Enhanced Phase Change Storage Simulation Research Of Nano-composite（Cu-H₂O） Phase Change Material

With the development of global economy, the shortage of resources, energy consumption is so huge that the problem of environment pollution and ecological pollution are perplexing the development of world economic and social sustainability. The rapid consumption of fossil fuels and the resulting of environmental pollution have become a difficult problem for the government and researchers faced. At present, the use of energy efficient, clean and has become a hot topic of concern to the industry in general. Energy storage is the indirect form, the energy shifts in time and space, using the method of the broad field of application, clean and efficient. Because the energy load user instability and energy is not easy storage, in order to improve energy utilization efficiency, phase change energy storage technology is widely used in energy storage technology.Phase change energy storage technology, can be divided into the process of energy storage and energy taking process, namely:the solidification and melting of two processes. In the two process, the energy transfer process can be described as:1:convection cooling solidification process before the low temperature side heat transfer with phase change material, so that the phase change heat cooling fluid to produce phase change, followed by heat conduction and solid phase change materials and energy transfer occurred, and the phase change material and the state of convective heat transfer the energy transfer, until the whole to solid phase change material, complete the process of energy storage;2:melting process:the high temperature side and the solid phase change materials with heat conducting form to transfer energy, solid phase change materials endothermic melting, followed by convective heat transfer form of energy transfer, and become the hot form of energy transfer between phase change material and solid phase transformation the material liquid for convection, until the whole into liquid phase change materials.Although the phase change material (phase change materials, PCMs) has the advantages of large energy storage, small volume, stable phase change temperature, but its main drawback is that, most of the thermal conductivity of phase change materials is very low, less than1W/(m· K). The transformation system with high performance is often in a small temperature difference (<20℃) condition, these two factors lead to the efficiency of heat transfer with phase change energy storage process is low, and the energy release process takes a long time storage.In view of the above problems, the researchers proposed many suitable for lifting energy storage system storage efficient way. In this paper, based on existing research, we selected Cu nanoparticles as a heat booster, H2O as phase change liquid, the characteristics of phase change materials, based on the FLUENT software. The Cu nanoparticles with different mass fraction of adding5%,10%,15%of the parameters of the model, gets the change condition of the optimization each addition of storage cold thickness and melting rate.The results showed that, in the process of cold storage, ice thickness reaches0.06m. cold storage efficiency of nano-composite phase change material with different mass fraction are all the best. After cold storage rate began to decrease with the increase of the thickness. At the same time, according to the amount of different mass fractions (5%,10%,15%), cold storage efficiency increase with the amount of nanoparticle added. According to the point of, different mass fraction(5%,10%,15%) of the storage efficiency increased by21.3%,38.7%,50.2%respectively.The melting process, according to the change of nanoparticles on the thermal conductivity of phase change materials and thermal diffusion coefficient, mass fraction of5%,10%,15%of nano-particle phase change materials, the melting rate were increased by14.3%,29.6%and43.5%. With the increase of liquid phase volume, the melting rate gradually increased. The melting process is dominated by natural convection. Natural convection phase transition area from the right wall heating up circulation to the left phase change interface, resulting in part is larger than the lower part of heat, so the solid-liquid phase change interface forms a ladder shape. In the circulation of the role, solid phase change material sinks on the solid-liquid interface, forming close contact melting, so that the existence of natural convection in a strong liquid solid interface, thus melting rate is greater than the solidification rate.