flow condensation heat transfer of r134a inside the tubes filled with hydrophilic metal foam: an experimental approach

In this study, the effect of metal foam surface wettability on flow condensation heat transfer inside tubes is investigated. r134a is used as working fluid. the diameter and the length of the tube are 8mm and 40cm, respectively. metal foams are 20ppi, and the vapor mass flow rate ranges from 75 to 125kg/m2s. the impact of vapor quality, mass flow rate and metal foam surface wettability on flow condensation heat transfer are analyzed. results show that in high vapor quality, more than 0.5, the heat transfer coefficient in the hydrophilic metal foam filled tube is increased by 2-22% compared with that for the uncoated one. in contrast, for low vapor quality, heat transfer coefficient is decreased by 1-13%. as well, flow condensation heat transfer is improved when mass flux and vapor quality are increased in both hydrophilic and uncoated metal foam filled tubes.