Composited phase change material with hierarchical metal foam for efficient thermal energy management

The composited phase change material (CPCM) with highly-conductive supporting foam material is promising in thermal energy management, which overcomes the disadvantages of low heat conduction capacity and possible liquid-phase leakage for organic PCMs, i.e. paraffin wax (PW). However, its energy storage efficiency (ESE) is not fully represented by the composite thermal conductivity. Practically, the phase change efficiency is mainly dominated by the coupling effect of heat conduction and natural convection, which is strongly related to the structural configuration of composite. In the present study, a simple and feasible hierarchical metal foam (HMF) structured by adding interior fins inside each pore is produced by shrinking Voronoi tessellations to achieve precisely tunable microstructure and porosity. Then the PW is integrated with the HMF to form an enhanced PW/HMF composite system. The hierarchical CPCM’s melting mechanism and energy storage behavior is studied under the condition of bottom heating through a numerical model, which is validated by comparing to the melting experiment. Subsequently, the influence of hierarchical topology representing by various fin sizes is quantitatively investigated on heat transfer behavior governed by the nature convection and heat conduction and the composite’s ESE denoting the amount of stored energy per unit melting time is assessed. To reasonably describe the composite’s ESE, a performance map related to different hierarchical topologies is provided to guide the design and application of the PW/HMF composite under the conditions that the foam porosity is different or same.