Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

A. Vadnjal
University of California at Los Angeles, Los Angeles, United States

Ivan Catton
Morin, Martinelli, Gier Memorial Heat Transfer Laboratory, Department of Mechanical and Aerospace Engineering, School of Engineering and Applied Science, University of California, Los Angeles, USA

The heat transfer model of a bi-porous wick developed in this work is characterized by three stages; conduction, large pore dryout and small pore dryout. These stages are bounded by two characteristic limits; the nucleation and the capillary limits. The operating limit of the wick must have a safe margin below complete dry out. Complete dry out of the wick leads to an uncontrolled excursion of the wall temperature, therefore more effort has been devoted to modelling the small pore dry out limit. In this limit, three physical processes govern heat removal. These are characterized the driving and resisting forces in the bi-porous wick. The driving force for liquid distribution within the wick is capillary force created by the small pores. The resistance to flow is a result of liquid flow in the small pores and vapour flow in the large pores. Current emphasis in the modelling is on the two limits and the initial conduction region. The current model agrees with measurements for various configurations of thin bi-porous wicks tested with different working fluids. By varying wick geometry, especially the large and small pores, an improvement in heat flux magnitude is achieved as a result of the capillary pumping power and the vapor escape passages.

PRT-17 pages DOI: 10.1615/IHTC13.p5.170 Download article

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