Combined Heat and Mass Transfer by Natural Convection With Opposing Buoyancies

1993 ◽  
Vol 115 (3) ◽  
pp. 606-612 ◽  
Author(s):  
R. L. Mahajan ◽  
D. Angirasa
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Numerical Solutions ◽  
Boundary Layer Analysis ◽  
Layer Analysis ◽  
Wide Range ◽  
Schmidt Numbers ◽  
Buoyancy Ratio

A numerical study is presented for combined heat and mass transfer by natural convection from a vertical surface with opposing buoyancy effects. A comparison with similarity solutions shows that boundary layer analysis is suitable only when the two buoyant forces aid each other. For opposing flows the boundary layer analysis does not predict the transport rates accurately. A detailed comparison with experimental data with opposing buoyancies shows good agreement between the data and the numerical solutions. The heat and mass transfer rates follow complex trends depending on the buoyancy ratio and the Prandtl and Schmidt numbers. Comprehensive Nusselt and Sherwood number data are presented for a wide range of thermal Grashof number, buoyancy ratio, and Prandtl and Schmidt numbers.

Numerical simulation of unsteady double-diffusive natural convection within an inclined parallelepipedic enclosure

2014 ◽  
Vol 25 (11) ◽  
pp. 1450058 ◽  
Author(s):  
Fakher Oueslati ◽  
Brahim Ben-Beya ◽  
Taieb Lili
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Three Dimensional ◽  
Transfer Rates ◽  
Flow Energy ◽  
Wide Range ◽  
Inclination Angles ◽  
Volume Method ◽  
Buoyancy Ratio ◽  
Double Diffusive

Unsteady three-dimensional (3D) double diffusive convection in tilted enclosure having a parallelepipedic shape has been analyzed numerically. The governing unsteady, 3D flow, energy and concentration transport equations, have been solved using an accelerated multigrid implicit volume method. Main attention was paid to the effects of the Rayleigh number Ra , buoyancy ratio N and the inclination angle γ of the cavity on the flow structure and heat and mass transfer rates. Typical distributions of velocity contours, temperature and concentration fields in wide range of defining parameters 103 ≤ Ra ≤ 2 × 104, -5 ≤ N ≤ 5 have been obtained. It is found, that the optimal heat and mass transfer rates for the aiding situation have been observed at two particular inclination angles namely 30° and 75° about the horizontal direction. It should be noted that the flow undergoes a periodic behavior for particular parameters Ra = 104 and γ = 75° according to the aiding flow case. The results also suggest that when N is in range -2 ≤ N ≤ -0.6, the flow continues to be three-dimensional keeping different heat and mass rates. Furthermore, it has been argued that the 2D assumption can be adopted for the 3D flows when the buoyancy ratio N is in range (-0.5–0).

Heat and Mass Transfer Associated With Condensation on a Moving Drop: Solutions for Intermediate Reynolds Numbers by a Boundary Layer Formulation

1985 ◽  
Vol 107 (2) ◽  
pp. 409-416 ◽  
Author(s):  
T. Sundararajan ◽  
P. S. Ayyaswamy
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Saturated Vapor ◽  
Time History ◽  
Local Heat ◽  
Surface Shear Stress ◽  
Contact Heat ◽  
Surface Shear ◽  
Wide Range

Condensation heat and mass transfer to a liquid drop moving in a mixture of saturated vapor and a noncondensable have been evaluated. The Reynolds number of the drop motion is 0(100). The quasi-steady, coupled, boundary layer equations for the flow field and the transport in the gaseous phase are simultaneously solved. The heat transport inside the drop is treated as a transient process. Results are presented for the heat and mass transport rates to the drop, the surface shear stress, the velocity profiles across the boundary layer, and the temperature-time history of the drop. The comparisons of results with experimental data, where available, show excellent agreement. Tables summarizing results appropriate to a wide range of condensation rates have been included. Local heat and mass transfer rates have also been presented. These features will make the paper useful to the designer of direct contact heat transfer equipment.

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