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RESEARCH PAPERS: Natural and Mixed Convection

Localized Heat Transfer in Buoyancy Driven Convection in Open Cavities

[+] Author and Article Information
Wilson Terrell1

Department of Engineering Science, Trinity University, One Trinity Place, San Antonio, TX 78212-7200wilson.terrelljr@trinity.edu

Ty A. Newell

Air Conditioning and Refrigeration Center, Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign, 140 MEB, MC-244, 1206 West Green Street, Urbana, IL 61801

1

Corresponding author.

J. Heat Transfer 129(2), 167-178 (Aug 16, 2006) (12 pages) doi:10.1115/1.2401615 History: Received January 27, 2005; Revised August 16, 2006

Background. An experimental study of buoyancy driven convection heat transfer in an open cavity was conducted. Method of Approach. Test cavities were constructed with calorimeter plates bonded to Styrofoam insulation. The inside of the cavities was heated and then exposed to ambient air for approximately thirty minutes. Different size cavities were examined at inclination angles of 0, 45, and 90deg. The heat transfer coefficient was determined from an energy balance on each calorimeter plate. The cavity’s plate temperatures varied spatially due to the transient nature of the tests. A parameter describing the nonisothermal cavity wall temperature variation was defined in order to compare with isothermal cavity heat transfer results. Results. Results showed that the cavity Nusselt number, based on a cavity averaged temperature, was insensitive to the transient development of nonisothermal conditions within the cavity. Comparison of cavity-average Nusselt number for the current study, where the Rayleigh number ranged from 5×106 to 2×108, to data from the literature showed good agreement. Cavity-average Nusselt number relations for inclination angles of 0, 45, and 90deg in the form of NuH,cav=CRa13 resulted in coefficients of 0.091, 0.105, 0.093, respectively. The 45deg inclination angle orientation yielded the largest Nusselt numbers, which was similar to previous literature results. Trends in the local plate Nusselt numbers were examined and found similar to data from the literature.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Open cavity geometry and orientation

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Figure 2

Photos of various test cavities (from left to right): one-plate per wall, four-plate per wall, and nine-plate per wall

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Figure 3

Nomenclature of wall descriptions at various inclination angles (a) 0, (b) 45, and (c) 90deg

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Figure 4

Schematic of network representation used to examine thermal effects of the insulation

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Figure 5

Plate Nusselt numbers: one-plate per wall cavity with different initial cavity temperatures (Tcav,i) at 0deg inclination angle: (a) plate-1 (ceiling), (b) plate-2 (floor), (c) plate-3 (left wall), (d) plate-4 (right wall), (e) plate-5 (backwall), and (f) spatial temperature deviation of a cavity, ΓT

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Figure 6

Cavity-average Nusselt numbers 0deg inclination angle: (a) current study compared to investigators with studies of open cavities with backwall heated and (b) current study compared to investigators with studies of open cavities with bottom, back, and top walls heated

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Figure 7

Cavity-average Nusselt numbers for inclination angles (a) 45deg and (b) 90deg

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Figure 9

Plate Nusselt numbers: four-plate per wall cavity at 0deg inclination angle (RaH∼9.45×107)

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Figure 10

Plate Nusselt numbers: nine-plate per wall cavity at 0deg inclination angle (RaH∼2.46×108): (a) ceiling, (b) floor, (c) left wall, (d) backwall, and (e) right wall

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Figure 11

Plate Nusselt numbers: one-plate per wall cavity at 45deg inclination angle (RaH∼9.41×106)

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Figure 13

Plate Nusselt numbers: nine-plate per wall cavity at 45deg inclination angle (RaH∼2.53×108): (a) downward-facing wall, (b) upward-facing wall, (c) left wall, (d) base, and (e) right wall

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Figure 14

Plate Nusselt numbers: one-plate per wall cavity at 90deg inclination angle (RaH∼1.13×107)

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Figure 15

Plate Nusselt numbers: four-plate per wall cavity at 90deg inclination angle (RaH∼7.27×107)

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Figure 16

Plate Nusselt numbers: nine-plate per wall cavity at 90deg inclination angle (RaH∼2.57×108): (a) sidewall 1, (b) sidewall 2, (c) sidewall 3, (d) sidewall 4, and (e) base

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Figure 17

Possible flow patterns in cavity, based on local Nusselt numbers of the current study, for various inclination angles: (a) 0deg, (b) 45deg, and (c) 90deg

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Figure 12

Plate Nusselt numbers: four-plate per wall cavity 45deg inclination angle (RaH∼7.61×107)

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Figure 8

Plate Nusselt numbers: one-plate per wall cavity at 0deg inclination angle (RaH∼1.18×107)

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