Simulative Study On The Heat Storage Performance And Design Of The Solar Hot Water System

With the development of economy and society, energy crisis have already become a problems faced to us, As a renewable clean energy, the solar energy has a broad application prospects in the current tight supply and increasing demand. But unfortunately, how to store the solar energy becomes a big obstacle in its development. Latent heat thermal energy storage(LHTES), can storage energy by Change the phase of phase change material, which can be used to solve the nonconformity problem on supply and demand time of solar energy. Due to the merits of high-density energy storage, easy to match and easy to control, the research and application of Latent heat thermal energy storage technique has drawn more attention.The research based on a new kind of solar energy system with phase change material. The focal point of this text will simulation study heat transfer of the hot water storage tank. The process of phase change accompanied with cconduction and convection, Which make the solution to the Problem of heat transfer with Phase change complicated, which in most case we have to turn to numerical simulation to solve. In this Paper, the software Fluent was employed to simulate the impact factors and the ways to enhance heat transfer in the proeess of phase change. The following topics are studied:(1) The auther set up physical and mathematical model of phase change ball which was used for thermal storage, and simulated the solidificaltion and melting process of it under different cliff side temperature. The temperature filed is obtained and phase change interface position changed with time is also calculated.(2) Mathematical model of the shell and tube LHTES system is developed using the enthalpy method. By using solidification/melting models of FLUENT software, the melting process of paraffin in a shell-tube is numerically simulated. Considering the nature convection in the liquid phase and the hot media coupled with the unit, temperature field is obtained and phase change interface position changing with time is still calculated.(3)Add fins into the system of thermal storage with Phase change, in order to increase the speed of heat storing. Numerical simulations are carried out to study the effects of fin pitch,fin length, fin Thickness and fluid temperature on charging performances of the LHTES system.(4) Designing a new hot water storage tank using for solar water heating system. Compared with existing hot-water heater, it has advantages of Small size, low cost, low operating costs. It will has great development potential.