Effects of temperature-dependent viscosity variation on entropy generation, heat

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Effects of temperature-dependent viscosity variation on entropy generation, heat and fluid flow through a porous-saturated duct of rectangular cross-section

Effect of temperature-dependent viscosity on fully developed forced convection in a duct of rectangular cross-section occupied by a fluid-saturated porous medium is investigated analytically. The Darcy flow model is applied and the viscosity-temperature relation is assumed to be an inverse-linear one. The case of uniform heat flux on the walls,i.e. the H boundary condition in the terminology of Kays and Crawford [12], is treated.For the case of a fluid whose viscosity decreases with temperature, it is found that the effect of the variation is to increase the Nusselt number for heated wails. Having found the velocity and the temperature distribution, the second law of thermodynamics is invoked to find the local and average entropy generation rate. Expressions for the entropy generation rate, the Bejan number, the heat transfer irreversibility, and the fluid flow viscosity variation number, the dimensionless wall heat flux, and the aspect ratio (width to height ratio). These expressions let a parametric study of the problem based on which it is observed that the entropy generated due to flow in a duct of square cross-section is more than those of rectangular counterparts while increasing the aspect ratio decreases the entropy generation rate similar to what previously reported for the clear flow case by Ratts and Raut [14].

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作 者: K. Hooman H. Gurgenci  
作者单位:School of Engineering, the University of Queensland, Brisbane, Australia 
刊 名:应用数学和力学(英文版)  EI SCI
英文刊名:APPLIED MATHEMATICS AND MECHANICS 
年,卷(期):2007 28(1) 
分类号:O3 
关键词:entropy generation rate   forced convection   porous medium   rectangular duct   temperature-dependent viscosity  
机标关键词:entropy generationsecond law of thermodynamicstemperature distributionaspect ratioheat fluxboundary conditionforced convectionNusselt numberporous mediumheat transferfluid flowflow model 
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