Influence of surface wettability on liquid drainage characteristics of metal foams under sloshing conditions

Metal foams have great potential for improving the condensation heat transfer characteristics of shell-and-tube heat exchangers in FLNG plants, and the drainage characteristics in metal foam under sloshing conditions should be promoted through modifying the surface wettability. For revealing the liquid drainage mechanism of metal foam with different surface wettability, the influence of surface wettability on liquid drainage characteristics under sloshing conditions was experimentally investigated in the present study. The tested samples include the hydrophilic, uncoated and hydrophobic metal foams; the experimental conditions include foam pore density of 5–40 PPI (pores per inch), the sloshing frequency of 0–1 Hz and the angle from 0° to 25°. The experimental results show that, the decreasing wettability of metal foam promotes the liquid drainage characteristics, and the promotion effect is more significant for the metal foam with larger PPI. The liquid retention mass in metal foam with various surface wettability decreases maximally by 30% under the rolling motions, while it only decreases by 5% under the swaying and heaving motions. The wettability impact factors of the hydrophilic and hydrophobic metal foams under the sloshing conditions are within 0.96–1.33 and 0.26–0.97, respectively. A correlation for predicting the liquid retention mass in metal foam with various wettability under the sloshing conditions is developed within a deviation of 25%.