Effects of Reynolds and Prandtl numbers on heat transfer from a square cylinder in the unsteady flow regime

Sahu, Akhilesh K.; Chhabra, R.P.; Eswaran, V.

doi:10.1016/j.ijheatmasstransfer.2008.07.032

Cited by 93 publications

(38 citation statements)

References 22 publications

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“…Em Sahu et al [3], foram analisados os efeitos dos números de Prandtl e Reynolds no comportamento fluidodinâmico e na transferência de calor para escoamento externo em um cilindro quadrado e em Catalano et al [4] foi analisado o escoamento sobre um cilindro com elevados números de Reynolds.…”

Section: Gmbarros Et Al Scientiaunclassified

Influência da Convecção Mista sobre a Otimização Geométrica de um Arranjo Triangular de Cilindros em Escoamentos Laminares

et al. 2015

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Este estudo numérico consiste em avaliar a forma geométrica de um arranjo triangular de cilindros submetidos a escoamentos transientes, bi-dimensionais, incompressíveis, laminares e com convecção mista por meios do Constructal Design. As simulações foram realizadas para escoamentos com números de Reynolds e Prandtl, de 100 e 0,71, respectivamente, avaliando-se três diferentes números de Richardson: Ri = 0,1; 1,0; e 10,0. This numerical study is to evaluate the geometric shape of a triangular arrangement of cylinders subjected to transient flows, two-dimensional, incompressible, laminar and mixed convection by means of Constructal Design. The simulations were performed for Reynolds and Prandtl numbers, 100 and 0.71, respectively, evaluating three different numbers of Richardson: Ri = 0.1; 1.0; and 10.0. The mass conservation equations, momentum and energy were solved using the finite volume method (FVM -English: Finite Volume Method). The area occupied by the cylinder is a geometric constraint problem. The main objective is to evaluate the influence of Ri in the effect of the ratio S T /D (cross step on the diameter) on the drag coefficient (C D ) and the Nusselt number (Nu D ) between the cylinders and the surrounding flow, and obtain the optimal geometry of the multi-objective problem. In all cases studied the ratio S L /D (on the longitudinal pitch diameter) was fixed S L /D = 1.5. It was estimated that the variation of the driving mechanism of the flow (caused by the variation of Richardson number) have affected the C D magnitudes and Nu D .Keywords: Arrange of Cylinders, Geometrical Optimization, Mixed Convection INTRODUÇÃOSistemas térmicos em problemas que envolvem interações entre um escoamento de fluido e superfícies são amplamente estudados e empregados em diversas áreas da engenharia. Os escoamentos externos sobre cilindros, em especial, representam de forma simplificada diversos problemas de engenharia como pontes, torres, conversores de energia eólica, condensadores,

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Section: Gmbarros Et Al Scientiaunclassified

Influência da Convecção Mista sobre a Otimização Geométrica de um Arranjo Triangular de Cilindros em Escoamentos Laminares

et al. 2015

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“…Based on a combination of numerical, theoretical and experimental studies, different flow regimes for the square cylinder have been identified in the literature depending upon the value of the Reynolds number and Prandtl number (A. Sohankar, 1995;Bhattacharyya and Mahapatra, 2005;Breuer, Bernsdorf, Zeiser, and Durst, 2000;Dhiman, Chhabra, and Eswaran, 2005;Dhiman, Chhabra, Sharma, and Eswaran, 2006;Gupta, Sharma, Chhabra, and Eswaran, 2003;Ji, Kim, and Hyun, 2008;Rahnama and Hadi-Moghaddam, 2005;Sahu, Chhabra, and Eswaran, 2009;Eswaran, 2004a, 2004b;Sheard, Fitzgerald, and Ryan, 2009;Sohankar, Norberg, and Davidson, 1998;Wei-Bin, Neng-Chao, Bao-Chang, and ZhaoLi, 2003). The main flow regimes reported to date are: a creeping flow region in which no flow separation takes place at the surface of the cylinder (Re≤1).…”

Section: Introductionmentioning

confidence: 99%

“…The effect of the Prandtl number on the heat transfer from unconfined and confined square cylinders has been also studied (Dhiman et al, 2005;Dhiman et al, 2006;Gupta et al, 2003); but are limited to the steady flow regime (Re up to 40). A numerical study of the effects of the Reynolds and Prandtl numbers on the rate of heat transfer from a square cylinder for the range of conditions Re 60 to 160 and Pr 0.7 to 50 has been studied (Sahu et al, 2009). The effect of confinement on flow and heat transfer of the forced and mixed convection regimes from a square cylinder placed in a channel has been reported in the literature (Rahnama and HadiMoghaddam, 2005).…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis and Prediction of Unsteady Forced Convection over a Sharp and Rounded Edged Square Cylinder

Dey¹,

Das²

2016

JAFM

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An unsteady two-dimensional forced convection over a square cylinder with sharp and rounded corner edge is numerically analyzed for the low Reynolds number laminar flow regime. In this study, the analysis is carried out for Reynolds number (Re) in the range of 80 to 180 with Prandtl number (Pr) variation from 0.01 to 1000 for various corner radius (r=0.50, 0.51, 0.54, 0.59, 0.64 and 0.71). The lateral sides of the computational domain are kept constant to maintain the blockage as 5%. Heat transfer due to unsteady forced convection has been predicted by Artificial Neural network (ANN). The present ANN is trained by the input and output data which has been acquired from the numerical simulation, performed in finite volume based Computational Fluid Dynamics (CFD) commercial software FLUENT. The heat transfer characteristics over the sharp and rounded corner square cylinder are evaluated by analyzing the local Nusselt number (Nu local ), average Nusselt number (Nu avg ) at various Reynolds number, Prandtl numbers and for various corner radii. It is found that the heat transfer rate of a circular cylinder can be enhanced by 12% when Re is varying and 14% when Prandtl number is varying by introducing a new cylinder geometry of corner radius r=0.51. It is found that the unsteady forced convection heat transfer over a cylinder can be predicted appropriately by ANN. It is also observed that the back propagation ANN can predict the heat transfer characteristics of forced convection very quickly compared to a standard CFD method.

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“…Based on a combination of numerical, theoretical and experimental studies, different flow regimes for the square cylinder have been identified in the literature depending upon the value of the Reynolds number and Prandtl number [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The main flow regimes reported to date are: a creeping flow region in which no flow separation takes place at the surface of the cylinder (Re 1).…”

Section: Introductionmentioning

confidence: 99%

“…The forced and mixed convection flow and heat transfer from a square cylinder placed in a channel have been reported to study the effect of confinement [8]. A numerical study of the rate of heat transfer over a square cylinder for different Re and Pr in the range of Re, 60-160 and Pr, 0.7-50 has been studied [9]. In recent years, some researchers [10,11] studied the fluid flow and heat transfer features from a square cylinder in the both steady and unsteady flow regimes for the Re above 160 and for two different boundary conditions applied to the cylinder surface that are isothermal and constant heat flux boundary.…”

Section: Introductionmentioning

confidence: 99%

Development of GEP and ANN model to predict the unsteady forced convection over a cylinder

Dey

Sarkar

2015

Neural Comput & Applic

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In the present study, forced convection heat transfer flow past a square cylinder with a rounded corner edge in an unsteady two-dimensional low Reynolds number laminar regime is numerically performed and predicted by the artificial neural network (ANN) and gene expression programming (GEP). In this study, Reynolds number (Re) is varied from 80 to 180 with Prandtl number (Pr) variation from 0.01 to 1000 for various corner radii (r = 0.50, 0.51, 0.54, 0.59, 0.64 and 0.71). Finite volume-based commercial software FLUENT is used in the present numerical solution for the output results that are used to train the present ANN and GEP model. The local Nusselt number (Nu local ) and average Nusselt number (Nu avg ) at various Reynolds numbers, Prandtl numbers and various corner radii are utilized to forecast the heat transfer characteristics. It is found that the heat transfer rate of a circular cylinder can be enhanced by 12 % when Re is varying and 14 % when the Prandtl number is varying by introducing new cylinder geometry of corner radius r = 0.51. The forced convection characteristics can be envisioned properly and very promptly by using back-propagation ANN and GEP in contrast to a regular CFD approach. It is also found that GEP is more efficient in predicting than the ANN. The outcomes obtained by the present numerical study confirm a fine accord with the available results in the literature.

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Effects of Reynolds and Prandtl numbers on heat transfer from a square cylinder in the unsteady flow regime

Cited by 93 publications

References 22 publications

Influência da Convecção Mista sobre a Otimização Geométrica de um Arranjo Triangular de Cilindros em Escoamentos Laminares

Influência da Convecção Mista sobre a Otimização Geométrica de um Arranjo Triangular de Cilindros em Escoamentos Laminares

Numerical Analysis and Prediction of Unsteady Forced Convection over a Sharp and Rounded Edged Square Cylinder

Development of GEP and ANN model to predict the unsteady forced convection over a cylinder

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