Abstract: The stability, heat transfer efficiency and photothermal conversion efficiency optimization studies of solid-liquid phase change materials (PCMs) applied to water heaters were reviewed. Suggestions and prospects were proposed. The study shows that domestic and foreign research on the application of phase change materials in water heaters focuses on the improvement of the performance of thermal storage materials (thermal storage capacity, thermal conductivity, stability) and the application of the effect and efficiency enhancement, and the location of the material application is mostly found in the water tank, storage or collector of the water heater system, and the filler materials are mostly paraffin wax. The addition of solid-liquid phase change materials can significantly improve the performance of water heaters, shorten the heating time, and improve energy efficiency. However, as the application research rarely includes the application cost in the evaluation system, it is still necessary to further combine the application scenarios and economics of phase change materials to carry out a comprehensive multi-objective evaluation study, so as to promote the application and popularization of new materials in water heaters.

Key words: PCM, Water heater, Heat transfer efficiency, Performance coefficient, Photothermal conversion