Numerical investigation on thermal characteristics of a liquid-cooled lithium-ion battery pack with cylindrical cell casings and a square duct

The thermal management of Lithium-Ion batteries has gained significant attention in the automobile industry. An efficient battery cooling system particularly active cooling techniques have opted as a promising solution in commercial electric vehicles. The physical structure and configuration of the battery pack play a crucial role while designing the battery cooling systems. In the present article, a novel design of a battery pack is designed which includes the cylindrical casings to insert batteries into it and a liquid cooling medium is circulated in its surrounding. This acts as a midway solution between the direct and indirect liquid cooling techniques. The battery cooling system has been numerically modeled using a finite volume approach and theoretically investigated to analyze the thermal behavior of battery systems. The thermal performance of the twenty-five 18,650 Lithium-Ion battery cells arranged in a 5 x 5 configured battery module is evaluated using a forced-liquid cooling system. A detailed thermal analysis has been performed under different discharge rates of 0.5C, 1C, 2C, 3C, 4C, and 5C to determine the impact of heat generation on the battery thermal performance. The numerical model is validated with the empirical correlations of heat transfer for the accuracy of the proposed design. The results reveal that the proposed design minimizes heat accumulation by enhancing the exposure of the cell casings to the heat transfer medium. An even distribution of coolant to each cell provides uniform temperature distribution within the battery module. Further, the effect of natural convection has also been investigated and the results reveal that the maximum temperature rise has been reduced to a great extent at a convective heat transfer co-efficient of 25 W/m(2) K. Furthermore, an overall battery pack temperature below 28 degrees C is recorded at 0.5C and even at a higher discharge rate of 5C for 720 s, and the maximum temperature between adjacent cells is limited to 0.12 degrees C.