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ENTROPY GENERATION DUE TO NATURAL CONVECTION WITH NON -UNIFORM HEATING OF POROUS QUADRANTAL ENCLOSURE-A NUMERICAL STUDY

Shantanu Kumar Dutta, Arup Kumar Biswas
Frontiers in Heat and Mass Transfer (FHMT) 10 - 8 (2018)


Abstract


Industrial processes optimization for higher energy efficiency may be effectively carried out based on the thermodynamic approach of entropy generation minimization (EGM). This approach provides the key insights on how the available energy (exergy) is being destroyed during the process and the ways to minimize its destruction. In this study, EGM approach is implemented for the analysis of optimal thermal mixing and temperature uniformity due to natural convection in quadrantal cavity filled with porous medium for the material processing applications. Effect of the permeability of the porous medium and the role of non-uniform heating in enhancing the thermal mixing, temperature effects and minimization of entropy generation is analyzed. The numerical solutions are obtained using  finite element method. Stream lines , Isotherms and entropy generation  results are depicted for Ra=106, 1.7x105, 104 and  for Da=10-3, 10-4 and 10-5 at Pr=0.71.It is found that at lower Darcy number (Da), the thermal mixing is low and the heat transfer irreversibility dominates the total entropy generation. In contrast, thermal mixing is improved due to enhanced convection at higher Da. Also observed is that fluid friction irreversibility  dominates over heat transfer irreversibility for  only Da=10-3 Ra=106. The local entropy generation is maximum at the bottom wall, while at the center and top of the enclosure it becomes minimum. Based on EGM analysis, it is established that larger thermal mixing at high Darcy number may  be  recommended as the total entropy production is  not significant at high Darcy numbers.


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DOI: http://dx.doi.org/10.5098/hmt.10.8

ISSN: 2151-8629