Flow condensation in tube filled with annular metal foam

The tube with internally sintered annular metal foam layer is used to enhance the flow condensation heat transfer. The pressure drop and heat transfer of flow condensation for refrigerant R134a in the tube partially filled with annular metal foam are experimentally investigated to overcome the disadvantage of large pressure drop for tubes fully filled with metal foam. The tube wall temperatures are measured with thermal couples to determine the heat transfer coefficient. The effects of mass flux and vapor quality of two-phase fluid on the pressure drop and heat transfer coefficient are analyzed accordingly. It is found that the pressure drop of tubes partially filled with metal-foam is much higher than that of smooth tubes and the pressure drop increases non-linearly and greatly as the mass flux and vapor quality increase. The flow regime is predicted by monitoring the distribution and fluctuation of cross-section temperatures, from which the stratified wavy flow and annular flow are detected. It is also revealed that the flow condensation heat transfer coefficient for tubes partially filled with annular metal foam is about 2 times that of smooth tube and can be improved as mass flux or vapor quality increases.