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Research Papers: Natural and Mixed Convection

# Flow and Heat Transfer of Natural Convection in Horizontal Annulus With a Heating Element on Inner Cylinder

[+] Author and Article Information
C. S. Yang1

Department of Computer Science and Information Engineering, Far East University, Hsin-Shih, Tainan County 744, Taiwan

D. Z. Jeng, U. H. Tang

Institute of Aeronautics and Astronautics and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwan

C. Gau1

Institute of Aeronautics and Astronautics and Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 70101, Taiwangauc@mail.ncku.edu.tw

1

Corresponding author.

J. Heat Transfer 131(8), 082502 (Jun 04, 2009) (6 pages) doi:10.1115/1.3109995 History: Received August 15, 2008; Revised December 03, 2008; Published June 04, 2009

## Abstract

Experiments have been performed to study natural convection flow and heat transfer in a horizontal annulus when a square heating element is positioned at different locations on the inner insulated cylinder. The annulus is filled with water and has cylinder to cylinder diameter ratio of 3. The square heating element is small and has the width to annulus gap width ratio of 1/6. The range of Rayleigh number studied is approximately from $1.9×106$ to $3.3×107$. It has been found that the flow pattern, the temperature distribution around the inner cylinder wall, and the local heat transfer rate around the outer cylinder are very sensitive to the location of the heating element. The heating element Nusselt numbers at various locations on the inner cylinder are obtained and well correlated against the Rayleigh number to the 1/3 powers. A maximum in the correlation parameter $C$ is obtained when the heating element is placed 90 deg from the bottom.

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## Figures

Figure 4

Temperature distribution around the inner cylinder with heating element positioned at different angles

Figure 5

Nusselt number results and correlation against Rayleigh number with heating element at θh=120 deg

Figure 6

Effect of the heating element position on the heat transfer correlation parameter C

Figure 1

Schematic of test apparatus: (1) outer cylinder, (2) inner cylinder, (3) heating element, (4) cooling coil, (5) thermocouples, (6) insulation, and (7) plexiglass box

Figure 2

Flow pattern with heating element positioned at different angles: (a) θh=0, (b) θh=60 deg, (c) θh=90 deg, (d) θh=120 deg, and (e) θh=180 deg for Ra=1.113×106

Figure 3

Local Nusselt number around the outer cylinder with heating element positioned at different angles

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