Boiling heat transfer characteristics of distributed jet array impingement on metal foam-covered surface

Metal foam has huge potential to enhance jet impingement boiling heat transfer, and the boiling mechanism on metal foam-covered surfaces is uncertain. In this study, the boiling heat transfer characteristics of distributed jet array impingement on metal foam-covered surfaces were experimentally researched, and the effects of operating conditions and metal foam structures were analyzed. The results show that, the critical heat flux and maximum heat transfer coefficient of the metal foam-covered surface with a 20 PPI pore density, 94% porosity, and 3.0 mm thickness are 36.9 % and 22.9 % higher than those of the base surface; as the pore density increases from 20 PPI to 40 PPI, heat transfer performance increases and then decreases; as the porosity decreases from 97 % to 92 %, the critical heat flux and maximum heat transfer coefficient are improved up to 17.4% and 11.9%, respectively; as the thickness increases from 3.0 mm to 4.0 mm, the critical heat flux grows by 7.8 % for 20 PPI, but it decreases by 17.8 % for 40 PPI. The boiling visualization illustrates that, bubble diameter decreases with increasing jet velocity and subcooled degree; bubble departure resistance increases with increasing pore density and thickness or decreasing porosity. New correlations for the heat transfer coefficient and critical heat flux were developed with mean relative errors of 6.4 %-9.1 %.