Thermal Transport in Metallic Porous Media

Abstract

Using porous media to extend the heat transfer area, improve effective thermal conductivity, mix fluid flow and thus enhance heat transfer is an enduring theme in the field of thermal fluid science. According to the internal connection of neighbouring pore elements, porous media can be classified as the consolidated and the unconsolidated. For thermal purposes, the consolidated porous medium is more attractive as its thermal contact resistance is considerably lower. Especially with the development of co-sintering technique, the consolidated porous medium made of metal, particularly the metallic porous medium, gradually exhibits excellent thermal performance because of many unique advantages such as low relative density, high strength, high surface area per unit volume, high solid thermal conductivity, and good flow-mixing capability (Xu et al., 2011b). It may be used in many practical applications for heat transfer enhancement, such as catalyst supports, filters, biomedical implants, heat shield devices for space vehicles, novel compact heat exchangers, and heat sinks, et al. (Banhart, 2011; Xu et al., 2011a, 2011b, 2011c). The metallic porous medium to be introduced in this chapter is metallic foam with cellular micro-structure (porosity greater than 85%). It shows great potential in the areas of acoustics, mechanics, electricity, fluid dynamics and thermal science, especially as an important porous material for thermal aspect. Principally, metallic foam is classified into open-cell foam and close-cell foam according to the morphology of pore element. Close-cell metallic foams are suitable for thermal insulation, whereas open-cell metallic foams are often used for heat transfer enhancement. Open-cell metallic foam is only discussed for thermal performance. Figure 1(a) and 1(b) show the real structure of copper metallic foam