Thermodynamic Second Law Analysis of Forced-Convection Film Condensation on a Horizontal tube with Uniform Wall Heat Flux

• Main Authors: Yung-Sian Chen, 陳永祥
• Other Authors: Sheng-An Yang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/37403286094205603168

碩士 === 國立高雄應用科技大學 === 模具工程系 === 97 === This paper aims to perform the thermodynamic second law analysis of forced-convection film condensation on a horizontal tube with uniform wall heat flux. We adopted Shekriladze and Gomelauri approach to deal with the interfacial vapor shear stress, and Nusselt film condensation model to investigate laminar film condensation heat transfer. Further, owing to the effect of pressure gradient, the separation angles of the condensate film layer ,θc are obtained for various dimensionless pressure gradient parameters, P* and their corresponding dimensionless Grashof’s parameters, Gr* via the fourth-order Runge-Kutta numerical method. Next, based on Bejan’s entropy generation minimization technique, both the local and mean entropy generation rate are also determined to understand which irreversibility factor, like film flow friction, or finite-temperature difference heat transfer dominates the entropy generation rate in terms of pressure gradient parameter, Grashof’s parameter, Brinkman number, and Reynold number. Note the forced-convection film dominated condensation when modified Grashof’s parameter is smaller than 1, the case without taking account of pressure gradient i.e, P*=0 applies to uniform surface heat flux condition. Finally, the entropy rate and irreversibility factor increases as the Brinkman number increases. Besides, the dimensionless entropy generation numbers are found to increase with Reynold number and the dimensionless heat transfer coefficient too. The analysis of entropy generation for the case of uniform wall heat flux can also be a good future reference for designing heat pipe.