Research on coupling enhanced heat transfer with energy storage in ocean thermal engine systems

Underwater vehicles are generally supplemented and driven by ocean thermal engine systems (OTES), leveraging the large thermal-energy reserves via solid–liquid phase change materials (PCMs). However, the low thermal conductivity and high-pressure melting point migration of PCMs severely limit their energy-storage performance. In this study, alkane binary mixture PCMs and enhanced heat transfer structures were integrated into the OTES to increase the energy storage power. The melting point of pure n-hexadecane was reduced using a 5% mass fraction of n-octane. The density and melting interval of an alkane binary mixture PCM at different pressures were studied using molecular dynamics simulations. An OTES coupling model based on the enhanced heat-transfer theory of metal foams was developed. The minimum relative error in the model prediction of melting time was 1.13%. The effects of different precharge pressures, nominal volumes, and energy-storage strategies of the accumulator on the energy-storage process were investigated. The results indicate that a large nominal volume, precharge pressure, and energy-storage interval are beneficial for improving the energy storage power. For 5 L accumulator, the maximum power for single energy-storage strategy is 13.92 W, while multiple energy-storage strategy improves by 41.52% to 19.7 W.