bridge is relatively weak. The supplementary sensitivity analysis of the copper thermal bridge shows that compared with the aluminium thermal bridge, the copper thermal bridge only brings a very small decrease in peak temperature, which indicates that the main thermal resistance in the current model is not determined by the thermal conductivity of the bridge material. The mesh independence analysis for Case 4 shows that the changes in key thermal indicators under coarse, medium, and fine mesh groups are all less than 0.03 K, indicating that the results have good mesh independence. Overall, this paper demonstrates that the simplified transient thermal model can still provide valuable engineering comparison basis for the thermal management of large-capacity square battery PCM.