Annals of the Assembly for International Heat Transfer Conference 13

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

Year 2006

Tadej Semenic
Morrin-Martinelli-Gier Memorial Heat Transfer Laboratory, Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, Box 951597, CA 90095-1597

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

A biporous medium is a porous medium that has two level characteristic capillary pore radii. In present work, the biporous medium is made with sintering together clusters of spherical copper powder into a layer of uniform thickness and used as an evaporating surface. During the operation of the biporous wick, clusters are in a capillary contact and pump working fluid to evaporating menisci located on the surface of the clusters, while pores between clusters act as vapor channels to remove the vapor from the wick. The biporous wicks are very attractive candidates for high heat flux applications. For an optimal operation of a biporous wick geometrical parameters of the wick, such as powder size, cluster size, wick thickness, and liquid feed length need to be optimized in terms of capillarity and liquid permeability of small pores between the powder, vapor permeability of large pores between the clusters, and effective thermal conductivity of the wick, in a way to remove maximum heat flux at a minimum superheat. In this work, thirteen biporous wicks with cluster average diameters 302, 605, 855, and 1015 μm and powder particle average diameters 38, 58, and 76 μm and one wick made of porous particles with inner pore size unknown were sintered into wicks of uniform thickness. Wicks were tested with degassed distilled water at 0.07 bar vapor pressure. The best performed biporous wick with cluster/powder/thickness [μm] 605/38/2000 removing 332.1 W/cm² at effective heat transfer coefficient 5.3 W/cm²K and interface wick/wall temperature 104.5 °C.

PRT-18 pages DOI: 10.1615/IHTC13.p5.180 Download article

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