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Research Papers: Natural and Mixed Convection

Experimental and Numerical Investigation of Turbulent Natural Convection Flow in a Vertical Channel With a Heated Obstacle

[+] Author and Article Information
Yamina Harnane

Assistant Professor
Department of Mechanical,
Faculty of Technology,
University of Batna,
5, Avenue Chahid Boukhlouf,
Batna 05000, Algeria
e-mail: harnane_y@yahoo.fr

Didier Saury

Professor
Pprime Institute,
UPR CNRS 3346,
CNRS-ENSMA-Poitiers University,
Fluid, Thermal and
Combustion Science Department,
ENSMA, Téléport 2,
1, Avenue Clément Ader, BP 40109,
Futuroscope Cedex F-86961, France
e-mail: didier.saury@ensma.fr

Rachid Bessaïh

Professor
Laboratory of Applied Energetic and Pollution,
Department of Mechanical Engineering,
University of Constantine 1,
Aïn El. Bey Road,
Constantine 25000, Algeria
e-mail: bessaih.rachid@gmail.com

Denis Lemonnier

Director of Research at CNRS
Pprime Institute,
UPR CNRS 3346,
CNRS-ENSMA-Poitiers University,
Fluid, Thermal and
Combustion Science Department,
ENSMA, Téléport 2,
1, Avenue Clément Ader, BP 40109,
Futuroscope Cedex F-86961, France
e-mail: denis.lemonnier@ensma.fr

Chérif Bougriou

Professor
Department of Mechanical,
Faculty of Technology,
University of Batna,
5, Avenue Chahid Boukhlouf,
Batna 05000, Algeria
e-mail: cherif_bougriou@yahoo.fr

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received July 25, 2013; final manuscript received July 5, 2014; published online August 5, 2014. Assoc. Editor: Danesh/D. K. Tafti.

J. Heat Transfer 136(10), 102502 (Aug 05, 2014) (15 pages) Paper No: HT-13-1371; doi: 10.1115/1.4028022 History: Received July 25, 2013; Revised July 05, 2014

In the present study, experiments were carried out for natural turbulent convection induced by a heated square bar in a two-dimensional (2D) open vertical channel for different Rayleigh numbers and bar positions. For this purpose, particle image velocimetry (PIV) system has been employed to investigate the velocity field in the vertical center channel plane. The present work is also concerned with computational fluid dynamics (CFD) simulation by employing large Eddy simulation (LES) turbulence model, used in fire dynamic simulation (FDS) code. Calculations were performed for different chimney aspect ratios A* (height Lb over width d) and modified Rayleigh numbers ranging between 4 × 107 and 108. Experimental and numerical results included mean velocity profiles; flow structure and Nusselt number were presented and discussed. To validate CFD code, velocity profiles along channel elevation were compared with our experimental measurements, and a good agreement was observed. Therefore, FDS code is a useful tool to simulate natural turbulent convection dynamic field, and consequently the thermal field in such situation. CFD code has been used to study the best heated bar location (corresponding to the best cooling effect) in the channel as well as the best airflow rate. This best location and its explanation are discussed in this paper.

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References

Figures

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Fig. 1

(a) Flow channel and the coordinate system; (b) experimental device on solid works; and (c) experimental setup

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Fig. 2

Dimensionless divergence of the mean velocity field in the midplane of the channel and a zoom near the square bar

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Fig. 3

Effects of grid size for Ram = 108 and A*= 4 on (a) dimensionless temperature T* at elevation Z*= 2; (b) dimensionless vertical component W at elevation Z*= 2; and (c) Nusselt number along the bottom, top, and left (right) surfaces of the square bar

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Fig. 4

Histogram of numerical results obtained by different teams: (a) Nusselt number on the heated surface of the channel and (b) bulk temperature [28]

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Fig. 5

Measured and calculated mean vertical velocity at different elevations of the channel for Ram = 108 and A*= 4: (a) Z*= 0.5; (b) Z*= 2; (c) Z*= 2.5; and (d) Z*= 4

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Fig. 6

Measured and calculated mean vertical velocity at different elevations of the channel for Ram = 4 × 107 and A*= 4: (a) Z*= 0.5; (b) Z*= 2; (c) Z*= 2.5; and (d) Z*= 4.

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Fig. 7

Comparison between experimental and LES mean vertical velocity along the channel for Ram = 108 and A*= 4

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Fig. 8

Centerline profiles (X*=0.5) for dimensionless mean velocity for Ram = 108 and A*= 4: (a) horizontal component and (b) vertical component

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Fig. 9

A comparison of measured and calculated for Ram = 108 and A*= 4: (a) dimensionless velocity field and (b) stream lines

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Fig. 10

A comparison of measured and calculated contours of mean dimensionless velocity for Ram = 108 and A*= 4 (a) horizontal component and (b) vertical component

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Fig. 11

A comparison of measured and calculated contours of mean dimensionless velocity for Ram = 4 × 107 and A*= 4: (a) horizontal component and (b) vertical component

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Fig. 12

Local Nusselt number profiles along surfaces of the square bar for Ram = 108 and A*= 4: (a) top surface; (b) bottom surface; and (c) left and right surface

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Fig. 13

Local Nusselt number profiles along surfaces of the square bar for Ram = 108 at different locations; A*= 4 (inlet location), A*= 7/6 (outlet location), and A*= 2.5 (center location): (a) top surface; (b) bottom surface; (c) left surface; and (d) right surface

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Fig. 14

Variation of the dimensionless mass flow rate, Q, with vertical bar position for Ram = 108

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