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Entropy analysis of third-grade MHD convection flows from a horizontal cylinder with slip

100%

Madhavi K. , Prasad V. R. , Gaffar S. A. , Venkatadri K.

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tom Vol. LXV, nr 3

417--440

EN

In thermos ﬂuid dynamics, free convection ﬂows external to diﬀerent geometries, such as cylinders, ellipses, spheres, curved walls, wavy plates, cones, etc., play major role in various industrial and process engineering systems. The thermal buoyancy force associated with natural convection ﬂows can play a critical role in determining skin friction and heat transfer rates at the boundary. In thermal engineering, natural convection ﬂows from cylindrical bodies has gained exceptional interest. In this article, we mathematically evaluate an entropy analysis of magnetohydrodynamic third-grade convection ﬂows from permeable cylinder considering velocity and thermal slip effects. The resulting non-linear coupled partial diﬀerential conservation equations with associated boundary conditions are solved with an eﬃcient unconditionally stable implicit ﬁnite diﬀerence Keller-Box technique. The impacts of momentum and heat transport coeﬃcients, entropy generation and Bejan number are computed for several values of non-dimensional parameters arising in the ﬂow equations. Streamlines are plotted to analyze the heat transport process in a two-dimensional domain. Furthermore, the deviations of the ﬂow variables are compared with those computed for a Newtonian ﬂuid and this has important implications in industrial thermal material processing operations, aviation technology, diﬀerent enterprises, energy systems and thermal enhancement of industrial ﬂow processes.

2

MHD free convection-radiation interaction in a porous medium - part I: numerical investigation

75%

Vasu B. , Gorla R. S. R. , Murthy P. V. S. N. , Prasad V. R. , Bég O. A. , Siddiqa S.

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tom Vol. 25, no. 1

198--218

EN

A numerical investigation of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a non-Darcy porous medium is presented by taking into account the Soret/Dufour effects. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. We use simple central difference derivatives and averages at the mid points of net rectangles to get finite difference equations with a second order truncation error. We have conducted a grid sensitivity and time calculation of the solution execution. Numerical results are obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters. The dependency of the thermophysical properties has been discussed on the parameters and shown graphically. The Darcy number accelerates the flow due to a corresponding rise in permeability of the regime and concomitant decrease in Darcian impedance. A comparative study between the previously published and present results in a limiting sense is found in an excellent agreement.

3

MHD free convection-radiation interaction in a porous medium - part II: soret/dufour effects

75%

Vasu B. , Gorla R. S. R. , Murthy P. V. S. N. , Prasad V. R. , Beg O. A. , Siddiqa S.

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tom Vol. 25, no. 2

157--175

EN

This paper is focused on the study of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a non-Darcy porous medium by taking into account of the Soret/Dufour effects. The boundary layer equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. Numerical results are obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters, namely the buoyancy ratio parameter, Prandtl number, Forchheimer number, magnetohydrodynamic body force parameter, Soret and Dufour numbers. The dependency of the thermophysical properties has been discussed on the parameters and shown graphically. Increasing the Forchheimer inertial drag parameter reduces velocity but elevates temperature and concentration. Increasing the Soret number and simultaneously reducing the Dufour number greatly boosts the local heat transfer rate at the cylinder surface. A comparative study of the previously published and present results in a limiting sense is made and an excellent agreement is found between the results.