Effect of copper metal foam proportion on heat transfer enhancement in the melting process of phase change materials

Phase change materials can overcome the low energy density and utilisation efficiency of solar energy. However, the low thermal conductivity of phase change materials significantly affects the thermal efficiency of solar devices; thus, improving the thermal conductivity of phase change materials has been the focus of many recent studies. Using paraffin wax and copper metal foam, copper metal foam composite phase change materials were prepared in this study. The effect of the copper metal foam proportion on heat transfer enhancement in the melting process of phase change materials was analysed using visualisation heat storage experimental equipment. The integrated heat transfer coefficient of the copper metal foam composite phase change materials was obtained. The experimental results showed that as the copper metal foam proportion increased from 0% to 2.13%, the melting time of the copper metal foam composite phase change materials decreased from 901 s to 791 s, and the heat storage rate and integrated heat transfer coefficient increased from 21.81 J/s to 25.08 J/s and 1.26 W/(m K) to 4.16 W/(m K), respectively. The heat storage capacity first increased and then decreased. The minimum temperature gradient of 5.2 K was reached when the copper metal foam proportion was 2.13%. More important, natural convection is the major heat transfer mechanism in the melting process of composite phase change materials with a low copper metal foam proportion; heat conduction plays a primary role in the melting process of composite phase change materials with a high copper metal foam proportion. The best heat storage and heat storage rate for copper metal foam composite phase change materials were 20260.49 J and 24.38 J/s, respectively, achieved with a copper metal foam proportion of 1.28%.