Electric vehicles (EVs) are incorporated with higher energy density batteries to improve the driving range and performance. The lithium-ion batteries with higher energy density generate a larger amount of heat which deteriorates their efficiency and operating life. The currently commercially employed cooling techniques are not able to achieve the effective thermal management of batteries with increasing energy density. Direct liquid cooling offers enhanced thermal management of battery packs at high discharging rates compared to all other cooling techniques. However, the flow distribution of coolant around the battery module needs to be maintained to achieve the superior performance of direct liquid cooling. The objective of the present work is to investigate the heat transfer characteristics of the lithium-ion battery pack with dielectric fluid immersion cooling for different fin structures. The base structure without fins, circular, rectangular and triangular fin structures are compared for heat transfer characteristics of maximum temperature, temperature difference, average temperature, Nusselt number, pressure drop and performance evaluation criteria (PEC). Furthermore, the heat transfer characteristics are evaluated for various fin dimensions of the best fin structure. The heat transfer characteristics of the battery pack with dielectric fluid immersion cooling according to considered fin structures and dimensions are simulated using ANSYS Fluent commercial code. The results reveal that the symmetrical temperature distribution and temperature uniformity of the battery pack are achieved in the case of all fin structures. The maximum temperature of the battery pack is lower by 2.41%, 2.57% and 4.45% for circular, rectangular, and triangular fin structures, respectively, compared to the base structure. The triangular fin structure shows higher values of Nusselt number and pressure drop with a maximum value of PEC compared to other fin structures. The triangular fin structure is the best fin structure with optimum heat transfer characteristics of the battery pack with dielectric fluid immersion cooling. The heat transfer characteristics of a battery pack with dielectric fluid immersion cooling are further improved for triangular fin structures with a base length -to -height ratio (A/B) of 4.304. The research outputs from the present work could be referred to as a database to commercialize the dielectric fluid immersion cooling for the efficient battery thermal management system at fast and higher charging/discharging rates.

The cooling performance of the air-conditioning system in electric vehicles could be enhanced through the geometrical optimization of the air ducts. Furthermore, it has been proven that the heat-transfer performance of divergent channels is better than that of conventional channels. Therefore, the present study investigates the thermal and flow characteristics of divergent ducts with various rib shapes for the cooling system of electric vehicles. The thermal and flow characteristics, namely, temperature difference, pressure drop, heat-transfer coefficient, Nusselt number and friction factor, are numerically studied. Divergent ducts comprising ribs with the different shapes of rectangle, isosceles triangle, left triangle, right triangle, trapezoid, left trapezoid and right trapezoid arranged symmetrically are modeled as the computational domains. The thermal and flow characteristics of divergent ducts with various rib shapes are simulated in ANSYS Fluent commercial software for the Reynolds-number range of 22,000–79,000. The numerical model is validated by comparing the simulated results with the corresponding experimental results of the Nusselt number and the friction factor, obtaining errors of 4.4% and 2.9%, respectively. The results reveal that the divergent duct with the right-triangular rib shape shows the maximum values of the heat-transfer coefficient and Nusselt number of 180.65 W/m2K and 601, respectively. The same rib shape shows a pressure drop and a friction factor of 137.3 Pa and 0.040, respectively, which are lower than those of all rib shapes, except for the trapezoidal and right-trapezoidal rib shapes. Considering the trade-off comparison between thermal and flow characteristics, the divergent duct with the right-triangular rib shape is proposed as the best configuration. In addition, the effect of various conditions of the inlet air temperature on the thermal characteristics of the best configuration is discussed. The proposed results could be considered to develop an air-duct system with enhanced efficiency for electric vehicles.