Using fins to enhance heat transfer of cylindrical lithium-ion batteries immersed in electrical insulating oil

This work focused on designing the heat dissipation fins for cylindrical lithium-ion batteries to quickly transfer the heat generated inside the battery to the surrounding immersed insulating oil. The measured instantaneous heat generation rate of a single battery at the discharge rates of 1.0C and 1.5C was adopted as the internal heat source to simulate the surface temperature field of two series and two parallel (2S2P) battery modules immersed in insulating oil in three-dimensional space, respectively. The numerical simulation method has been validated by experimental results, indicating that the scheme of using this internal heat source is feasible. Then, this method was continued to be used to simulate the temperature rise characteristics during higher rate 2.5C discharge processes when the heat transfer was enhanced by circular or serrated fins. The cooling effects of three heat exchange enhancement methods (no fins, circular fins, and serrated fins) were compared under the operating conditions of 25 degrees C ambient temperature, and 1 g center dot s(-1) rated insulation oil circulation mass flow rate. The maximum temperatures of the batteries in the module were 40.3 degrees C, 38.4 degrees C, and 37.5 degrees C, respectively. The maximum temperature differences between the batteries in the module were 1.63 degrees C, 1.59 degrees C, and 1.51 degrees C, respectively. Therefore, the serrated fins had the best thermal management effect. The orthogonal method was used to analyze the influence of the external structure and quantity of fins, as well as the insulation oil circulation mass flow rate, on heat transfer efficiency, and it was determined that the most significant factor is the mass flow rate of insulation oil. The final optimal parameters suitable for the 2S2P battery module were obtained, which were 16 serrated fins for each battery, with a fin height of 6 mm, a fin width of 3 mm, and a mass flow rate of 7 g center dot s(-1).