Study On Enhanced Heat Transfer Of The Reticulated Fins To Solar Phase Change Heat Accumulators

Phase change heat storage technology has the advantages of stable heat storage and release temperature,large energy storage density,and easy control of phase change process,and has in-depth research value.Existing phase change heat accumulators face the problems of slow heat storage process and uneven temperature distribution of the heat accumulator during heat storage.In this paper,a new type of the reticulated fins heat accumulator is designed and developed,which has a simple structure compared with foam materials,increases the contact area between the phase change material and the fin,and then increases the heat transfer coefficient of the phase change material,which transmits heat faster and shortens the heat storage and release time.Moreover,the reticulated fins block the phase change material,which improves the erosion of the upper and lower phase change materials of the heat accumulator by natural convection,and the solidification and melting of the phase change materials in each region are more uniform.At the same time,ANSYS embedded software Fluent was used to numerically simulate the heat storage and release process of the reticulated fins heat accumulator,and the temperature field,solid-liquid phase cloud and liquid phase rate curve at different times of the heat storage and release process of the reticulated fins heat accumulator were obtained,and the influence of the structural parameters of the reticulated fins on the heat storage and release process of the heat accumulator was investigated through the analysis of the obtained cloud and curve chart.The influence of operating parameters on the heat storage and release process of the heat accumulator was investigated;On this basis,The structure of the reticulated fins heat accumulator is optimized and the numerical simulation analysis is carried out.With The increase of the radius R of the reticulated fins,the heat release time gradually decreased,while the heat storage time showed the phenomenon of first decreasing and then increasing.With The increase of longitudinal fin thickness c,the reticulated fins thicknessδand number of longitudinal fins N,the heat storage and release time decreased.the optimal structural parameters of the reticulated fins were R=33.5 mm,c=3 mm,δ=3 mm,N=8,and the shortest heat storage time was 8 086 s and the heat release time was 5 845 s.During the heat storage process,with the increase of the temperature T of the heat exchanger tube wall,the liquid phase rate value gradually increased,and the liquid phase rate value of the composite phase change material is greater than the liquid phase rate value of pure paraffin engraved at the same time,and the overall heat storage time was shortened.During the heat release process,with the increase of the temperature T of the heat exchange tube wall,the liquid phase rate value gradually increased,and the liquid phase rate value of the composite phase change material is greater than the liquid phase rate value of pure paraffin engraved at the same time,and the overall heat release time increased.Compared with pure paraffin,composite phase change materials have a shorter heat storage time and a longer heat release time.The structure of the reticulated fins is optimized in three ways,adding Y-shaped fins,center offset of heat exchanger tube and changing the fin installation angle.When the structural parameters of Y-shaped fins are s=28.5 mm,L=23 mm,c _Y=3 mm,N_Y=3,the minimum heat storage time is 6 084 s,and the heat release time is 4 947 s.When the center offset distance of the heat exchanger tube is e=18 mm,the shortest heat storage time is 5263 s and the heat release time is 10 273 s.When the installation angle is 75°,the minimum heat storage time is 10 500 s and the heat release time is 10 155 s.