Experimental investigation of the comprehensive heat transfer performance of PCMs filled with CMF in a heat storage device

•A greater proportion of copper metal foam (CMF) can enhance the heat transfer of paraffin wax and reduce the temperature gradient.•A theoretical model was built to calculate the comprehensive heat transfer coefficient of composite PCMs and to determine the intensity change of heat conduction and natural convection of PCMs with different CMF proportions.•Melting time and heat storage capacity of CMF composite PCMs first increased and then decreased with increasing CMF proportion.•Heat storage rate and comprehensive heat transfer coefficient first decreased and then increased with increasing CMF proportion.•Composite PCMs with a CMF proportion of 0.86% exhibit the best heat storage performance.