多孔介质在高温相变蓄热中的强化换热

采用实验方法，验证了金属泡沫、膨胀石墨在高温蓄热系统中强化换热的作用。实验结果表明，在250～290℃之间，金属泡沫多孔材料能够提高纯硝酸钠的换热率2.1倍。由于多孔材料严重抑制了自然对流，在液相加热阶段，硝酸钠与多孔材料混合物的换热率不高于纯硝酸钠的一半。通过比较底部加热和顶部加热两种加热方式下蓄热系统的换热性能，进一步揭示了多孔材料对自然对流的影响。

Heat transfer enhancement of high temperature thermal energy storage using porous materials

Latent heat storage(LHS) can theoretically provide large heat storage density and significantly reduce the storage material volume by using the material’s fusion heat.Phase change materials(PCMs) commonly suffer from low thermal conductivities.The problem of low thermal conductivity is a major issue that needs to be addressed for high temperature thermal energy storage systems.Since porous materials have high thermal conductivities and high surface areas,they can be used to form composites with PCMs to significantly enhance heat transfer.In this paper,the feasibility of using metal foams and expanded graphite to enhance the heat transfer capability of PCMs in high temperature thermal energy storage systems is investigated.The results show that the porous material can improve the heat transfer rate of pure sodium nitrate of 2.1 times.Porous materials severely inhibited natural convection in the liquid phase heating stage,the heat transfer rate of the mixture of sodium nitrate and porous materials is not more than half of the pure sodium nitrate.By comparing the heat transfer performance of the bottom heating and the top heating of the heat storage system,this paper further reveals the porous material impact on the natural convection.