Analysis of film condensation heat transfer inside a vertical micro tube with consideration of the meniscus draining effect

In this paper we report on a theoretical analysis of film condensation heat transfer in a vertical micro tube with a thin metal wire welded on its inner surface. Both the radial and the axial distributions of condensate liquid along the tube wall and over the meniscus zone, formed by the wire in contact with the tube inner surface, are determined based on the minimum energy principle over the liquid-vapor two-phase flow system. The influences of the contact angle between the condensate liquid and the channel wall as well as the wire diameter on the condensate distributions and the heat transfer characteristics are examined. It is found that an increase in the wire diameter results in significant enhancement of heat transfer in the channel. It is also demonstrated that the wettability between the wire and the condensate has a little influence on the overall heat transfer coefficients, although it affects the condensate liquid distribution. Compared to a round tube with the same inside diameter, significant enhancement of condensation heat transfer is found for the present configured microchannel.