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Research Papers: Evaporation, Boiling, and Condensation

Heat Transport Capability and Fluid Flow Neutron Radiography of Three-Dimensional Oscillating Heat Pipes

[+] Author and Article Information
B. Borgmeyer, C. Wilson, R. A. Winholtz

Department of Mechanical and Aerospace Engineering, University of Missouri-Columbia, Columbia, MO 65201

H. B. Ma1

Department of Mechanical and Aerospace Engineering, University of Missouri-Columbia, Columbia, MO 65201mah@missouri.edu

D. Jacobson, D. Hussey

 National Institute of Standards and Technologies, 100 Bureau Drive, Gaithersburg, MD 20899

Certain trade names and company products are mentioned in the text or identified in an illustration in order to adequately specify the experimental procedure and equipment used. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best available for the purpose.

1

Corresponding author. Present address: Department of Mechanical and Aerospace Engineering, University of Missouri-Columbia, Columbia, MO 65211.

J. Heat Transfer 132(6), 061502 (Mar 31, 2010) (7 pages) doi:10.1115/1.4000750 History: Received May 20, 2009; Revised November 10, 2009; Published March 31, 2010; Online March 31, 2010

An experimental investigation into the parameters affecting heat transport in two three-dimensional oscillating heat pipes (OHPs) was implemented. A three-dimensional OHP is one in which the center axis of the circular channels containing the internal working fluid do not lie in the same plane. This novel design allows for more turns in a more compact size. The OHPs in the current investigation is made of copper tubings (3.175 mm outside diameter, 1.65 mm inside diameter) wrapped in a three-dimensional fashion around two copper spreaders that act as the evaporator and condenser. The two OHPs have 10 and 20 turns in both the evaporator and condenser. The 20-turn OHP was filled to 50% of the total volume with a high performance liquid chromatography grade water. Transient and steady state temperature data were recorded at different locations for various parameters. Parameters such as heat input, operating temperature, and filling ratio were varied to determine its effect on the overall heat transport. Neutron radiography was simultaneously implemented to create images of the internal working fluid flow at a rate of 30 frames per second. Results show the average temperature drop from the evaporator to condenser decreases at higher heat inputs due to an increase in temperature throughout the condenser region due to greater oscillations. These large oscillations were visually observed using neutron radiography. As the operating temperature is increased, the thermal resistance is reduced. A decrease in filling ratio tends to create more steady fluid motion; however, the heat transfer performance is reduced.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

20-turn (a and b) and 10-turn (c) OHPs

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Figure 2

Dimensions and thermocouple locations for the 20-turn (a) and 10-turn (b) OHPs (dimensions in mm)

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Figure 3

Experimental setup

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Figure 4

Neutron imaging setup

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Figure 5

Temperature data for the startup stage for the 20-turn OHP

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Figure 6

Temperature data for the intermittent stage for the 20-turn OHP (heat input: 50 W, condenser setting: 60°C)

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Figure 7

Neutron images of the intermittent stage for the 20-turn OHP at (a) 70 s, (b) 75 s, (c) 80 s, and (d) 85 s

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Figure 8

Temperature data for the bulk circulation stage for the 20-turn OHP (heat input: 300 W, condenser setting: 60°C)

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Figure 9

Neutron images of the circulation stage for the 20-turn OHP at (a) 6.1 s, (b) 8.0 s, (c) 9.9 s, and (d) 11.6 s

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Figure 10

Temperature drop versus heat flux for the 20-turn OHP

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Figure 11

Thermal resistance versus heat flux for the 20-turn OHP

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Figure 12

Startup of the 10-turn OHP at (a) 0 s, (b) 400 s, and (c) 600 s

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Figure 13

Temperature fluctuations at a filling ratio of 53% for the 10-turn OHP

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Figure 14

Temperature fluctuations at filling ratio of 35% for the 10-turn OHP

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Figure 15

Temperature fluctuations at a filling ratio of 30% for the 10-turn OHP

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Figure 16

Typical fluid distribution at low heat input for filling ratio of (a) 53%, (b) 35%, and (c) 30%

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Figure 17

Temperature drop given different filling ratios for the 10-turn OHP

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Figure 18

Thermal resistance given different filling ratios for the 10-turn OHP

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