Mist cooling lithium–ion battery thermal management system for hybrid electric vehicles

Battery Thermal Management System (BTSM) is essential for maintaining optimal operation conditions for hybrid electric vehicles (HEVs) and electric vehicles (EVs). This study aimed to propose an innovative impinging jet cooling BTMS for HEVs using mist cooling. The dilute mist completely evaporated to avoid the risk of external circuit failure or corrosion that could result from surface wetting. Impinging experiments were performed under the conditions where inflow air temperature, Ta,in, was 21.2 °C ≤ Ta,in ≤ 31.0 °C and initial humidity, φ, was 50.9 %RH ≤ φ ≤ 96.0 %RH. It was found that the target plate was cooled down by up to 0.8 K without surface wetting by adding 5.5 mg/s water mist to the air. Numerical analyses were performed under conditions ranging from 21.2 °C ≤ Ta,in ≤ 31.0 °C and 0.0 %RH ≤ φ ≤ 100.0 %RH. The results and discussion highlight the importance of the critical initial humidity, φcritical: the complete evaporative threshold. Deviation between the experimental and numerical results at a fixed inflow air temperature, Δφ, was −1.9 %RH ≤ Δφ ≤ 3.0 %RH. Δφ was within the range of measurement uncertainty U(φ) = 4.0 %RH. Thus, the experimental and numerical results were consistent within the experimental measurement uncertainty. As a result, φcritical tends to be high in the case of high inflow temperature. The mist cooling is a viable way of BTMS for HEVs without surface wetting due to its large cooling capacity that results in a 7.4 K cooling effect in a hot environment.