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Research Papers: Evaporation, Boiling, and Condensation

The Effect of Pore Size on the Heat Transfer Between a Heated Finned Surface and a Saturated Porous Plate

[+] Author and Article Information
M. J. Schertzer

Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L86 4L7, Canada

D. Ewing1

Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L86 4L7, Canada

C. Y. Ching2

Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L86 4L7, Canadachingcy@mcmaster.ca

J. S. Chang

Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, ON, L86 4L7, Canada

1

Present address: Department of Mechanical and Materials Engineering, Queen’s University.

2

Corresponding author.

J. Heat Transfer 131(1), 011501 (Oct 17, 2008) (7 pages) doi:10.1115/1.2977595 History: Received November 30, 2007; Revised April 29, 2008; Published October 17, 2008

An investigation was performed to examine the effect that the pore size in a porous plate had on the heat transfer between a heated finned surface and a saturated porous plate at different gap distances between the surfaces. Experiments were performed for a porous plate with a nominal pore size of 50μm and the results were compared with previous results for a pore size of 200μm (Schertzer, 2006, “The Effect of Gap Distance on the Heat Transfer Performance Between a Finned Surface and a Saturated Porous Plate  ,” Int. J. Heat. Mass Transfer, 4, pp. 4200–4208). The plate with the smaller pore size performed better at small and intermediate gaps but not at large gaps. The maximum heat transfer coefficient was similar for both plates when compared in terms of the ratio between the gap distance and the pore size. However, the temperature distributions on the heated foil and their evolution with heat flux were dissimilar when compared in terms of the gap distance or the gap to pore ratio, suggesting that the boiling dynamics within the gap does not scale with either parameters.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the experimental facility

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Figure 2

SEM images of the surface of the porous plate with a pore size of (a) 50μm and (b) 200μm. A length of 500μm is shown on both images.

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Figure 3

Detailed sketch of the heated fin assembly. The second copper electrode and a portion of the horizontal rails have been removed for clarity.

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Figure 4

Change in (a) the average foil temperature and (b) the average heat transfer coefficient as a function of heat flux for gap distances of ◇ ◆ G=0μm, ▲ △ G=300μm ● ○ G=500μm, and ◼ ◻ G=900μm. The solid symbols are for the RP=50μm plate, and the open symbols are for the RP=200μm plate (15).

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Figure 5

Change in the average foil temperature as a function of heat flux for gap distances of ◇ ◆ G=0μm, ● ○ G=100μm, ◼ ◻ G=200μm, and ▲ △ 300μm. The solid symbols are for the RP=50μm plate, and the open symbols are for the RP=200μm plate (15).

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Figure 6

Change in the maximum heat transfer coefficient as a function of (a) gap distance and (b) the ratio of the gap distance to pore radius for ◼ the RP=50μm plate and ◻ the RP=200μm plate.

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Figure 7

Typical transients of the instantaneous temperature (°C) distribution on the heated foil for the RP=50μm plate with G=0μm at a heat flux of 15kW∕m2. These images were recorded 17ms apart.

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Figure 8

Time and space averaged probability density functions of the temperature on the foil surface for (a) the RP=50μm plate and (b) the RP=200μm plate with G=0μm at q″= — 15, –– 20 and ⋯ 25kW∕m2.

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Figure 9

Time and space averaged probability density functions of the temperature on the foil surface for (a) the RP=50μm plate and (b) the RP=200μm plate with G=100μm at q″= — 20, ––30 and ⋯ 50kW∕m2.

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Figure 10

Time and space averaged probability density functions for the RP=50μm plate (left) and the RP=200μm plate (right). The results for gap to pore ratio of (a) 2 for q″= — 15kW∕m2, – – 20kW∕m2, ⋯ 30kW∕m2, — 40kW∕m2, and – – 50kW∕m2, (b) 4 for q″= — 20kW∕m2, – – 30kW∕m2, ⋯ 40kW∕m2, — 90kW∕m2, and – – 135kW∕m2, (c) 6 for q″= — 40kW∕m2, – – 60kW∕m2, ⋯ 90kW∕m2, — 125kW∕m2, and – – 160kW∕m2, (d) 2.5 for q″= — 60kW∕m2, – – 80kW∕m2, ⋯ 130kW∕m2, — 180kW∕m2, and – – 200kW∕m2 (e) 3.5 for q″= — 120kW∕m2, – – 160kW∕m2, ⋯ 200kW∕m2, — 220kW∕m2, and – – 240kW∕m2, and (f) 4.5 for q″= — 100kW∕m2, – – 120kW∕m2, ⋯ 200kW∕m2, — 220kW∕m2, and – – 230kW∕m2.

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Figure 11

Time and space averaged probability density functions for the RP=500μm plate (left) and the RP=200μm plate (right). The results for (a) G=300μmq″= — 40kW∕m2, – – 60kW∕m2, ⋯ 90kW∕m2, — 125kW∕m2, and – – 160kW∕m2 (b) G=500μm for q″= — 90kW∕m2, – – 120kW∕m2, ⋯ 150kW∕m2, — 180kW∕m2, and – – 190kW∕m2, (c) G=900μm for q″= — 40kW∕m2, – – 90kW∕m2, ⋯ 120kW∕m2, — 150kW∕m2, and – – 180kW∕m2, (d) G=300μm for q″= — 30kW∕m2, – – 60kW∕m2, ⋯ 80kW∕m2, — 100kW∕m2, and – – 110kW∕m2, (e) G=500μm for q″= — 60kW∕m2, –– 80kW∕m2, ⋯ 130kW∕m2, — 180kW∕m2, and – –200kW∕m2 and (f) G=900μm for q″= — 100kW∕m2, – – 120kW∕m2, ⋯ 200kW∕m2, — 220kW∕m2, and – – 230kW∕m2.

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Figure 12

Typical transients of the instantaneous temperature (°C) distribution on the heated foil for the RP=50μm plate when (a) G=300 and q″=160kW∕m2 and when (b) G=900μm and q″=180kW∕m2. The images were recorded 17ms apart.

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