| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系碩士班 === 94 === This study uses the entropy generation minimization (EGM) method to optimize a saturated vapor flowing slowly onto and condensed on an isothermal horizontal tube. We derive an expression for entropy generation, which accounts for the resultant action of specified irreversibilities of film-wise condensation outside a tube, subjected to different kinds of boundary conditions which include (1) steady isothermal wall temperature, (2) variable (non-isothermal /isothermal) wall temperature.
This thesis combines the EGM technique proposed by Adrian Bejan for a laminar flow with convection heat transfer and the heat transfer approach for laminar film condensation by my adviser, Dr. Yang, to investigate both local and mean dimensionless entropy generation rate of laminar film condensation on a horizontal tube subject with both isothermal wall and variable wall temperature respectively. The present paper uses numerical approach and studies the effects of various working parameters, including Brinkman, Rayleigh, and Jakob numbers on the entropy generation rate. Besides, the irreversibilities ratio of finite temperature difference heat transfer and film flow friction are also studied.
The result shows that local entropy generation rate increases with Brinkman group parameters. As Rayleigh group parameters increase, dimensionless heat transfer coefficient is enhanced, but entropy generation number is augmented too. The result of irreversibility distribution ratio indicates that heat transfer irreversibility dominates over film flow friction irreversibility except around the middle way of streamwise length for the cases .
Finally, the present result is also compared with that different model. Besides, it will offer the electronic enterprise a reference data in the future.
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