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Article
Publication date: 15 May 2009

M.A. EL‐Hakiem

The purpose of this paper is to highlight the effect of combined heat and mass transfer characteristics of magnetohydrodynamic (MHD) free convection flow of an…

Abstract

Purpose

The purpose of this paper is to highlight the effect of combined heat and mass transfer characteristics of magnetohydrodynamic (MHD) free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux, taking into consideration the effects of uniform transverse magnetic field and thermal radiation.

Design/methodology/approach

An analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow past a circular cylinder surface under the effect of thermal radiation with uniform heat and mass flux. By using Lie group method, the infinitesimal generators of governing equations are calculated. Using the resulting generators for the boundary value problem, the equations are transformed into an ordinary differential system. Numerical solutions of the outcoming non‐linear differential equations are found by using a combination of a Runge–Kutta algorithm and shooting technique.

Findings

Application of a magnetic field normal to the flow of an electrically conducting fluid gives rise to a resistive force that acts in the direction opposite to that of the flow. This resistive force tends to slow down the motion of the fluid along the cylinder and causes increases in its temperature and concentration and hence the respective changes in the wall shear stress, local Nusselt and Sherwood numbers as the magnetic parameter, respectively are changed with various values of angle which is measured in degrees from the front stagnation point on the surface. It is noted that these coefficients reduced as the magnetic parameter increases. Also, the effect of thermal radiation works as a heat source and so the quantity of heat added to the fluid increases, therefore the local Nusselt number reduced as the radiation parameter increases.

Research limitations/implications

An analysis is performed to study the momentum, combined heat and mass transfer characteristics of MHD free convection flow of an electrically conducting Newtonian fluid on circular cylinder with uniform heat/mass flux with the effects of uniform transverse magnetic field and thermal radiation.

Practical implications

This paper provides a very useful source of coefficient of heat and mass transfer values for engineers planning to transfer heat and mass by using electrically conducting gases with uniform heat/mass flux.

Originality/value

The combined heat and mass transfer of an electrically conducting gases on free convection flow in the presence of magneto and thermal radiation effects are investigated and can be used by different engineers working on industry, geothermal, geophysical, technological and engineering applications.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 19 no. 3/4
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 26 August 2014

Ali J. Chamkha, M. Rashad and Rama Subba Reddy Gorla

The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type…

Abstract

Purpose

The purpose of this paper is to present a boundary layer analysis for the mixed convection past a vertical wedge in a porous medium saturated with a power law type non-Newtonian nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, Lewis number Le and the power law exponent n. The dependency of the friction factor, surface heat transfer rate (Nusselt number) and mass transfer rate on these parameters has been discussed.

Design/methodology/approach

This general non-linear problem cannot be solved in closed form and, therefore, a numerical solution is necessary to describe the physics of the problem. An implicit, tri-diagonal finite-difference method has proven to be adequate and sufficiently accurate for the solution of this kind of problems. Therefore, it is adopted in the present study. Variable step sizes were used. The convergence criterion employed in this study is based on the difference between the current and the previous iterations. When this difference reached 10−5 for all the points in the η directions, the solution was assumed to be converged, and the iteration process was terminated.

Findings

The results indicate that as the buoyancy ratio parameter (Nr) and thermophoresis parameter (Nt) increase, the friction factor increases whereas the heat transfer rate (Nusselt number) and mass transfer rate (Sherwood number) decrease. As the Brownian motion parameter (Nb) increases, the friction factor and surface mass transfer rates increase whereas the surface heat transfer rate decreases. As Le increases, mass transfer rates increase. As the power law exponent n increases, the heat and mass transfer rates increase.

Research limitations/implications

The analysis is valid for natural convection dominated regime. The combined forced and natural convection dominated regimes will be reported in a future work.

Practical implications

The approach used is useful in optimizing the porous media heat transfer problems in geothermal energy recovery, crude oil extraction, ground water pollution, thermal energy storage and flow through filtering media.

Originality/value

The results of the study may be of some interest to the researchers of the field of porous media heat transfer. Porous foam and microchannel heat sinks used for electronic cooling are optimized utilizing the porous medium. The utilization of nanofluids for cooling of microchannel heat sinks requires understanding of fundamentals of nanofluid convection in porous media.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 30 May 2008

Shuhong Liu, Shengcai Li, Liang Zhang and Yulin Wu

The purpose of this paper is to provide a mixture model with modified mass transfer expression for calculating cavitating (two‐phase) flow.

Abstract

Purpose

The purpose of this paper is to provide a mixture model with modified mass transfer expression for calculating cavitating (two‐phase) flow.

Design/methodology/approach

The mass transfer relations are derived based on the mechanics of evaporation and condensation, in which the mass and momentum transfer count for factors such as non‐dissolved gas, turbulence, surface tension, phase‐change rate, etc.

Findings

As shown by two calculation examples, the modified model can predict the cavitating flow with high accuracy, agreeing well with experimental results.

Originality/value

The methods described are of value in improving stability in numerical calculations.

Details

Engineering Computations, vol. 25 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 28 October 2013

R.S.R. Gorla and Anwar Hossain

The purpose of this work is to study the mixed convection boundary layer flow past a vertical cylinder in a porous medium saturated with a nanofluid. Numerical results for…

Abstract

Purpose

The purpose of this work is to study the mixed convection boundary layer flow past a vertical cylinder in a porous medium saturated with a nanofluid. Numerical results for friction factor, surface heat transfer rate and mass transfer rate have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt and Lewis number Le. The dependency of the surface heat transfer rate (Nusselt number) and mass transfer rate on these parameters has been discussed.

Design/methodology/approach

Solutions of the set of non-similarity equations are obtained by employing the implicit finite difference method together with Keller box elimination method.

Findings

It was found that the heat transfer rate decreases and mass transfer rates increase as Lewis number increases. The heat and mass transfer rates increase as the buoyancy ration parameter increases. As the thermophoresis parameter Nt increases, the heat transfer rate decreases where as the mass transfer rate increases. As the Brownian parameter Nb increases, the heat transfer rate decreases. Brownian motion decelerates the flow in the nanofluid boundary layer. Brownian diffusion promotes heat conduction. The heat and mass transfer rates increase as the buoyancy ratio number Nr increases. The Brownian motion and thermophoresis of nanoparticles increases the effective thermal conductivity of the nanofluid. Both Brownian diffusion and thermophoresis give rise to cross diffusion terms that are similar to the familiar Soret and Dufour cross-diffusion terms that arise with a binary fluid.

Research limitations/implications

The analysis is valid for steady, mixed convection two-dimensional boundary layer flow in a nanofluid-saturated Darcy porous medium. An extension to non-Darcy porous medium is left as a part of future study.

Practical implications

The research is applicable for enhancing heat exchanger effectiveness by employing nanofluids.

Originality/value

The study is useful to engineers interested in designing heat exchangers, water and atmospheric pollution.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 23 no. 8
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 11 February 2021

Yun Su, Miao Tian, Yunyi Wang, Xianghui Zhang and Jun Li

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal…

Abstract

Purpose

The purpose of this paper is to study heat and steam transfer in a vertical air gap and improve thermal protective performance of protective clothing under thermal radiation and hot steam.

Design/methodology/approach

An experiment-based model was introduced to analyze heat and moisture transfer in the vertical air gap between the protective clothing and human body. A developed test apparatus was used to simulate different air gap sizes (3, 6, 9, 12, 15, 18, 21 and 24 mm). The protective clothing with different air gap sizes was subjected to dry and wet heat exposures.

Findings

The increase of the air gap size reduced the heat and moisture transfer from the protective clothing to the skin surface under both heat exposures. The minimum air gap size for the initiation of natural convection in the dry heat exposure was between 6 and 9 mm, while the air gap size for the occurrence of natural convection was increased in the wet heat exposure. In addition, the steam mass flux presented a sharp decrease with the rising of the air gap size, followed by a stable state, mainly depending on the molecular diffusion and the convection mass transfer.

Originality/value

This research provides a better understanding of the optimum air gap under the protective clothing, which contributes to the design of optimum air gap size that provided higher thermal protection against dry and wet heat exposures.

Details

International Journal of Clothing Science and Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0955-6222

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Article
Publication date: 27 May 2014

P.K. Kameswaran, Z.G. Makukula, P. Sibanda, S.S. Motsa and P.V.S.N. Murthy

The purpose of this paper is to study heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet placed in saturated porous medium with…

Abstract

Purpose

The purpose of this paper is to study heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet placed in saturated porous medium with internal heat generation or absorption. The authors further introduce a new algorithm for solving heat transfer problems in fluid mechanics. The model used for the nanofluid incorporates the nanoparticle volume fraction parameter and a consideration of the chemical reaction effects among other features.

Design/methodology/approach

The partial differential equations for heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet were transformed into a system of nonlinear ordinary differential equations. Exact solutions for the boundary layer equations were obtained in terms of a confluent hypergeometric series. A novel spectral relaxation method (SRM) is used to obtain numerical approximations of the governing differential equations. The exact solutions are used to test the convergence and accuracy of the SRM.

Findings

Results were obtained for the fluid properties as well as the skin friction, and the heat and mass transfer rates. The results are compared with limiting cases from previous studies and they show that the proposed technique is an efficient numerical algorithm with assured convergence that serves as an alternative to numerical methods for solving nonlinear boundary value problems.

Originality/value

A new algorithm is used for the first time in this paper. In addition, new exact solutions for the energy and mass transport equations have been obtained in terms of a confluent hypergeometric series.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 5
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 13 April 2012

Ali J. Chamkha, A.M. Rashad and Humood F. Al‐Mudhaf

The purpose of this paper is to solve the problem of steady, laminar, coupled heat and mass transfer by MHD natural convective boundary‐layer flow over a permeable…

Abstract

Purpose

The purpose of this paper is to solve the problem of steady, laminar, coupled heat and mass transfer by MHD natural convective boundary‐layer flow over a permeable truncated cone with variable surface temperature and concentration in the presence of thermal radiation and chemical reaction effects.

Design/methodology/approach

The governing equations are derived and transformed into a set of non‐similar equations which are then solved by an adequate implicit finite difference method.

Findings

It is found that the presence of thermal radiation, magnetic field and chemical reaction have significant effects on the rates of heat and mass transfer. The variation of the wall temperature and concentration exponent contribute to significant changes in the Nusselt and Sherwood numbers as well.

Originality/value

The titled problem with the various considered effects has not been solved before and it is of special importance in various industries. The problem is original.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 22 no. 3
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 7 October 2014

A.M. Abd-Alla, S.M. Abo-Dahab, A. Kilicman and R.D. El-Semiry

The purpose of this paper is to investigate the peristaltic flow of an incompressible Newtonian fluid in a channel with compliant walls. The effects of rotation and heat…

Abstract

Purpose

The purpose of this paper is to investigate the peristaltic flow of an incompressible Newtonian fluid in a channel with compliant walls. The effects of rotation and heat and mass transfer are also taken into account. The governing equations of two dimensional fluid have been simplified under long wavelength and low Reynolds number approximation. An exact solutions is presented for the stream function, temperature, concentration field, velocity and heat transfer coefficient.

Design/methodology/approach

The effect of the concentration distribution, heat and mass transfer and rotation on the wave frame are analyzed theoretically and computed numerically. Numerical results are given and illustrated graphically in each case considered. Comparison was made with the results obtained in the presence and absence of rotation and heat and mass transfer.

Findings

The results indicate that the effect of the permeability and rotation are very pronounced in the phenomena.

Originality/value

The objective of the present analysis is to analyze the effects of rotation, heat and mass transfer and compliant walls on the peristaltic flow of a viscous fluid.

Details

Multidiscipline Modeling in Materials and Structures, vol. 10 no. 3
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 1 November 1997

K.S. Sujatha, A. Mani and S. Srinivasa Murthy

Develops a fine element method employing Galerkin’s approach for the analysis of a vertical tubular bubble absorber working with R22‐DMF as working fluid. Aims to provide…

Abstract

Develops a fine element method employing Galerkin’s approach for the analysis of a vertical tubular bubble absorber working with R22‐DMF as working fluid. Aims to provide an understanding of the absorption process which helps in the design of bubble absorbers. Numerical experiments have also been carried out with ammonia‐water combination for the sake of comparison with the results in the literature and the agreement is found to be good. Suggests a correlation for mass transfer coefficient for vertical tubular bubble absorbers working with R22‐DMF. The use of the correlation can either be in estimating the mass transfer rates, or in fixing up the major design parameters such as diameter and length required for complete absorption.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 7 no. 7
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 5 June 2017

M.M. Rahman, Sourav Saha, Satyajit Mojumder, Khan Md. Rabbi, Hasnah Hasan and Talaat A. Ibrahim

The purpose of this investigation is to determine the nature of the flow field, temperature distribution and heat and mass transfer in a triangular solar collector…

Abstract

Purpose

The purpose of this investigation is to determine the nature of the flow field, temperature distribution and heat and mass transfer in a triangular solar collector enclosure with a corrugated bottom wall in the unsteady condition numerically.

Design/methodology/approach

Non-linear governing partial differential equations (i.e. mass, momentum, energy and concentration equations) are transformed into a system of integral equations by applying the Galerkin weighted residual method. The integration involved in each of these terms is performed using Gauss’ quadrature method. The resulting non-linear algebraic equations are modified by the imposition of boundary conditions. Finally, Newton’s method is used to modify non-linear equations into the linear algebraic equations.

Findings

Both the buoyancy ratio and thermal Rayleigh number play an important role in controlling the mode of heat transfer and mass transfer.

Originality/value

Calculations are performed for various thermal Rayleigh numbers, buoyancy ratios and time periods. For each specific condition, streamline contours, isotherm contours and iso-concentration contours are obtained, and the variation in the overall Nusselt and Sherwood numbers is identified for different parameter combinations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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