The Effects of Transverse Acceleration-Induced Body Forces on the Capillary Limit of Helically Grooved Heat Pipes

Abstract

A helically grooved copper heat pipe with ethanol as the working fluid has been fabricated and tested on a centrifuge table. The heat pipe was bent to match the radius of curvature of the table so that uniform transverse (perpendicular to the axis of the heat pipe) body force fields could be applied along the entire length of the pipe. By varying the heat input (Qin = 25 to 250 W) and centrifuge table velocity (radial acceleration |a⃗r| = 0 to 10g), information on dry out phenomena, circumferential temperature uniformity, heat lost to the environment, thermal resistance, and the capillary limit to heat transport was obtained. Due to the geometry of the helical grooves, the capillary limit increased by a factor of five when the radial acceleration increased from |a⃗r| = 0 to 6.0g. This important result was verified by a mathematical model of the heat pipe system, wherein the capillary limit to heat transport of each groove was calculated in terms of centrifuge table angular velocity, the geometry of the heat pipe and the grooves (including helix pitch), and temperature-dependent working fluid properties. In addition, a qualitative study was executed with a copper-ethanol heat pipe with straight axial grooves. This experimental study showed that the performance of the heat pipe with straight grooves was not improved when the radial acceleration was increased from |a⃗r| = 0 to 10.0g.

Thermal design of a disk‐array system

“…Sheihk and Garimella, 2000;Kodo et al, 2000;Culham and Muzychka, 2001) using conventional convective heat transfer principles may not be enough. Devices using phase-change principles have attracted lots of notice (Peterson, 1992;Peterson, 1996;Ha and Peterson, 1998;Thomas et al, 1998;Namba et al, 1999;Zuo et al, 2001). Board-level heat transfer problems have been studied by many investigators (Sparrow et al, 1982;Davalath and Bayazitoglu, 1987;Rajakumar and Johnson, 1989;Agonafer and Moffatt, 1990;Amon, 1992;Asako and Faghri, 1994;Wirtz and Mathur, 1994).…”

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“…Thomas et al [8] examined the behavior of a helically grooved copper-ethanol heat pipe in terms of the evaporator heat input and transverse radial acceleration. Heat loads ranging from Q in 20 to 250 W were applied to the evaporator.…”

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“…Helically grooved copper heat pipes with ethanol as the working fluid were tested under centrifugal motion by Thomas et al [46] in order to study the effects on the capillary limit of body forces induced by transverse acceleration. Information on the dry out, circumferential temperature uniformity, heat loss to the environment, thermal resistance and capillary limit was obtained.…”