Analysis Of Thermal Conductive Characteristics Of Non-homogeneity Porous Foam

Porous foam is a new functional material formed by the solid skeleton and massivepores, and has the excellent features of high surface area, low density. With the rapiddevelopment of aerospace industry, the auto industry and information industry, thematerial needed shall be have excellent performances of thermal, high mechanicalstrength, shock absorption, electromagnetic shielding and so on. Compared withconventional metal materials, porous foam can meet these needs better and have alreadyshown the application prospect in national defense, energy, aviation and military area.So to study the performances of porous foam is important.Due to the pores, the affecting factors of material properties are more complicate.Prior studies are based on periodic geometric structure. The most of actual porous foamsare heterogeneity, that means pores size and distributions are random and non-periodic,and this paper aims at non-periodic geometric structure. The affection of heterogeneitystructure to the conduction of porous foam has been studied through numericalsimulation. The main research content includes:Two and three dimension models are established based on the random and non-periodic feature, random variables are introduced.Two dimension models uses eccentricfactor and aperture disturbance factor to show the variation of pore location and size.Three dimension models uses average aperture and deviation to show the variation ofpore size.Numerical simulation has been done by ANSYS and effective thermal conductivityof the models is obtained. Uniformity stands for the randomness of the pore structureand both uniformity and porosity are the pore structure parameter. Simulation resultssuggest uniformity decreasing leads to effective thermal conductivity decreasing. Bothuniformity and porosity affect effective thermal conductivity. Pore location and sizerandomness can cause the variation of effective thermal conductivity. This paper thinksthat random pore position not only brought about changes in the uniformity, at the sametime, the merger of pores can change model’s porosity and pore size random variationcan change uniformity of model. From the simulations results of these random models,it is point that the relative effective thermal conductivity of foam material can beexpressed as power function of porosity and uniformity.We also tested the effective thermal conductivity of three porous foams. The results suggest that effective thermal conductivity increases as temperature rising.