Role of partial and gradient filling strategies of copper foam on latent thermal energy storage: An experimental study

Low thermal conductivity of most phase change materials (PCMs) limits the practical application of latent thermal energy storage. This study aims to investigate the role of the partial and gradient filling strategies of copper foam on the heat transfer characteristic of latent thermal energy storage. A visual test rig was built to capture the evolution of the melting front over time. An infrared camera and T-type thermocouples measured the temperature fields and temperature profiles at specific points, respectively. The melting rate, temperature distribution and storage efficiency were investigated and analyzed in detail. The melting rate of PCM first increases and then decreases with the increase of filling ratio, and reaches the maximum value when the filling ratio is 5/6. The application of partial filling strategy reduces the maximum temperature difference of PCM and enhances the stability of the system. In the application of gradient filling strategy, copper foam with larger porosity should be arranged close to the heating wall or above the cavity. Partial and gradient strategy can increase the melting rate of PCM by reducing or maintaining the filling quantity of metal foam, which is of great significance for the practical application of metal foam in latent energy storage.