Filmwise condensation on micro-fin surfaces produced by selective laser melting

Abstract

This paper presents an experimental investigation on the condensation of steam on vertical flat surfaces with arrays of micro-fins. Three micro-fin surfaces (MF1, MF2 and MF3) of the same fin diameter and fin height but with different fin pitch were fabricated by selective laser melting. The surfaces were tested in a condensation chamber where the gravity driven condensate flow and vapor velocity are orthogonal to one another. The effects of fin pitch and vapor velocity on the heat transfer performances of the surfaces were examined. Our results suggest that fin pitch has significant influence on the condensate drainage path as compared to the increase in heat transfer area. In addition, above a certain wall subcooled temperature, the increase in vapor velocity also resulted in the systematic increase in condensation heat flux indicating the significant effects of vapor shear force. In all, up to 1.4 times enhancement in the heat transfer coefficient was achieved with the micro-fin surface with a fin pitch of 300 μm as compared to a plain Al-6061 surface at constant vapor velocity.