The Numerical Analysis Of Flow And Thermal Characteristics Of Graphite Foam

The graphite foam is a new kind of material with low density, high thermal conductivity, heat-resistant, erode-resistant and so on . Compared with other ordinary heat conductivity materials, it can fit the requirement of technological development better in aeronautics and space, automobile, military sector, communication and information fields, etc. So, the studying of its properties and production process have gradually become a hot spot.The studying about the graphite foam almost focus on the preparation. Many scholars have done a lot of research about flow, conductivity and convection characteristics of foam matericals by using theoretical, experimental and numerical approach and some fair complete theories and equations have been developed, but few were about graphite foam. So, this paper analysis the flow, conductivity and convection characteristics of graphite foam by numerical method deeply. And some conclusion and equtions are deduced based on the existing theories and equtions.This paper begins with several geometrical models of graphite foam using for its properties analysis, such as void model, solid model and porous model for conductivity, all of which are produced by VBA program using the macro files of CAD. The use of VBA and macro files of CAD facilitates the establishment of those models.For the aspect of flow character, this paper calculates the velocity and press field about some different models at varies boundary conditions. Then Based on the Darcy's Law as well as following researches, the inner press degree of foams is discussed. Finally, the number or equation of permeability number or Forchheimer number is got. As for heat transfer, after analysis of relationship between NuW and PeW , it is discovered that the permeability should meet that PeW<20 to make the convection use of graphite foam more economical.After the analysis of graphite foam's bulk conductivity, this paper proves that high conductivity and high convection are the major prerequisites of high bulk conductivity. At first, the temperature field of different models at varies boundary conditions is got based on the practical application of graphite foam material. The prime factors that influenceλe of graphite foam are discussed here. Then, with the combination of Hadley semi-empirical equation, the equation of bulk conductivityλe of porous material is got when the heat condcution of the fluid inside of porous material is considered . Finally, based on the analysis of convection , a brief discussion is made about howλe changes with the change of velocity of the fluid and porosity when convection is considered.