EXPERIMENTAL INVESTIGATION ON FLOW CONDENSATION HEAT TRANSFER IN HYDROPHOBIC ANNULAR METAL-FOAM TUBE

The vapor flow condensation heat transfer in tube filled with hydrophobic annular metal foam is experimentally investigated. The surface of annular metal foam is hydrophobically modified through chemical corrosion and molecular self-assembly technology. The thickness of the metal foam is 2mm and cell size is 10PPI. The thermocouples are welded in groove to measure wall temperature. The effects of vapor mass flow, cooling water temperature and vapor quality are analyzed. The results show that the pressure drop and average heat transfer coefficient of tubes filled with annular metal foam increase with increasing vapor mass flow or vapor quality. According to wall temperature distribution, it is predicted that flow pattern is annular flow at vapor entrance and the stratified flow is located at the distance from 0.5m to 0.9m. The average heat transfer coefficient of hydrophobic annular metal foam tube increases approximately 1.2 times compared to untreated metal foam tube.