Simulation And Optimization Of Heat Storage/Exothermic Process Of Longitudinal Finned Tube With Double Open Angle Based On Phase Change

Phase change heat storage is a technology for storing energy by absorbing or releasing heat in a phase change material during the ph ase change process.It has the advantages of large energy storage density,strong heat storage capacity and constant phase transition temperature,which can effectively alleviate the mismatch of time,location and intensity between energy supply and demand.Therefore,phase change heat storage technology has been widely used in many fields such as chemical industry,power energy,aerospace and building energy conservation,which has become an effective way to solve the energy crisis.The key factor of phase change thermal storage technology is phase change material.However,the thermal conductivity of phase change materials is relatively low,which results in unsatisfactory heat transfer effect,which limits the industrial application of phase change therma l storage technology.Thus,the strengthening problem of the phase change thermal storage technology has become a research hotspot in the field of energy applications.This influence of the finned tube structure on the performance of the thermal storage device was mainly studied.In this paper,paraffin wax is used as phase change heat storage material,and a new double open angle longitudinal fin tube structure is designed.The numerical simulation method was used to simulate the heat storage process and the heat release process by Fluent software.Both the effects of finless and straight fins on the storage/discharge performance and the influence of structural parameters and boundary conditions on the heat storage process were compared and discussed respectively.Through the analysis,the following conclusions are drawn:(1)The mechanism of the influence of fin structure on heat storage performance was studied.The results show that compared with the light pipe and the straight fins,the double-opening longitudinal fins designed in this paper have a complete melting time of 63.27% and 23.53% respectively in the process of heat storage.During the exothermic process,the paraffin solidification time was also shortened by 60.39% and 26.66%,respectively.At the same time,the heat storage and the efficiency of heat storage under these three working conditions were calculated and compared,and the heat transfer effect of the double-opening longitudinal fin structure was found to be the best one.(2)The effects of the number of fins,the angle of the fin opening angle,the thickness of the fin,the dimensionless height and the position of the fin opening angle on the heat storage performance were investigated,the results show that the number of fins is the main factor affecting the heat storage efficiency.It is found that when the working condition satisfies one of the following four conditions,the time required for the phase change material paraffin to melt is the shortest,that is,the fin opening angle ?=60°,the fin thickness ?=1mm,the dimensionless height ?=0.903 or the fin opening angle position s=6.67 mm.(3)The effects of other factors on heat storage efficiency was studied.It was found that the proper increase of the inlet flow rate and temperature o f the heat carrier can also shorten the melting time of the phase change material.When the temper ature of the heat carrier is 90?,the inlet flow rate is 0.8m/s,the effect is optimal.