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FINITE ELEMENT STUDY OF DDNC IN BOTTOM HEATED ENCLOSURES WITH MASS DIFFUSIVE SIDE WALLS

Nithish Reddy, K. Murugesan
Frontiers in Heat and Mass Transfer (FHMT) 8 - 7 (2017)


Abstract


In this paper DDNC phenomenon in a bottom heated enclosure exposed to mass diffusion from its side walls is investigated numerically. The interplay between thermal and solutal buoyancy forces on fluid circulation and heat transfer rates is studied in three different enclosures of aspect ratios 0.5, 1.0 and 2.0.  Finite element base numerical code has used to solve the governing equations, here velocity and vorticity are taken as primary variables for flow field. Numerical results are well validated with that of the literature. The relative strength of solutal to thermal buoyancy forces is defined by buoyancy ratio parameter ‘N’, numerical investigations were carried out for different values of N in the range of 0 to 10 and three different Rayleigh numbers(Ra=1.0×103,1.0×104,1.0×105). From results it is observed that solutal buoyancy forces broken down the larger fluid cells and promoted local circulations of stronger strength. Increase in contribution of solutal buoyancy force has resulted in a maximum of 12.6%, 14.5% and 51% increase in average Nusselt number for shallow, square and deep enclosures respectively when heat transfer is primarily by convection while the effect of buoyancy ratio is not felt much on heat transfer at diffusion dominant conditions i.e at Ra=1.0×103.


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DOI: http://dx.doi.org/10.5098/hmt.8.7

ISSN: 2151-8629