Effect of metal foam on improving solid–liquid phase change in a multi-channel thermal storage tank

Abstract

Latent heat thermal storage (LHTS) system is a vital way to recover waste heat for energy saving. However, phase change materials (PCMs) with low thermal conductivity severely limit the energy storage efficiency. A novel LHTS tank with multi-channels filled with metal foams is designed to improve the overall heat storage efficiency. Further, a three-dimensional phase transition model is developed, with particular concerns paid on the filling pattern of metal foam in HTF, PCM, and both. The numerical model can better reveal the synergistically enhanced heat transfer and conduction mechanism of heat transfer fluid (HTF) and PCM with metal foam. The numerical model is verified with the existing experimental data, and a satisfactory agreement is obtained. Four filling methods are designed, in which the porosity and pore density of metal foam is 0.93 and 15 pore per inch, respectively. Compared with the non porous tank, the phase transition time can be reduced by 23.7% for PCM filled with metal foam; while filling HTF with metal foam reduces the melting time by 58.3%. The synergized effect of filling both reduces melting time by 77.6%. The heat flow into PCM is increased when metal foam is in HTF. Further, when metal foam is in PCM, the temperature uniformity of PCM is augmented and its phase transition isothermal duration is prolonged. The assessment options can provide scientific design guidance for improving the thermal storage efficiency of LHTS tank.