Computational study on hybrid air-PCM cooling inside lithium-ion battery packs with varying number of cells

Rising global pollution index, together with transportation vehicles as one of the major contributors, has prompted researchers to focus on clean and renewable sources of energy. Electric vehicles (EVs) with rechargeable lithium-ion battery offer a promising option to develop clean energy vehicles. However, in order to bring off an optimal performance, a specified temperature range must be chosen for the operation of these batteries. Here, we numerically investigated a battery thermal management system (BTMS) utilizing encapsulated phase change material (PCM) combined with forced convective air cooling using the coupled electrochemical-thermal modelling. Commercial SONY 18650 type lithium-ion cells were taken in two arrangements, namely, inline and staggered. PCM encapsulation of thickness 0–3 mm over the cells was used. Broadly, the influence of increasing cell number (N) on the cooling performance and thermal uniformity has been delineated at discharging rates of 1C, 2C and 5C. A scrupulous analysis of temperature and velocity distribution, cell temperature (average and maximum), and thermal uniformity plots have been reported. Typically, for N = 8, a significant reduction of ~33 K in average temperature was seen at 5C discharge rate and air inlet velocity of Uin = 0.2 m/s when only a thin layer (1 mm) of PCM is applied on the cells. Moreover, a simple predictive correlation is established for a priori estimation of the average and maximum cell temperature in the gamut of pertinent parameters. Lastly, for an optimization viewpoint, a comparative analysis of results is presented based on different location of PCM encapsulation.