Combined Heat and Mass Transfer in Mixed Convection over a Horizontal Flat Plate

1980 ◽  
Vol 102 (3) ◽  
pp. 538-543 ◽  
Author(s):  
T. S. Chen ◽  
F. A. Strobel
Keyword(s):  
Mass Transfer ◽  
Flat Plate ◽  
Heat And Mass Transfer ◽  
Transfer Rate ◽  
Buoyancy Force ◽  
Schmidt Number ◽  
Thermal Buoyancy ◽  
Buoyancy Forces ◽  
Thermal Buoyancy Force ◽  
Species Diffusion

The combined effects of buoyancy forces from thermal and species diffusion on the heat and mass transfer characteristics are analyzed for laminar boundary layer flow over a horizontal flat plate. The analysis is restricted to processes with low concentration levels such that the interfacial velocities due to mass diffusion and the diffusion-thermo/thermo-diffusion effects can be neglected. Numerical results for friction factor, Nusselt number, and Sherwood number are presented for gases having a Prandtl number of 0.7, with Schmidt numbers ranging from 0.6 to 2.0. In general, it is found that, for the thermally assisting flow, the surface heat and mass transfer rates as well as the wall shear stress increase with increasing thermal buoyancy force. These quantities are further enhanced when the buoyancy force from species diffusion assists the thermal buoyancy force, but are reduced when the two buoyancy forces oppose each other. While a higher heat transfer rate is found to be associated with a lower Schmidt number, a higher mass transfer rate occurs at a higher Schmidt number.

Numerical Analysis of Interaction Between Inertial and Thermosolutal Buoyancy Forces on Convective Heat Transfer in a Lid-Driven Cavity

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
D. Senthil kumar ◽  
K. Murugesan ◽  
Akhilesh Gupta
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Buoyancy Force ◽  
Inertial Force ◽  
Driven Cavity ◽  
Thermal Buoyancy ◽  
Buoyancy Forces ◽  
Thermal Buoyancy Force

In this paper, results on double diffusive mixed convection in a lid-driven cavity are discussed in detail with a focus on the effect of interaction between fluid inertial force and thermosolutal buoyancy forces on convective heat and mass transfer. The governing equations for the mathematical model of the problem consist of vorticity transport equation, velocity Poisson equations, energy equation and solutal concentration equation. Numerical solution for the field variables are obtained by solving the governing equations using Galerkin’s weighted residual finite element method. The interaction effects on convective heat and mass transfer are analyzed by simultaneously varying the characteristic parameters, 0.1<Ri<5, 100<Re<1000, and buoyancy ratio (N), −10<N<10. In the presence of strong thermosolutal buoyancy forces, the increase in fluid inertial force does not make significant change in convective heat and mass transfer when the thermal buoyancy force is smaller than the fluid inertial force. The fluid inertial force enhances the heat and mass transfer only when the thermal buoyancy force is either of the same magnitude or greater than that of the fluid inertial force. The presence of aiding solutal buoyancy force enhances convective heat transfer only when Ri becomes greater than unity but at higher buoyancy ratios, the rate of increase in heat transfer decreases for Re=400 and increases for Re=800. No significant change in heat transfer is observed due to aiding solutal buoyancy force for Ri≤1 irrespective of the Reynolds number.

Effects of Mass Transfer and Free-Convection Currents on the Flow Near a Moving Vertical Plate With Ramped Wall Temperature

2009 ◽  
Author(s):  
M. Narahari ◽  
Binay K. Dutta
Keyword(s):  
Mass Transfer ◽  
Free Convection ◽  
Skin Friction ◽  
Heat And Mass Transfer ◽  
Buoyancy Force ◽  
Vertical Plate ◽  
Flow Temperature ◽  
Thermal Buoyancy ◽  
Laplace Transform Technique ◽  
Thermal Buoyancy Force

A theoretical analysis to the problem of free convection flow induced by an infinite moving vertical plate subject to a ramped surface temperature with simultaneous mass transfer to or from the surface is presented. The plate temperature increases linearly over a specified period of time until it reaches a constant value. Diffusional mass transfer occurs at the surface contributing to the density gradient in the boundary layer. An exact analytical solution to the governing equations for flow, temperature and concentration with coupled boundary conditions in the dimensionless form have been developed using the Laplace transform technique. Heat and mass transfer at the plate are assumed to be purely diffusive in nature. The cases of impulsive start and uniformly accelerating start of the plate are considered and solutions for the flow, temperature and concentration fields are derived. The effects of different system parameters have been studied in terms of relevant dimensionless groups such as Grashof number (Gr), Prandtl number (Pr), Schmidt number (Sc), time (t) and the mass to thermal buoyancy ratio (N). The possible cases of the last parameter, namely N = 0 (the buoyancy force is due to thermal diffusion only), N &gt; 0 (the mass buoyancy force acts in the same direction of thermal buoyancy force) and N &lt; 0 (the mass buoyancy force acts in the opposite direction of thermal buoyancy force) are investigated and their effects on the velocity field and skin-friction are explicitly determined. The ramped temperature boundary condition predictably has an enhancing effect on the skin friction. The mass flux to the plate influences the velocity and hence the skin friction. A critical analysis of the coupled heat and mass transfer phenomena is provided. The free convection near a ramped temperature plate has also been compared with the flow near a plate with constant temperature as a limiting case.

Distribution of Mass Transfer Rate and Wall Shear Stress Behind Simple Rectangular Stenosis in Pulsating Flow

1989 ◽  
Vol 111 (1) ◽  
pp. 47-54 ◽  
Author(s):  
R. Yamaguchi
Keyword(s):  
Mass Transfer ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Transfer Rate ◽  
Schmidt Number ◽  
Fluid Dynamic ◽  
Mass Transfer Rate ◽  
Pulsating Flow ◽  
Flow Through ◽  
Wall Shear

The distributions of mass transfer rate and wall shear stress in sinusoidal laminar pulsating flow through a two-dimensional asymmetric stenosed channel have been studied experimentally and numerically. The distributions are measured by the electrochemical method. The measurement is conducted at a Reynolds number of about 150, a Schmidt number of about 1000, a nondimensional pulsating frequency of 3.40, and a nondimensional flow amplitude of 0.3. It is suggested that the deterioration of an arterial wall distal to stenosis may be greatly enhanced by fluid dynamic effects.

A T-RANS/VLES Approach to Indoor Climate Simulations

2002 ◽  
Author(s):  
S. Kenjeresˇ ◽  
K. Hanjalic´ ◽  
S. B. Gunarjo
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Large Scale ◽  
Single Point ◽  
Ventilation System ◽  
Convective Motion ◽  
Wall Friction ◽  
Indoor Climate ◽  
Thermal Buoyancy ◽  
Order Of Magnitude

For accurate prediction of flow, scalar transport and wall heat and mass transfer in complex building space we propose a time-dependent RANS (T-RANS) approach which resolves in time and space the large-scale convective motion and associated deterministic eddy structure. The residual (“subscale”) turbulence is modeled by a single-point closure. The method can be regarded as Very Large Eddy Simulations (VLES) since the deterministic and modeled contribution to the turbulence moments are of the same order of magnitude. The modeled part becomes dominant in the near-wall regions where there are no large eddies and the proper choice of the subscale model is especially important for predicting wall friction and heat transfer. We use an ensemble-averaged 〈k〉 - 〈ε〉 - 〈θ2〉 algebraic stress/flux/concentration closure as the subscale model which can provide information about the stress and heat/species flux anisotropies. The method is especially advantageous for predicting flows driven or affected by thermal buoyancy, for which the conventional eddy-viscosity/diffusivity RANS models and gradient transport hypotheses are known to fail even in simple generic configurations. The approach was validated in a series of buoyancy-driven flows for which experimental, DNS and LES data are available. Examples of full-scale application include computational simulations of real occupied and furnished residential or office space in which the furniture elements and persons are treated as passive blocking elements. The simulation showed that the T-RANS approach can be used as a reliable tool for a variety of applications such as optimization of heating and ventilation system, building space insulation, indoor quality, safety measures related to smoke and fire spreading, as well as for accurate wall heat and mass transfer predictions.

Heat and mass transfer from a flat plate of finite thickness to a boundary layer flow with transpiration

1997 ◽  
Vol 38 (10-13) ◽  
pp. 1209-1218 ◽  
Author(s):  
Shigeru Mori ◽  
Mikio Kumita ◽  
Tohru Takahashi ◽  
Akira Tanimoto ◽  
Mikio Sakakibara
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Flat Plate ◽  
Heat And Mass Transfer ◽  
Boundary Layer Flow ◽  
Finite Thickness ◽  
Layer Flow
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