Combined Heat and Mass Transfer by Natural Convection in a Vertical Enclosure

1987 ◽  
Vol 109 (1) ◽  
pp. 104-112 ◽  
Author(s):  
O. V. Trevisan ◽  
A. Bejan
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Lewis Number ◽  
Convective Mass Transfer ◽  
Transfer Rates ◽  
Rectangular Slot ◽  
Transfer Path ◽  
Mass Fluxes ◽  
Buoyancy Ratio

The phenomenon of natural convection caused by combined temperature and concentration buoyancy effects is studied analytically and numerically in a rectangular slot with uniform heat and mass fluxes along the vertical sides. The analytical part is devoted to the boundary layer regime where the heat and mass transfer rates are ruled by convection. An Oseen-linearized solution is reported for tall spaces filled with mixtures characterized by Le = 1 and arbitrary buoyancy ratios. The effect of varying the Lewis number is documented by a similarity solution valid for Le >1 in heat-transfer-driven flows, and for Le <1 in mass-transfer-driven flows. The analytical results are validated by numerical experiments conducted in the range 1≤H/L≤4, 3.5×105≤Ra≤7×106, −11≤n≤9, 1≤Le≤40, and Pr=0.7, 7. “Massline” patterns are used to visualize the convective mass transfer path and the flow reversal observed when the buoyancy ratio n passes through the value −1.

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).

Radiation Effect on Heat and Mass Transfer by Natural Convection from a Horizontal Surface Embedded in a Porous Medium

2018 ◽  
Vol 16 ◽  
pp. 140-157 ◽  
Author(s):  
Nasreen Bano ◽  
Oluwole Daniel Makinde ◽  
B.B. Singh ◽  
Shoeb R. Sayyed
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Saturated Porous Medium ◽  
Lewis Number ◽  
Similarity Solutions ◽  
Horizontal Surface ◽  
Integral Approach ◽  
Power Law Exponent

This paper deals with the study of the heat and mass transfer characteristics of natural convection from a horizontalsurface embedded in a radiating fluid saturated porous medium. Similarity solutions for buoyancy induced heat and masstransfer from a horizontal surface, where the wall temperature and concentration are a power function of distance fromthe origin, are obtained by using an integral approach of Von Karman type. The effects of the governing parameters suchas buoyancy ratio, Lewis number, radiation parameter and the power-law exponent on local Nusselt and local Sherwoodnumbers have been investigated both numerically and graphically.

Coupled Heat and Mass Transfer by Mixed Convection From a Buried Pipe With Leakage

2003 ◽  
Author(s):  
C. C. Ngo ◽  
F. C. Lai
Keyword(s):  
Mass Transfer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Heat And Mass Transfer ◽  
Sherwood Number ◽  
Numerical Solutions ◽  
Lewis Number ◽  
The Body ◽  
Buried Pipe ◽  
Buoyancy Ratio

Numerical solutions are presented for combined heat and mass transfer by mixed convection induced from a buried pipe with leakage. Two locations of leakage are considered in the present study: one is on top of the pipe and the other is at the bottom of the pipe. The governing equations formulated in the body-fitted coordinates are solved via the finite difference method. A parametric study has been performed to investigate the effects of Rayleigh number, Peclet number, Lewis number, and buoyancy ratio N on the heat and mass transfer results. It is found that both the Nusselt number and Sherwood number increase for the aiding flows (N > 0) and decrease for the opposing flows (N < 0). For aiding flows, Sherwood number increases with the Lewis number but Nusselt number decreases with the Lewis number.

Effect of Double Stratification on Free Convection in a Micropolar Fluid

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
D. Srinivasacharya ◽  
Ch. RamReddy
Keyword(s):  
Mass Transfer ◽  
Free Convection ◽  
Heat And Mass Transfer ◽  
Micropolar Fluid ◽  
Double Stratification ◽  
Transfer Rates ◽  
Keller Box Method ◽  
Mass Fluxes ◽  
Special Cases ◽  
Good Agreement

This paper analyzes the flow and heat and mass transfer characteristics of the free convection on a vertical plate with uniform and constant heat and mass fluxes in a doubly stratified micropolar fluid. The nonlinear governing equations and their associated boundary conditions are initially cast into dimensionless forms by pseudosimilarity variables. The resulting system of equations is then solved numerically using the Keller-box method. The numerical results are compared and found to be in good agreement with previously published results on special cases of the problem. The obtained results are displayed graphically to illustrate the effect of the micropolar and stratification parameters on the dimensionless velocity, microrotation, wall temperature, and wall concentration. The numerical values of the skin friction, wall couple stress, and heat and mass transfer rates for different values of governing parameters are also tabulated.

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.

Thermo-Solutal Natural Convection in an Anisotropic Porous Enclosure Due to Non-Uniform Temperature and Concentration at Bottom Wall

2015 ◽  
Vol 7 (5) ◽  
pp. 644-662 ◽  
Author(s):  
Ashok Kumar ◽  
Pravez Alam ◽  
Prachi Fartyal
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Orientation Angle ◽  
Darcy Number ◽  
Bottom Wall ◽  
Transfer Rates ◽  
The Impact

AbstractThis article summaries a numerical study of thermo-solutal natural convection in a square cavity filled with anisotropic porous medium. The side walls of the cavity are maintained at constant temperatures and concentrations, whereas bottom wall is a function of non-uniform (sinusoidal) temperature and concentration. The non-Darcy Brinkmann model is considered. The governing equations are solved numerically by spectral element method using the vorticity-stream-function approach. The controlling parameters for present study are Darcy number (Da), heat source intensity i.e., thermal Rayleigh number (Ra), permeability ratio (K*), orientation angle (ϕ). The main attention is given to understand the impact of anisotropy parameters on average rates of heat transfer (bottom,Nub, sideNus) and mass transfer (bottom,Shb, side,Shs) as well as on streamlines, isotherms and iso-concentration. Numerical results show that, for irrespective value ofK*, the heat and mass transfer rates are negligible for 10−7≤Da≤ 10−5,Ra= 2 × 105andϕ= 45°. However a significant impact appears on Nusselt and Sherwood numbers whenDalies between 10−5to 10−4. The maximum bottom heat and mass transfer rates (Nub, Sub) is attained atϕ= 45°, whenK*=0.5 and 2.0. Furthermore, both heat and mass transfer rates increase on increasing Rayleigh number (Ra) for all the values ofK*. Overall, It is concluded from the above study that due to anisotropic permeability the flow dynamics becomes complex.

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