A comprehensive investigation of autonomous underwater vehicle battery thermal management system using metal foam/paraffin composite

Electric autonomous underwater vehicles (AUVs) are facing more urgent battery thermal management (BTM) demands than electric cars, as their battery compartment design is constrained by limited volume, airtightness and impact loads. In this paper, a novel hybrid battery thermal management strategy of metal foam/paraffin composite combined with thermal bridges is proposed for the AUVs' BTM. A three-dimensional model considering the non-thermal equilibrium effect for AUVs' battery module was developed. Gradient PCMs and gradient foam porosity were introduced to improve the temperature and melting behaviors in various regions of AUVs' battery pack. The trade-off between performance and weight of metal foam/PCM composite on AUVs' battery thermal management was also quantitatively analyzed. The results showed that the temperature in the top region of the battery pack was higher than that in the bottom region due to the natural convection of the liquid PCM. The positive gradient porosity of metal foam has the advantages of large porosity increasing the heat storage and small porosity improving the thermal conductivity, both benefit to reduce the maximum temperature of the battery module. The positive gradient latent heat and melting point hybrid strategy of PCM demonstrates the best thermal management performance when compared with constant parameter cases, and the maximum temperature of battery modules is more sensitive to the melting point of PCM. When the metal foam/PCM composite was introduced, the weight of the battery module increased by 27.1%, while the maximum temperature and temperature difference of the battery module decreased by 44.27 K and 11.1 K, respectively. The safe working time of the battery module was extended by 105.7%, and the mass-energy density that can be utilized was increased by 61.9%. The findings can help AUVs to achieve the goals of high speed and long range.