Heat transfer and pressure drop characteristics of wet air flow in metal foams with different structures and surface wettability during dehumidifying conditions

摘要

To optimize the metal foam heat exchangers under dehumidifying conditions, the heat transfercoefficient (HTC) and pressure drop of wet air in metal foams with different structure and surfacewettability were obtained experimentally. The pore density of tested metal foams is 5-40 PPI, andthe porosity is 0.85-0.95. The wettability includes the hydrophobic, hydrophilic and uncoated surface,with proceeding contact angles from 15.4° to 161.2°. The results show that, the HTC of wet air inmetal foams are enhanced by 4%-33% and 2-21% by hydrophobic and hydrophilic coating,respectively; the pressure drops are obviously increased by hydrophobic coating and maximumlydecreased by 20% by hydrophilic coating; as PPI increases, the pressure drop in metal foams areincreased, while the HTC is firstly increased then decreased at most dehumidifying conditions; asporosity increases, the HTC and pressure drop are both decreased. Considering the comprehensiveperformance, 20PPI is the best metal foam pore density with best comprehensive performance, while0.85 and 0.95 are the best porosity for hydrophobic and uncoated metal foams, respectively.