How can copper foam better promote the melting process of phase change materials

The low thermal conductivity of most phase change materials (PCMs) significantly limits the heat transfer rate, which is challenging for further application in thermal energy storage, energy saving of buildings, electronics cooling, etc. Here, we use the effective protection time of PCM heat sinks to represent the effect of copper foam on the melting behaviors of paraffin. Moreover, the effects of heat flux and copper foam filling ratio (beta) were discussed on the effective protection time, the quantified contribution of natural convection, and the melting fraction of paraffin. The results prove that a good match between the physical parameters of the PCM heat sink and the working parameters of electronic components is essential to make full use of the latent heat. By contrast, a mismatch of 10 degrees C in allowable temperature or 0.21 W cm-2 in heat flux can be eradicated by a full filling of copper foam in paraffin. Specifically, the copper foam extends the effective protection time by enhancing heat conduction at beta <= 60%, then it is further prolonged by improving the natural convection at beta>60%. The results are expected to guide the synergistic enhancement of heat conduction and natural convection inside PCMs filled with copper foams.