Investigation on thermal management of AUVs battery packs via an innovative bionic ram liquid cooling design

Safety issues related to the thermal behavior of lithium-ion battery packs severely constrain the development of high-speed autonomous underwater vehicles (AUVs). To solve this problem, a novel adaptive speed-based ram liquid cooling strategy is proposed for regulating the temperature of high-speed AUV battery packs. A three-dimensional full-scale AUV battery pack cooling performance evaluation model based on electrochemical-thermal coupling was established, and the effects of flow channel shape, shark-fin inlet duct diameter, seawater ambient temperature, cruising speed, and angle of attack were comprehensively assessed. The key results show that the ram liquid cooling strategy serves as an effective thermal management technique for AUV battery packs, with its thermal performance matching the AUV cruising speed. Compared with uncooled packs, the maximum temperature of those with ram cooling decreased by 13.58 K at 5C discharge rate. The serpentine channel cooling scheme is superior to the other three (flat-plate channels, parallel channels and symmetric channels) in simultaneously optimizing both the maximum temperature and temperature uniformity, resulting in only a 0.58% AUV drag force increase. Additionally, the maximum battery pack temperature improves gradually with increasing inlet diameter, but the improvement diminishes and tends to saturate when the diameter exceeds 10 mm. The maximum temperature increment is proportional to seawater ambient temperature, and the AUV cruising angle of attack has a negligible impact on the peak temperature of battery modules. The proposed cooling strategy and research findings provide a reliable engineering design roadmap for high-speed AUV battery pack temperature control systems.