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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Flow Visualisation in a Transparent Thermosyphon: Influence of Internal Pressure

Kate Smith
Department of Mechanical & Manufacturing Engineering, Trinity College

Roger Kempers
York University

Anthony J. Robinson
Department of Mechanical and Manufacturing Engineering, Parsons Building, Trinity College, Dublin, Ireland; and Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada

Samuel Siedel
Department of Mechanical & Manufacturing Engineering, Trinity College

DOI: 10.1615/IHTC15.hpp.008985
pages 3743-3750


KEY WORDS: Heat pipe, Two-phase/Multiphase flow, Transparent test section, fluid mechanics

Abstract

Heat pipes and thermosyphons are generally recognized as a reliable heat transfer device for many different applications however clarity is needed to describe the thermal mechanisms driving the transfer of heat. This experiment involved the construction and testing of a transparent, sapphire thermosyphon, with water as the working fluid. Through high speed imagery and corresponding temperature and pressure measurements, the dominant mechanisms of boiling and condensation were visualized in the evaporator and condenser. The tests were carried out at various internal pressures, which ranged from P = 4 - 25 kPa, at a constant heat input of Q = 50 W. Of particular interest was the pulsating nature of the thermosyphon at lower pressure levels. The high speed images show, at lower pressures, a liquid plug and vapor slug were seen to oscillate between the evaporator and condenser. At the higher pressures tested, film condensation becomes more dominant in the condenser and the frequency and amplitude of liquid oscillations is reduced. The overall thermal resistance of the system was also calculated, and ranged from Rtot = 0.44 K/W at low pressure, to Rtot = 0.10 K/W at higher pressure.

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