Analysis Of Heat Transfer Performance Of High Temperature Phase Change Capsule Heat Storage

With the rapid economic development of various countries,non-renewable energy sources are increasingly in short supply.Solar energy is the most extensive and clean renewable energy,but the sun is unstable and intermittent,which makes the use of solar energy more difficult.Therefore,it is necessary to store the heat of solar radiation to make the solar thermal power generation system continue to operate.Phase change materials can achieve thermal energy storage,but phase change materials also have some disadvantages.Phase change capsules can solve the problems of corrosion and leakage of phase change materials,which makes phase change capsules a hotspot in research,so it has great practical significance for the research of high temperature phase change capsule heat storage.With the support of The National Natural Science Foundation of China(No.51906228),this paper studied the heat storage performance of the high-temperature phase change capsule containing air and the heat storage characteristics of the high-temperature phase change capsule.The main research work and results are as follows:(1)The physical and mathematical models of the high-temperature phase-change capsule and the high-temperature phase-change capsule heat storage are established to verify the correctness of the model,and the grid assessment is carried out.(2)The heat storage performance of high-temperature phase-change capsules was numerically simulated,and the effects of different wall temperatures of the phase-change capsules and different void ratios in the high-temperature phase-change capsules on the melting process of the phase-change capsules were studied.The results show that the time to completely melt the phase change capsule decreases with increasing wall temperature;the time to completely melt the phase change material decreases with increasing porosity.(3)The effects of different wall thicknesses and diameters of high temperature phase change capsules on the complete melting time of phase change materials were studied.It was found that when the thickness was increased from 1 mm to 2 mm,the time for the phase change material to completely melt increased by about 11.8%;as the diameter of the high temperature phase change capsule increased,the time for the phase change material to completely melt increased.(4)The effects of the addition of nanomaterials and the different shell materials(thermal conductivity)of the phase change capsule on the heat storage performance of the high temperature phase change capsule were studied.As a result,it was found that with the addition of nanomaterials,the melting rate of the high-temperature phase change capsules was accelerated,and the time for complete melting was reduced;as the thermal conductivity of the shell material increased,the time for complete melting of the phase change material was shortened.(5)The numerical simulation of high temperature phase change capsule heat storage was carried out,and the effects of different inlet velocity,different inlet temperature,different shell materials of phase change capsule and different combinations of phase change materials on the performance of heat storage were studied.The results showed that the melting time of 0.005m/s and 0.01m/s decreased by 13.24% and 34.93%,respectively,compared with 0.003m/s.Compared with the inlet temperature of 1007 K,the melting time of 1017 K and 1027 K PCMS was reduced by 12.78% and 24.32% respectively.As the thermal conductivity of the shell increases,the time for complete melting of the PCM in the reservoir system decreases.The heat storage time of the combined phase change material heat storage is significantly shortened,compared with the use of a phase change material,the time is shortened by 21.75%.When the capsule contained air,the complete melting time of the PCM was reduced by 15.58%.