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Thermocapillary Phenomena and Performance Limitations of a Wickless Heat Pipe in Microgravity

Akshay Kundan, Joel L. Plawsky, Peter C. Wayner, Jr., David F. Chao, Ronald J. Sicker, Brian J. Motil, Tibor Lorik, Louis Chestney, John Eustace, and John Zoldak
Phys. Rev. Lett. 114, 146105 – Published 7 April 2015
Physics logo See Synopsis: Staying Cool in Outer Space
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Abstract

A counterintuitive, thermocapillary-induced limit to heat- pipe performance was observed that is not predicted by current thermal-fluid models. Heat pipes operate under a number of physical constraints including the capillary, boiling, sonic, and entrainment limits that fundamentally affect their performance. Temperature gradients near the heated end may be high enough to generate significant Marangoni forces that oppose the return flow of liquid from the cold end. These forces are believed to exacerbate dry out conditions and force the capillary limit to be reached prematurely. Using a combination of image and thermal data from experiments conducted on the International Space Station with a transparent heat pipe, we show that in the presence of significant Marangoni forces, dry out is not the initial mechanism limiting performance, but that the physical cause is exactly the opposite behavior: flooding of the hot end with liquid. The observed effect is a consequence of the competition between capillary and Marangoni-induced forces. The temperature signature of flooding is virtually identical to dry out, making diagnosis difficult without direct visual observation of the vapor-liquid interface.

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  • Received 9 December 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.146105

© 2015 American Physical Society

Synopsis

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Staying Cool in Outer Space

Published 7 April 2015

In the absence of gravity, surface tension forces affect how fluids flow in heat pipes and may limit the device’s cooling performance on spacecraft missions.

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Authors & Affiliations

Akshay Kundan1, Joel L. Plawsky1,*, Peter C. Wayner, Jr.1, David F. Chao2, Ronald J. Sicker2, Brian J. Motil2, Tibor Lorik3, Louis Chestney3, John Eustace3, and John Zoldak3

  • 1The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
  • 2NASA Glenn Research Center, Cleveland, Ohio 44135, USA
  • 3Zin Technologies, Cleveland, Ohio 44130, USA

  • *Corresponding author. plawsky@rpi.edu

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Issue

Vol. 114, Iss. 14 — 10 April 2015

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