Structural Design And Heat Storage Performance Study For The Heat Storage Layer Of Solar Chimney Power Plant System

In this paper, the theoretical studies is carried out to the heat storage layer of the solar chimney power plant system with vertical collector. Paraffin octadecane is selected as filling material of the storage layer by considering the actual operating environment and selection principle of phase change material.Based on the structural mechanics indeterminate problems and the elasticity rectangular plate bending theory, the strength check for the rectangular vertical thermal storage devices proposed and designed is carried out. The results show that the actual floor stress of the structure designed is in allowable range of stress, while the side stress is beyond the allowable stress. In order to enhance the stability of the structure and improve the thermal efficiency, the metal separators are used in the thermal storage box. By calculation, the internal separators spacing is maintained at least 0.29m to make the device satisfy the force conditions under the maximum allowable stress.The temperature method model and enthalpy method model are analyzed and compared. The flow and heat transfer process of weak national convection are considered when the mathematical model are established. The temperature change rules and temperature field with the phase change of paraffin calculated by numerical calculation are compared with experimental results to verify the correctness of the numerical calculation method. The temperature variation of the phase change process can be obtained by numerical calculation method.According to heat transfer theory and hydromechanics, the physical and mathematical models of the heat storage device are established in this thesis. The temperature field and distribution of liquid rate are obtained by the method in which heat storage/exothermic process of the heat storage device in numerical simulation are studied by using CFD numerical simulation software. The results show that the natural convection can significantly improve the rate of paraffin phase change, and the natural convection strengthens melting process more obviously than solidification process. Observing the phase interface, there is an obvious interface tilt phenomenon in the melting process, this is due to the high temperature liquid paraffin flowing to the upper part.The phase change process in the heat storage device with different separator spacing(0.5m,0.25m,0.17m,0.125m) are analyzed. The results show:in the melting process, the phase change time is decreasing as descending parabolic with the increase of the separator numbers. It illustrates that the impact of natural convection on the heat storage capacity is related to the size of the natural convection space, in addition to gravity. The isotherms near copper plates incline due to the natural convection during melting, the paraffin melting effect below copper plates is significantly better than which is above copper plates. In the solidification process, the phase change time changes linearly with the number of separators. The isotherms near the copper plates is symmetrical approximately during solidification. Considering heat transfer rate and heat storage capacity, the optimal number of separators is obtained.