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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. • Alkane binary mixture is used to compensate for elevated melting intervals. • Metal foam enhances heat transfer of alkane binary mixture. • Molecular dynamics simulations predict the density and melting interval. • A coupling model of ocean thermal engine systems is proposed. • Factors influencing energy-storage performance are revealed. [ABSTRACT FROM AUTHOR]

Two polymers and five metal pairs were tested at six low temperature points and three constant load speeds. The tribological properties were determined by joint iterative coupling of the temperature, load and friction velocity value. Molecular dynamics simulation was used to study the micro-tribological properties of friction pairs at the atomic scale. The macro-tribological performance test results were similar to the results of the molecular dynamics simulation and exhibited the same trend. Two profound hypothermia points were predicted. The evolution of the tribological mechanism and properties of the polymer interface under different working conditions at low temperature were revealed on the macroscopic and atomic scales. [Display omitted] • A friction mechanism researching method based on a combination of macro and micro research was developed. • The macroscopic and microscopic tribological evolution rules of a polymer interface at low temperature were found. • The simulation was applicable to predicting polymer materials' tribological properties and explaining the test phenomena. • This method can be used for researches under harsher conditions and more extreme environments. [ABSTRACT FROM AUTHOR]