Mixed convection in the presence of horizontal impermeable surfaces in saturated porous media with variable permeability

Chandrasekhara, B. C.

doi:10.1007/bf01403756

Cited by 37 publications

(10 citation statements)

References 8 publications

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“…In some applications, such as fixed-bed catalytic reactors, packed bed heat exchangers and drying, the porosity is not uniform but has a maximum value at the wall and a minimum value away from the wall. This wall-channeling phenomenon has been reported by a number of investigators such as Vafai [6], Chandrasekhara et al [7], Chandrasekhara [8], and Hong et al [9] for forced, natural, and mixed convection boundary layer flows adjacent to a horizontal and vertical surfaces. It is shown that the variable porosity effect increases the temperature gradient adjacent to the wall resulting in the enhancement of the surface heat flux.…”

Section: Introductionsupporting

confidence: 60%

Variable permeability effect on vortex instability of a horizontal natural convection flow in a saturated porous medium with variable wall temperature

2003

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A linear stability theory is used to analyze the vortex instability of free convection boundary layer flow in a saturated porous medium adjacent to a horizontal surface where the wall temperature is a power function of the distance from the origin. The variation of permeability in the vicinity of the solid boundary is approximated by an exponential function. The variation rate itself depends slowly on the streamwise coordinate, such as to allow the problem to possess a set of solutions, invariant under a group of transformations. Velocity and temperature profiles as well as local Nusselt number for the base flow are presented for the uniform permeability UP and variable permeability VP cases. The critical Rayleigh numbers and the associated wave numbers are obtained for both UP and VP cases. It is found that the variable permeability effect tends to increase the heat transfer rate and destabilize the flow to the vortex mode of disturbance.

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Section: Introductionsupporting

confidence: 60%

Variable permeability effect on vortex instability of a horizontal natural convection flow in a saturated porous medium with variable wall temperature

2003

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“…In some applications, such as fixed-bed catalytic reactors, packed bed heat exchangers, and drying, the porosity is not uniform but has a maximum value at the wall and a minimum value away from the wall. This wall-channeling phenomenon has been reported by a number of investigators, such as Vafai [6], Chandrasekhara [7], Hassanien and Elaiw [8]. It is shown that the variable porosity effect increases the temperature gradient adjacent to the wall, resulting in the enhancement of the surface heat flux.…”

Section: Introductionsupporting

confidence: 57%

“…The effect of the non-uniform temperature profile on the wall is also studied, and corresponds to variations of the parameter m. Moreover, the effect of the inclination angle φ is studied. For the purpose of numerical integration we have assumed d = 1.5, d * = 3, ε ∞ = 0.4, σ = 2 (Chandrasekhara [7]).…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

Vortex instability of mixed convection boundary layer flow adjacent to a non‐isothermal inclined surface in a porous medium with variable permeability

Ełaiw

2008

Z Angew Math Mech

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A linear stability theory is used to analyze the vortex instability of mixed convection boundary layer flow over an inclined heated surface in a porous medium with variable permeability. The variation of permeability in the vicinity of the solid boundary is approximated by an exponential function. The variation rate itself depends slowly on the streamwise coordinate, such as to allow the problem to possess a set of solutions, invariant under a group of transformations. The surface temperature is assumed to vary as a power function of the distance from the origin. In the main flow analysis, both the streamwise and normal component of the buoyancy force are retained in the momentum equations. The present formulation permits the angles of inclination ranging from 0 to close to 90 degrees from the horizontal. Local Nusselt number is presented for the uniform permeability (UP) and variable permeability (VP) cases. The critical Peclet numbers and the associated wave numbers are obtained for both the UP and VP cases. It is found that the VP effect tends to increase the heat transfer rate and destabilize the flow to the vortex mode of disturbance.

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“…It is found from the Table 1 that the thickness A of the second boundary layer is always greater than the thickness of the first boundary layer 6 since ~ is greater than unity for all values of B. The values of B, the dimensionless porous parameter are kept low since the permeability at the wall increases due to the packing of the particles (see Chandrasekhara and Votmeyer [6], Benenati and Brosilow [7] Chandrasekhara et al [8], Chandrasekhara [9] and Chandrasekhara and Namboodiri [10]. However, it is observed from the results that the value of 4 does not …”

Section: --2at +A~o~176 B~-o~mentioning

confidence: 97%

Composite heat transfer in case of steady laminar flow of a gray fluid with large optical density past a horizontal plate embedded in a saturated porous medium

Chandrasekhara

Nagaraju²

1988

Wärme- und Stoffübertragung

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Abstract. The present paper discusses the problem of composite heat transfer and viscous friction of a moving gray medium with large optical density. Expressions for temperature and velocity distributions and the ratio of the radiative component to convective component of heat flux are obtained. It is observed that for a given value of B the ratio of radiative heat flux to convective heat flux is maximum at the edge of the boundary layer and tends to an asymptotic value as the boundary is reached. However, for a given value of K 6, the ratio of heat fluxes increases with increase in B (the porous parameter). The results also show that as the wall temperature approaches the value of free stream temperature, the ratio of heat fluxes decreases. Wiirmeiibergang eines Fluids mit groBer optiseher Dichte bei stationiirer laminarer Str6mung an einer horizontalen Platte eingebettet in einem gesiittigten por~isen MediumZusammenfassung. In der vorliegenden Arbeit wird das Problem des W/irmefibergangs und der viskosen Reibung eines bewegten grauen Mediums mit groger optischer Dichte er6rtert. Man erhfilt Formelausdrficke ffir Temperatur-und Geschwindigkeitsverteilungen und das Verhfiltnis yon dem Anteil der Strahlung zum konvektiven Anteil des Wfirmeflusses. Ffir einen gegebenen Wert yon B (dem por6sen Parameter) beobachtet man, dab das Verhfiltnis des Wfirmestroms durch Strahlung zum konvektiven W/irmestrom am Rand der Grenzflfiche maximal wird und sich dem Wert der Grenzfl/iche asymptotisch n/ihert. Jedoch erh6ht sich bei gegeOenem Wert yon K 6 das Verhfiltnis der Wfirmestr6me mit steigendem B. Die Ergebnisse zeigen auch, dab sich das Verhfiltnis der W/irmestr6me verringert, wenn die Wandtemperatur sich der Temperatur der freien Str6mung nfihert.

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Mixed convection in the presence of horizontal impermeable surfaces in saturated porous media with variable permeability

Abstract: Abstract. Boundary layer approximation is applied for mixed

Cited by 37 publications

References 8 publications

Variable permeability effect on vortex instability of a horizontal natural convection flow in a saturated porous medium with variable wall temperature

Variable permeability effect on vortex instability of a horizontal natural convection flow in a saturated porous medium with variable wall temperature

Vortex instability of mixed convection boundary layer flow adjacent to a non‐isothermal inclined surface in a porous medium with variable permeability

Composite heat transfer in case of steady laminar flow of a gray fluid with large optical density past a horizontal plate embedded in a saturated porous medium

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