Analysis Of Heat Transfer Characteristics Of Phase Change Heat Storage System Based On Kriging Agent Model

In recent years,thermal energy storage(TES)has made great progress in the utilization of high-efficiency thermal energy,and has been widely used in engineering practice,solving the contradiction between energy supply and demand.With the increasing position of renewable energy in thermal energy system,the importance of TES has increased dramatically.In the current way of heat storage,latent energy storage technology has attracted great attention of researchers due to its remarkable advantages of energy saving and high energy density.Compared with the sensible heat energy storage system,the weight and volume of the latent heat energy storage system are smaller,which makes the cost of its application in engineering practice relatively low.But almost all pure phase change materials have the disadvantage of low thermal conductivity.Therefore,one of the main problems is to improve the thermal conductivity of PCM and the heat transfer efficiency of PCM.In the field of renewable energy utilization,latent heat storage system has become the focus of future research because of its low cost and controllable temperature.Therefore,the research of improving the performance of phase change materials and the optimization design of latent heat storage unit have great application value.In this thesis,based on Kriging agent model,the influence of phase change heat storage model structure on the thermal performance of the system was studied.Firstly,the mathematical principle of Kriging agent model and the error calculation method of one method cross validation were introduced,as the basis of the feasibility and calculation accuracy of the scheme combining the mathematical method with the heat storage model.In this thesis,based on the ring fin structure of the heat exchange pipe in the heat storage system,several cylindrical holes in the fins were made to improve the convective heat transfer effect.The location and quantity parameters of the internal cylindrical holes were optimized,and a six factor three level model was established.18 representative sample models were established by orthogonal experimental design,and 729 global optimization models of surface response were obtained based on Kriging method.Then the structure,number and location parameters of cylindrical pores were studied,and the influence mechanism of flow and heat transfer in the process of phase change heat storage was analyzed.It was found that the location of columnar holes near the adiabatic side is conducive to fluid mixing,but the number of columnar holes should not be too much,otherwise the positive influence of the convective heat transfer enhancement caused by columnar holes on the phase transition process is not enough to make up for the negative influence brought by the loss of thermal conductivity volume.Morever,In order to compensate the influence of columnar pore structure on the heat transfer volume of the fin,a boss structure with the same number and shape as the columnar pore structure was placed under the annular fin,and a three-factor and three-level heat storage model was established.It was indicated that boss structures can change the flow direction of fluid and accelerate the flow cycle in the system.The flow heat transfer effect in the system was enhanced in the presence of boss structures,and the model structure of the heat storage system with the optimal thermal performance was obtained.On this basis,the influences of the inlet velocity and temperature parameters of the heat transfer pipeline on the thermal performance of the phase change heat storage system were studied.