Role of pin fin-metal foam composite structure in improving solidification: Performance evaluation

Cold storage technology in air conditioning systems makes an important contribution to shifting peak load of electricity. How to break through the limitation of low thermal conductivity for cold storage medium so as to improve the energy charging/discharging efficiency is predominantly concerned. An experimental and numerical study on the solidification of phase change material (PCM) saturated in a novel pin fin-foam composite was carried out. Particular concerns were placed on the mass distribution of pin fins and metal foam for a given copper mass towards maximizing the solidification rate. To address this issue, a three-dimensional numerical model was built and verified by comparing with experimental measurements on solidification front evolution and temperatures at both PCM and fins. The variations in phase interface evaluation, solidification fraction, temperature field, and the cold storage capacity during ice storage were analyzed. Results demonstrated that the fin-foam composite outperformed the competing structures of metal foam or pin fin, favoring a significant improvement in PCM solidification. A 40% fins and 60% metal foam combination was recommended towards maximizing solidification rate for engineering applications. When the target solidification fraction was 90% for operation, the fin-foam cold storage tank had the longest investment payback period and the largest 20-year total profit among the four structures among the four cases (pure PCM, pin fin, metal foam, and fin-foam composite).