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Technical Briefs

The Effect of Fill Volume on Heat Transfer From Air-Cooled Thermosyphons

[+] Author and Article Information
Christina A. Pappas

Graduate Student
Department of Mechanical and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VA 22904
e-mail: caj5p@virginia.edu

Paul M. De Cecchis

Major U.S. Army
Aviation Applied Technical Directorate,
Fort Eustis, VA 23604
e-mail: pauldececchis@us.army.mil

Donald A. Jordan

Senior Research Scientist
e-mail: dj8n@virginia.edu

Pamela M. Norris

Professor
Fellow ASME
e-mail: pamela@virginia.edu
Department of Mechanical and Aerospace Engineering,
University of Virginia,
122 Engineer's Way,
Charlottesville, VA 22904

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received March 26, 2012; final manuscript received November 19, 2012; published online March 20, 2013. Assoc. Editor: Bruce L. Drolen.

J. Heat Transfer 135(4), 044504 (Mar 20, 2013) (4 pages) Paper No: HT-12-1133; doi: 10.1115/1.4023039 History: Received March 26, 2012; Revised November 19, 2012

The effect of fill volume on the heat transfer performance of a cylindrical thermosyphon with an aspect ratio (ratio of the length of the evaporator section to the inner diameter) of 2.33 immersed in a cooling air flow is investigated. The fill volume was systematically varied from 0% to 70.3% of the volume of the evaporator section in a copper-water thermosyphon having an inner diameter of 19 mm. The condenser section was immersed in a uniform air flow in the test section of an open return wind tunnel. The heat transfer rate was measured as a function of evaporator temperature and fill volume, and these results were characterized by three distinct regions. From 0% to roughly 16% fill volume (Region I), the low rate of heat transfer, which is insensitive to fill volume, suggests that dry out may be occurring. In Region II (extending to approximately 58% fill volume), the heat transfer rate increases approximately linearly with fill volume, and increasing evaporator temperature results in decreased rate of heat transfer. Finally, in Region III (from roughly 58–70.3%), the rate of heat transfer increases more rapidly, though still linearly, with fill volume, and increasing evaporator temperature results in increased rate of heat transfer. The thermosyphon rate of heat transfer is greatest at 70.3% fill volume for every evaporator temperature.

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References

Figures

Grahic Jump Location
Fig. 1

An illustration of the steady state nature of the experiment where the rate of heat transfer to the airstream, Q·out, is equivalent to the power input to the electrical cartridge heaters, Q·in

Grahic Jump Location
Fig. 2

An illustration of the thermosyphon and heater block used in these experiments, including the locations of the five thermocouples placed along the length of the condenser section (spaced equally apart at distance of 50.8 mm)

Grahic Jump Location
Fig. 3

A diagram illustrating the configuration of the vacuum system, fluid reservoir, and the thermosyphon

Grahic Jump Location
Fig. 4

The rate of heat transfer for four evaporator temperatures at various fill volumes and the predicted rate of heat transfer for the 149 °C evaporator temperature (an example error bar for the Zhukauskas correlation is provided at 70.3% fill volume for the 149 °C evaporator temperature)

Grahic Jump Location
Fig. 5

The surface temperature distribution along the length of the thermosyphon for selected fill volumes in each region at the 149 °C evaporator temperature

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