Dynamic volumetric forces-driven phase change behavior and gradient structure design of copper foam/paraffin CPCMs

Latent heat thermal energy storage system (LHTES) based on copper foam composed phase change materials (CPCMs) has great potential in regulating the thermal management of the electronic devices. When applied in the aerospace field, heat transfer performance of CPCMs can be affected the dynamic volumetric forces, significantly impacting the temperature control of the internal electronic devices. This paper experimentally and numerically assesses the heat transfer performance of the copper foam/paraffin CPCMs under volumetric forces. The direction of the equivalent gravitational acceleration was perpendicular to the heat flux direction by adjusting the tilt angle and rotation speed of the phase change unit. Three gravity conditions, of namely microgravity, constant gravity and supergravity, are introduced in this investigation. The supergravity significantly enhances liquid natural convection, while microgravity suppresses it, thereby slowing down the melting rate of CPCMs. The porosity of the copper foam is found to be able to shorten the total melting time of CPCMs and lower the temperature of the heat wall surface. The pore density of the copper foam exerts substantial influence on the solid-liquid phase interface evolution of CPCMs. The melting time of CPCM and the heat wall temperature decrease with the augment of the pore density of the copper foam. A non-uniform gradient phase change unit consisting the high porosity copper foam in the upper part and the low porosity copper foam in the bottom part is designed to enhance the heat transfer performance. The total melting time of CPCM in the gradient phase change unit is shortened by 6.7 %, and the heat storage rate is enhanced by 7 % under normal gravity. In conclusion, the research contributes to the LHTES application subjected to various dynamic volumetric forces.