Thermal and hydraulic characteristics of bubbly flow in a metallic-porous-media*

In the past decades, heat transfer and flow behavior in porous medium has attracted many researchers. Geometrical properties of high-porosity open-cell metallic foams possessing extremely high specific surface area and lots of randomly connected path inside the medium body can improve thermal performance of compact heat exchangers, especially in the two-phase bubbly flow. In this study, flow boiling in metal foam inserted channel is experimentally investigated with a focus on the bubbly flow regime. The channel of cross section 5 mm by 50 mm is used to study the effects of vertical-up flow. R245fa is selected as the working fluid and hot water is used as a heating source. Boiling heat transfer coefficient and pressure drop properties across different types of metallic foam structure are measured and discussed with the effects of the inlet vapor quality and the heat flux. In order to observe the bubble behavior through the metallic porous media, a visualization experiment is performed. The results addressed in this paper could be helpful to understand the flow boiling heat transfer mechanism inside the metallic porous media.