Numerical Analysis Of Characteristics Of Couple Radiation And Conduction In 2D Porous Materials

Porous materials have good thermal and mechanical properties,so widely used in the field of heat transfer and solar energy harvesting.The phenomenon of energy transfer in porous media is ubiquitous in the field of engineering.And radiative heat transfer in porous materials cannot be neglected at high temperature.At present,the research on the heat transfer of porous media is mainly focused on the study of pure thermal conductivity.There are few studies on the radiation heat transfer.Most of the porous media radiation heat transfer studies is about the radiation properties of the porous media,and the heat transfer process of the porous medium research is quite rare.Therefore,the heat transfer characteristics of porous heat transfer in porous media are studied in this paper.In the paper,we proposing an effective discrete ordinate ray tracing(DORT)method to simulate radiative heat transfer in arbitrary porous materials at pore-level.The complicated pore structure is expressed with implicit geometry based on function expression,which facilitates the calculation of normal vector at interior material interfaces that is essential for the calculation of reflected radiative power.Discrete energy conservation equation method is applied to analyze couple heat transfer in porous media,and putting forward a formula to calculate the effective conductivity of couple heat transfer in porous media.we study the effective conductivity of periodic structure and random structure porous media,analyzing porosity,pore diameter,scale etc structural factors and temperature,emissivity,solid conductivity etc unstructural factors effect on effective conductivity.And we doing dimensionless analysis on couple radiative-conduction heat transfer in porous media,and proposing a dimensionless parameter,get dimensionless correlations that effective conductivity changes with dimensionless parameter.The dimensionless parameter contains factors such as temperature,emissivity,and conductivity,witch is an important parameter in the heat transfer process of porous materials.The results show that the higher temperature,the larger the effective conductivity.The larger the thermal conductivity,the greater effective conductivity.For the closedcell porous material,the larger porosity,the smaller effective conductivity.The larger pore size,the smaller effective conductivity.And the larger emissivity,the larger effective conductivity.For the open-cell porous material,the larger porosity,the larger effective conductivity.The larger emissivity,the smaller effective conductivity.Dimensionless analysis showed that: effective conductivity of closed-cell material changing with the dimensionless parameter have the minimum and saturation value.The effective conductivity of open-cell material along with the change of dimensionless parameter has the minimum,and effective conductivity increases linear sharply with dimensionless parameters.Finally,we based on theory quantitative analysis of effective conductivity of porous media,and the result is identical with the simulation results.