Thermal management scheme and optimization of cylindrical lithium-ion battery pack based on air cooling and liquid cooling

Battery thermal management system (BTMS) ensures the batteries work in a safe and suitable temperature range. In this study, a hybrid BTMS based on air cooling and liquid cooling is proposed. The heat generated by the battery is transferred to the coolant by heat conducting blocks (HCBs) which are evenly spaced along the axial direction of it to maintain the normal operation of the battery pack. Air cooling is then introduced to maintain the battery's temperature uniformity at the battery pack's edge. A three-dimensional simulation model was designed and established to explore the number and size of HCBs, the effects of flow rate and the addition of air cooling on the comprehensive performance of BTMS. The results indicate that a good balance of cooling performance, power consumption, and lightweight will be achieved when the number of HCBs is three, the diameter of the cooling channel on the heat exchanger block is 6 mm and the flow rate of each cooling channel is 0.002 kg/s. In this case, the maximum temperature (T_max) is 34.41 °C and the maximum temperature difference (ΔT) is 1.53 °C. The addition of air cooling lowers T_max and ΔT by 3.75 °C and 0.96 °C, respectively, and lowers the maximum temperature difference of single battery cell from 6.31 °C to 3.86 °C. Additionally, when intermittent air cooling is used, system power consumption is decreased while the battery pack can operate within the proper temperature range.