Search results

The purpose of this work is to highlight the effects of partial unipolar injection on electro-thermo-convection (ETC) in dielectric liquid contained between two eccentric cylinders.

A finite volume method was used to solve governing equations. The study is performed for different parameters, such as radius ratio (0.2 ≤ Γ ≤ 0.6), dimensionless electric Rayleigh number (0 ≤ T ≤ 900), eccentricity (−0.4 ≤ e ≤ 0.4) and thermal Rayleigh number (10 ≤ Ra ≤ 5.105).

It is found that heat transfer increases with increase in dimensionless electric Rayleigh number and eccentricity ratio.

The originality of this work is to analyze the ETC in dielectric liquid subjected to partial unipolar injection between two eccentric cylinders

The effect of radiation on unsteady natural convection in a two‐dimensional participating medium between two horizontal concentric and vertically eccentric cylinders is investigated numerically. The equations of transfer are written by using a bicylindrical coordinates system, the stream function, and the vorticity. The finite volume radiation solution method and the control volume approach are used to discretize the coupled equations of radiative transfer, momentum, and energy. Original results are obtained for three eccentricities, Rayleigh number equal to 10⁴, 10⁵, and a wide range of radiation‐conduction parameter. The effects of optical thickness, wall emissivity, and scattering on flow intensity and heat transfer are discussed.

To provide a finite volume code, based on Cartesian coordinates, for studying combined conductive and radiative heat transfer in three‐dimensional irregular geometries.

In the present study, a three‐dimensional blocked‐off‐region procedure was presented and implemented in a numerical code based on the finite volume method to model combined conductive and radiative heat transfer in complex geometries. This formulation was developed and tested in three‐dimensional complex enclosures with diffuse reflective surfaces and containing gray absorbing‐emitting and isotropically scattering medium. This approach was applied to analyze the effect of the main of thermoradiative parameters on the temperature and flux values for three‐dimensional L‐shaped enclosure.

The proposed isotropic model leads to satisfactory solutions with comparison to reference data, which entitles us to extend it to anisotropic diffusion cases or to non‐gray media. The blocked‐off‐region procedure traits both straight and curvilinear boundaries. For curved or inclined boundaries, a fine or a non‐uniform grid is needed.

This paper offers a simple Cartesian practical technique to study the combined conductive and radiative heat transfer in three‐dimensional complex enclosures with both straight and curvilinear boundaries.

The purpose of this paper is to examine numerically the three natural convection of air induced by temperature difference between a cold outer cubic enclosure and a hot inner cylinder. Simulations have been carried out for Rayleigh numbers ranging from 103 to 107 and titled angle of the enclosure from 0° to 90°. The developed mathematical model is governed by the coupled equations of continuity, momentum and energy, and is solved by finite volume method. The effects of cylinder inclination and Rayleigh number on fluid flow and heat transfer are presented. The distribution of isocontours of temperature and isosurfaces of velocity eventually reaches a steady state in the range of Rayleigh numbers between 103 and 107 for titled inclination of 90°; however, for the remaining inclinations, Rayleigh number must be in the range 103-106 to avoid unsteady state, which is manifested by the division of the area containing the maximum local heat transfer rate into three parts for a Rayleigh number equal to 107 and an inclination of 90°. We mention that instability study is not included in the present paper, which is solely devoted to three-dimensional calculations. Results also indicate that optimal average heat transfer rate is obtained for both high Rayleigh number of 106 and high inclination of 90° for the two cases of the inner cylinder and cubical enclosure.

The manuscript deals with prediction of the three-dimensional natural convection phenomena in a cubical cavity induced by an isothermal cylinder at the center with different inclinations by simulating the flow using highly numerical methods such as finite volume method.

It is found that the local Nusselt number through active walls for titled inclination set at 90°, the symmetry of the flow is conserved and the area containing the maximum heat transfer is divided into three smaller areas situated near the upper portion of the wall, taking the maximum value. That may be due to the preparation of local occurrence of instabilities and bifurcation phenomena that appear for Ra > 107, which is not included in the present paper to save journal space. It was found also that an optimal heat transfer appears when the cylinder orientation becomes vertical (a = 90°). For this inclination, buoyancy forces act upward, corresponding to an aiding situation. In addition, heat transfer rate is increasing with Rayleigh numbers, so correlations of average Nusselt through the cubical cavity and the cylinder are established as function of two parameters (Ra, a). Comparisons of the numerical results with those obtained from all correlations show good agreements.

To the author’s knowledge, studies have thus far adressed three-dimensional cuboids enclosures induced by an inner shape which the location is changed. However, no study has examined three-dimensional natural convection between the inner isothermal cylinder and outer cooled cubical enclosure when the outer enclosure is tilted.