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RESEARCH PAPERS: Forced Convection

Heat Transfer Studies in the Flow Over Shallow Cavities

[+] Author and Article Information
Paulo S. Zdanski

Department of Mechanical Engineering, State University of Santa Catarina, 89223-000 Joinville, SC, Brazil

M. A. Ortega, Nide G. Fico

Department of Aeronautical Engineering,  Instituto Tecnológico de Aeronáutica, ITA 12228-900, S. J. dos Campos, SP, Brazil

J. Heat Transfer 127(7), 699-712 (Dec 20, 2004) (14 pages) doi:10.1115/1.1924630 History: Received February 05, 2004; Revised December 20, 2004

Fluid flows along a shallow cavity. A numerical study was conducted to investigate the effects of heating the floor of the cavity. In order to draw a broader perspective, a parametric analysis was carried out, and the influences of the following parameters were investigated: (i) cavity aspect ratio, (ii) turbulence level of the oncoming flow, and (iii) Reynolds number. A finite-difference computer code was used to integrate the incompressible Reynolds-averaged Navier–Stokes equations. The code, recently developed by the authors, is of the pressure-based type, the grid is collocated, and artificial smoothing terms are added to control eventual odd–even decoupling and nonlinear instabilities. The parametric study revealed and helped to clarify many important physical aspects. Among them, the so called “vortexes encapsulation,” a desirable effect, because the capsule works well as a kind of fluidic thermal insulator. Another important point is related to the role played by the turbulent diffusion in the heat transfer mechanism.

Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of the flow over a solar collector with wind barriers

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Figure 2

Cavity geometry with the main dimensions

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Figure 3

Cross-sectional profiles of turbulent kinetic energy for the two-dimensional duct

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Figure 4

Comparison of normalized velocity profile with the universal log law

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Figure 5

Comparison of normalized temperature profile with analytical data

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Figure 6

Cross-sectional profiles of turbulent kinetic energy: Grid refinement study

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Figure 7

Two-dimensional duct: Cross-sectional profiles of normalized turbulent kinetic energy

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Figure 8

Two-dimensional duct: Cross-sectional profiles of normalized turbulent kinetic energy dissipation

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Figure 9

Two-dimensional channel with a sudden expansion

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Figure 10

Friction coefficient distribution along the horizontal wall downstream of the step

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Figure 11

Stanton number distributions along the horizontal wall downstream of the step: Comparison of high- and low-Reynolds number solutions

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Figure 12

Typical computational grid with points clustering

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Figure 13

Streamlines for the typical cavity, AR=8. (a) High-Reynolds number turbulence model solution; (b) Low-Reynolds number turbulence model solution.

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Figure 14

Distribution of pressure coefficient along the cavity floor (AR=8)

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Figure 15

Cross-sectional mean temperature profiles: x∕s=1.0, x∕s=3.0, x∕s=5.0, and x∕s=7.0

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Figure 16

(a) Heat transfer rate distribution along the cavity floor; (b) Heat flux due to turbulent fluctuations at a plane parallel to the wall and such that y∕s=0.1

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Figure 17

Streamlines for the cavity with aspect ratio AR=6

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Figure 18

Streamlines for the cavity with aspect ratio AR=12

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Figure 19

Streamlines for the cavity with aspect ratio AR=10

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Figure 20

Horizontal velocity component at the first computational node: (a) AR=8; (b) AR=10

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Figure 21

Turbulent flow in a shallow cavity: aspect ratio influence. (a) Heat flux at the wall (y∕s=0); (b) Heat flux due to turbulent fluctuations at a plane y∕s=0.1.

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Figure 22

Streamlines for the cavity with aspect ratio AR=8: (a) Turbulence level, 4%, (b) Turbulence level, 10%

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Figure 23

Turbulent flow in a cavity with AR=8. Influence of the entrance turbulent level: (a) Heat flux at the wall (y∕s=0); (b) Turbulent heat flux at a plane y∕s=0.1.

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Figure 24

Streamlines for the cavity with aspect ratio AR=8: (a) Res=13,285; (b) Res=31,880

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Figure 25

Turbulent flow in a cavity with AR=8. Influence of the Reynolds number: (a) Heat flux at the wall (y∕s=0); (b) Turbulent heat flux at a plane y∕s=0.1.

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