Effect of surface radiation on RBC in cavities heated from below

Gad, M. Ashish; Balaji, C.

doi:10.1016/j.icheatmasstransfer.2010.08.003

Cited by 22 publications

(13 citation statements)

References 10 publications

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“…In order to make comparisons with the results of Gad and Balaji 0 H/k = 7.765 (i.e. H = 3.14cm to match [1] with T c = T 0 − ∆T /2 and T h = T 0 + ∆T /2). In this study, Navier-Stokes equations of the incompressible flow under the Boussinesq approximation are solved : The radiative heat flux q r is positive when wall radiates more towards other walls than it is irradiated.…”

Section: Governing Equationsmentioning

confidence: 99%

“…Heat transfer in a cavity heated from below has been widely investigated [1]. Nevertheless, few studies with wall radiation have been conducted and the effect of wall radiation is less understood in the litterature.…”

Section: Introductionmentioning

confidence: 99%

“…Also, the given convective and radiative Nusselt numbers are not associated to the top or bottom walls. The effect of vertical wall emissivity (0 V 0.85) and of cavity aspect-ratio (1 AR 10) on Rayleigh-Bénard convection is investigated in Gad and Balaji [1]. The numerical solutions are computed using FLUENT to solve steady incompressible Navier-Stokes equations with radiative walls and a transparent medium.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Wall Radiation in 2d Cavities Heated From Below

Albin¹,

Knikker²,

Xin³

2018

International Heat Transfer Conference 16

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This study investigates numerically the effects of wall radiation on Bénard cells in cavities heated from below using Chebyshev spectral methods. Bifurcation theory is also used to describe and analyse the cellular flow solutions obtained in a square and a rectangle cavities filled with air. As wall radiation modifies the flow via the adiabatic vertical wall condition, the motionless and thermally stratified solution no longer exists at low Rayleigh numbers and is replaced by a very weak 2 × 2 cellular solution. This 4-cell weak flow undergoes pitchfork bifurcations at higher Rayleigh numbers: both perfect and imperfect pitchfork bifurcations are observed in the presence of wall radiation. Bifurcations to cellular flows with a reflection symmetry become imperfect because the cellular flows with the opposite rotating directions are no more equivalent. Therefore the resulting convective and radiative Nusselt numbers of the two bifurcated branches are no longer the same on the top or bottom wall. Note also that Nusselt numbers (either convective or radiative) of any bifurcated branch at one Rayleigh number are different on the bottom and top walls with wall radiation. Results obtained are analysed and some recommendations are given to describe Bénard flows with wall radiation.

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Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Wall Radiation in 2d Cavities Heated From Below

Albin¹,

Knikker²,

Xin³

2018

International Heat Transfer Conference 16

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“…This problem was reconsidered more recently by Gad and Balaji [28] for air-filled, rectangular cavities heated from below with surface radiation spanning six different aspect ratios (from A = 1 to A = 10). The critical Rayleigh number for the onset of convection was determined as function of two parameters: the emissivity of the adiabatic sidewalls and the aspect ratio for a cold top wall at T c = 303 K, the emissivity of the horizontal walls being set to ε = 0.85.…”

Section: Coupled Natural Convection and Surface Radiation In Cavitiesmentioning

confidence: 99%

Effect of surface radiation on natural convective flows and onset of flow reversal in asymmetrically heated vertical channels

Bousetta

Chénier

et al. 2013

International Journal of Thermal Sciences

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To cite this version:R. Li, M. Bousetta, Eric Chénier, Guy Lauriat. Effect of surface radiation on natural convective flows and onset of flow reversal in asymmetrically heated vertical channels. International Journal of Thermal Sciences, Elsevier, 2013, 65 (-), pp.9-27. <10.1016/j.ijthermalsci.2012.10.023>. Effect of surface radiation on natural convective flows and onset of flow reversal in asymmetrically heated vertical channels AbstractNumerical solutions on the influence of surface radiation on the laminar air flow induced by natural convection in vertical, asymmetrically-heated channels are discussed. Variable property effects are accounted for in a full-elliptic mathematical formulation. The density variation is determined from the state equation for ideal gas. The experimental design and data reported in Webb and Hill [1] are taken as the base cases for carrying out the computations. The occurrence of flow reversals is first considered and revisited for pure natural convection, and the Nusselt number correlations derived from the numerical results are favorably compared with those reported in [1]. It is shown that the general effect of surface radiation is to delete the onset of pocketlike recirculations at the top part of the channel, to reduce the heated wall temperatures, and to increase the facing wall temperatures. Comparisons with usual methods used for decoupling the surface radiation effects are discussed. In the range of parameters investigated, increases in differences between inlet and maximum wall temperatures up to 200 K are shown to have small influences on the flow field and negligible effects on heat transfer performances.Keywords: Natural convection, surface radiation, vertical channels, flow reversal, variable property effects, numerical simulations order of consistency of the numerical scheme β thermal coefficient of volumetric expansion,

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“…Bazı çalışmalarda ise, alt duvarından ısıtılmış, üst duvarından soğutulmuş, diğer duvarlarından yalıtılmış kapalı dikdörtgen kutulardaki birleşik ısı transferi incelenmiştir. (Rayleigh-Bernard Problemi) (Ridouane et al 2004, Ridouane et al 2005, Gad and Balaji 2010.…”

Section: Introductionunclassified

Numerical Investigation of Natural Convection and Surface Radiation in an Air Filled Square Enclosure with a Wavy Bottom Wall

Tekkalmaz¹

2018

AKU-J. Sci. Eng.

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Alt duvarı dalgalı ve tüm duvarlarında aynı yüzey ışınım yayma oranına sahip kapalı kare geometride birleşik doğal taşınım ve yüzey ışınımı sayısal olarak incelenmiştir. Geometride alt duvar ısıtılmış, üst duvar soğutulmuş, dikey duvarlar ise yalıtılmıştır. Sıcak ve soğuk duvarlar izotermal ve sabit sıcaklıkta tutulmuştur. Doğal taşınım için tanımlanan momentum ve enerji denklemi 10 4 ≤Ra≤10 6 ve 0≤ε≤1 alınarak SIMPLE algoritması ile sonlu hacimler kullanılarak Fluent paket programında çözülmüştür. Katılımcı olmayan ortam için yüzeyler arası ışınımla ısı transferi denklemi Discrete Ordinate Metod (DOM) kullanılarak çözülmüştür. Soğuk duvar üzerinden hesaplanan ortalama Nusselt sayısı ve geometride meydana gelen akış değişimleri değişen Rayleigh sayısı, yüzey ışınım yayma oranı, alt duvar dalga sayısı ve dalga genliği için analiz edilmiştir. Dalgalı duvarın dalga sayısı ve genliğinin değişimi aynı şartlardaki düz duvara göre bazı durumlarda ortalama toplam Nusselt sayısında maksimum %8.82 değerinde bir iyileştirme sağlamıştır.

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Effect of surface radiation on RBC in cavities heated from below

Cited by 22 publications

References 10 publications

Influence of Wall Radiation in 2d Cavities Heated From Below

Influence of Wall Radiation in 2d Cavities Heated From Below

Effect of surface radiation on natural convective flows and onset of flow reversal in asymmetrically heated vertical channels

Numerical Investigation of Natural Convection and Surface Radiation in an Air Filled Square Enclosure with a Wavy Bottom Wall

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