Melting and solidification performance of latent heat thermal energy storage system under flip condition

Latent heat storage technology has made significant contributions to solving the problem of unstable renewable energy supply. Related research indicates that phase change devices are essential for the stability of spacecraft temperature control systems. However, phase change material (PCM) has low thermal conductivity, which reduces device thermal storage and release efficiency. Moreover, the PCM heat transfer performance is further affected by movements such as attitude adjustment during the launch and operation of spacecraft. This paper adopted active heat transfer enhancement technology to enhance uniformity and rate of heat transfer in latent heat thermal energy storage (LHTES) unit. A new method is presented on flipping LHTES unit at appropriate stages of the phase change process, namely flipping enhancement technology. This method effectively uses the benefits of natural convection to enhance heat transfer, reducing the storage and release time of LHTES systems. A physical model was established building upon verification with data in literature, and the effect of flipping under different phase transition fractions on melting and solidification performance within the square cavity was discussed through numerical simulation. Further analysis was conducted on factors including phase transition fraction, phase interface, temperature interface distribution, velocity interface distribution, and heat storage capacity. Finally, the response surface methodology (RSM) was adopted to analyze and determine the optimal flipping phase transition fraction. The research results indicate that flipping improves the heat transfer efficiency of LHTES. Flipping significantly enhances heat transfer 3–5 times during melting compared to solidification process. As the phase transition fraction increases, the complete melting/solidification time demonstrates a trend of decline followed by an increase. Through single factor analysis, the optimal flipping liquid fraction is 51.65 % during the melting process, leading to a substantial decrease in complete melting time by 25.71 %. Based on this, the optimal phase transition fraction combination of melting first and then solidification was explored, which shortened the melting-solidification full cycle time by 12.96 %. This study investigates the melting/solidification performance of LHTES unit under flip conditions, which guides the design of phase change thermal control devices and contributes to the field of spacecraft thermal management.