Numerical investigation of heat transfer improvement in a latent thermal energy storage system using a composite of phase change material and nanoparticles in a porous medium

In the present study, the flow field and heat transfer in an energy storage tank are simulated. The Phase Change Material (PCM) in the present study is paraffin, which is converted to a liquid phase by the introduction of a hightemperature fluid (80 degrees C) and then the cold fluid enters the flow-carrying tubes, causing the melt to freeze. In the freezing (discharge) phase, the heat released from it increases the temperature of the fluid. Tubes in tank configurations are also used in latent thermal energy storage, which also performs well in terms of heat transfer. In this research, the use of special geometry with special and practical boundary conditions in order to estimate the charging and discharging behavior of the process of melting and freezing nano-phase change materials in it, as well as the instantaneous examination of the temperature field, melting and freezing by using a computer code using the finite volume method, can distinguish the results of this research from other studies. The results of this research show that, the shape of the tube and storage tank is slightly different from the shell-tube type, in which the Heat Transfer Fluid (HTF) flows through the tubes and these tubes also pass through a PCM tank. The study of the effect of porosity coefficient of porous medium shows that the rate of phase changes in porous medium with porosity coefficient of 0.95 is more than porosity coefficient of 0.97. In addition, by adding nanoparticles to paraffin the melting process takes place in a short time. According to the results, the nanoparticles added to the PCM accelerate heat transfer while maintaining energy storage capacity.