Research On Characterization Of Heat Transfer/Storage Characteristics Of Porous Skeleton Structure Composite Phase-change Material

Porous Skeleton Structure Composite Phase-change Material is an important carrier for the realization of phase change energy storage.It has many advantages,such as not easy to leak and stable performance.The establishment of scientific and effective characterization methods of composite phase change materials can provide favorable conditions for their large-scale application.According to the microstructure characteristics of porous framework composite phase change materials,three-dimensional simplified models of closed and through-hole are established,and the heat transfer model is established by using the sensible heat capacity method.Using C + + language,the program of solving discrete equation is written,and the program is optimized by block solving and multigrid technology.According to the numerical simulation results,the influence of different simplified models and the volume fraction of phase change materials on the non-equilibrium heat transfer process is studied.On this basis,the feasibility of using two temperature model to describe the non-equilibrium heat transfer in porous framework composite phase change materials is analyzed.The dimensionless coupling factors affecting the heat transfer between porous framework and phase change materials are proposed.The influence of different structural models and volume fraction of phase change materials on dimensionless coupling factors is discussed.The results show that:(1)The temperature difference between porous framework material and phase change material in the process of heat transfer reflects the degree of non-equilibrium heat transfer of composite phase change material.The maximum temperature difference in the closed hole model is less than the maximum temperature difference in the through hole model engraved at the same time,and the time that the temperature difference in the closed hole model drops to the standard in the same dimension is less than the corresponding time in the through hole model.The larger the volume fraction of phase change material is,the smaller the temperaturedifference of the through-hole model in the early stage of heat transfer is.With the passage of time,the larger the temperature drop rate of the model with the smaller volume fraction of phase change material is,and the shorter the time when the temperature drop below the standard is.(2)By solving the effective thermal conductivity of the three-dimensional model and taking it as the thermal conductivity of the skeleton material in the two temperature model,this paper studies the rationality of the two temperature model to describe the non-equilibrium heat transfer process of composite phase change material,and draws the following conclusions: in different structural models,with the increase of the through-hole area fraction,the corresponding value of dimensionless coupling factor is smaller;in the model with the larger volume fraction of phase change material,the value of dimensionless coupling factor is smaller Compared with the heat transfer process of composite phase change material described by effective thermal conductivity,the non-equilibrium heat transfer process of composite phase change material solved by double temperature model is more practical.This study can provide theoretical support for the establishment of measurement methods of heat transfer and storage characteristics of porous framework composite phase change materials in the future.