Influence of pore density and porosity on the wet air flow in metal foam under different operation conditions

In order to optimize the parameters of metal foam heat exchanger operating under dehumidifying conditions, the influence of pore density and porosity on the heat transfer and pressure drop characteristics of wet air in metal foam under different conditions were investigated experimentally. The experimental conditions cover PPI (number of pores per inch) of metal foam from 5 to 40 and porosity from 85% to 95%. The results show that, as PPI increases, the global heat transfer coefficient always increases under low relative humidity conditions, while it initially increases then decreases under high relative humidity conditions, presenting a maximum increment of 12-21% at 20 PPI. As the porosity increases from 85% to 95%, the global heat transfer coefficient of wet air in metal foam decreases maximally by 32%, and the pressure drop of wet air in metal foam decreases by 47%.