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Soret and Dufour effects on an unsteady MHD flow about a permeable rotating vertical cone with variable fluid properties

Jamir Temjennaro, Konwar Hemanta

Archives of Thermodynamics

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2024

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Vol. 45, no 1

75--86

EN

The objective of the present work is to examine the characteristics of unsteady incompressible magnetohydrodynamic fluid flow around a permeable rotating vertical cone. The effects of thermal radiation, viscous dissipation, and the Soret and Dufour effects are investigated in the analysis of heat and mass transfer. The viscosity of the fluid is considered inversely proportional to the temperature, and the thermal conductivity of the fluid is considered directly proportional to the temperature. The governing equations are converted into ordinary differential equations using suitable similarity transformations, which are then solved numerically using bvp4c from MATLAB. Results obtained in this study are in excellent correlation with previously conducted studies. The results demonstrate that the Dufour and Soret effects subsequently reduce the heat transit rate (by 3.3%) and mass transit rate (by 1.2%) of the system. It is also detected that fluids with higher viscosity tend to increase tangential skin friction (+8.9%) and azimuthal skin friction (+8.3%). The heat transit rate of the system is found to be more efficient for fluids with higher viscosity and lower thermal conductivity and Eckert numbers. Furthermore, the thickness of the momentum, thermal, and concentration boundary layers significantly reduces while the heat and mass transit rates (+17.8% and +18.3%, respectively) of the system become more efficient for greater values of the unsteadiness parameter.

2

Effect of temperature-dependent viscosity on ferroconvection in a porous medium

Ramanathan A., Muchikel N.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 1

93-104

EN

The effect of temperature-dependent viscosity on the threshold of ferroconvective instability in a porous medium is studied using the Brinkman model. It is found that the stationary mode of instability is preferred to the oscillatory mode. The critical values of the magnetic Rayleigh number marking the onset of ferroconvection are obtained using the Galerkin technique. It is found that the effect of magnetization is to destabilize the system and so is the effect of temperature-dependent viscosity. The porous medium is found to have a stabilizing influence on the onset of convection. The problem is important in energy conversion devices involving ferromagnetic fluids as working media.

3

Numerical heat transfer in a rectangular duct for a non-Newtonian fluid with shear rate-dependent thermal conductivity and temperature dependent viscosity

Shin S., Kim B. S.

Applied Mechanics and Engineering

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1998

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Vol. 3, no 2

323-337

EN

The present numerical study investigates the effect of the shear rate-dependent thermal conductivity (SRDC) fluids on the heat transfer enhancement in a 2:1 rectangular duct flow. An axially and peripherally constant heat flux boundary conditions (H2) was adopted for a top-wall-heated configuration. The present numerical results of Nusselt numbers for SRDC fluid show the heat transfer enhancement over those of a shear rate-independent thermal conductivity fluid. The heat transfer enhancement is due to the effect of the increased thermal conductivity near the wall, which is attributed to the thigh wall shear rates. The present study proposes a correlation between the Nusselt number and variable thermal conductivity as follows; ___ . Both the temperature and shear rate-dependencies of the properties play important roles on the heat transfer enhancement.