Numerical investigation of a cylindrical lithium-ion battery pack with integrated phase change material and coolant circulating channels

Abstract

The integration of passive cooling (PCM) and active cooling as a battery thermal management system integrate the advantages of attaining a low maximum cell temperature and maintaining temperature uniformity in the battery module. However, there have been few studies that incorporate rectangular liquid channels in a PCM battery module composed of a high number of cylindrical cells. In this work, a new hybrid cooling system comprised of thirty cylindrical lithium-ion batteries (18650) combined with phase change material and a cooling channel was developed. The novelty of the study lies in the fact that (i) the battery module is designed to have a single inlet and outlet and is bifurcated at the inlet side to improve the symmetrical cooling of the entire battery module. (ii) This symmetrical cooling enhances temperature uniformity among battery cells, lowers maximum cell temperature, and delays PCM melting, allowing the PCM to absorb more heat from the batteries. (iii) In comparison to other complex hybrid cooling systems, the channels in this module may be easily manufactured, lowering the cost of battery module production. Insights into the influence of liquid channels can be best analyzed by extracting temperature and melted fraction data of phase change material. The proposed cooling system was shown to be capable of keeping the batteries' temperature below the optimal operating temperature at four different discharge rates (1C, 2C, 3C, and 4C). The proposed hybrid cooling system demonstrated to operate under harsh operating circumstances while yet keeping the battery at a safe temperature. At a mass flow rate of 0.001 kg/s and an inlet temperature of 30 °C, a maximum temperature and maximum temperature difference of 37 °C and 1.69 °C, respectively, were obtained, which are below the optimum temperature of 40 °C and a temperature difference of 5 °C. A maximum temperature and maximum temperature difference of 37 °C and 1.69 °C respectively were obtained at a water inlet temperature of 30 °C, making it the preferred inlet temperature.