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

Tong-Bou Chang

doi:10.1155/2014/172605

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,Sf, 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 differenceψ, and the wall suction parameterSw. 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,NT, increases with an increasing suction parameterSw, whereas the dimensionless entropy generation due to liquid film flow friction,NF, decreases.

Highlights

Film condensation on a horizontal tube has many thermal engineering applications, including chemical vapor deposition, distillation, and heat exchange
This study has examined the entropy generation rate in a laminar condensate film on a horizontal tube with wall suction effects
The dimensionless entropy generation number induced by heat transfer irreversibility is equal to π times the mean Nusselt number, while

Summary

Introduction

Film condensation on a horizontal tube has many thermal engineering applications, including chemical vapor deposition, distillation, and heat exchange. Dung and Yang [13] applied the entropy generation minimization method proposed by Bejan in [8] to optimize film condensation heat transfer on a horizontal tube Their results showed that the optimal group Rayleigh parameter exists over the parametric range investigated for horizontal tube at which the entropy is generated at a minimum rate. Li and Yang [14] applied the entropy generation minimization method to optimize the heat transfer performance of a horizontal elliptical cylinder in a saturated vapor flow. The present study performs an analytical investigation into the effects of the Jakob number, Rayleigh number, Brinkman number, dimensionless temperature difference, and suction force on the dimensionless entropy generation rate for a horizontal tube in a stationary saturated vapor. In performing the analysis, the effects of both the gravitational force and the viscous force are taken into explicit account

Analysis

Results and Discussion

Conclusion