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Mathematical Problems in Engineering
Volume 2014, Article ID 172605, 8 pages
http://dx.doi.org/10.1155/2014/172605
Research Article

Theoretical Analysis of Effects of Wall Suction on Entropy Generation Rate in Laminar Condensate Layer on Horizontal Tube

1Department of Mechanical and Energy Engineering, National Chiayi University, No. 300, Syuefu Road, Chiayi City 600, Taiwan
2Center of Energy Research & Sensor Technology, National Chiayi University, No. 300, Syuefu Road, Chiayi City 600, Taiwan

Received 28 August 2014; Revised 11 November 2014; Accepted 17 November 2014; Published 4 December 2014

Academic Editor: Hang Xu

Copyright © 2014 Tong-Bou Chang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The effects of wall suction on the entropy generation rate in a two-dimensional steady film condensation flow on a horizontal tube are investigated theoretically. In analyzing the liquid flow, the effects of both the gravitational force and the viscous force are taken into account. In addition, a film thickness reduction ratio, , is introduced to evaluate the effect of wall suction on the thickness of the condensate layer. The analytical results show that, the entropy generation rate depends on the Jakob number Ja, the Rayleigh number Ra, the Brinkman number Br, the dimensionless temperature difference , and the wall suction parameter . In addition, it is shown that in the absence of wall suction, a closed-form correlation for the Nusselt number can be derived. Finally, it is shown that the dimensionless entropy generation due to heat transfer, , increases with an increasing suction parameter , whereas the dimensionless entropy generation due to liquid film flow friction, , decreases.