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Heat Pipe Science and Technology, An International Journal

Publication de 4  numéros par an

ISSN Imprimer: 2151-7975

ISSN En ligne: 2151-7991

VISUALIZATION OF OSCILLATING HEAT PIPE UNDER MICROGRAVITY

Volume 5, Numéro 1-4, 2014, pp. 425-431
DOI: 10.1615/HeatPipeScieTech.v5.i1-4.480
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RÉSUMÉ

Visualization experiments on oscillating heat pipes (OHPs) are conducted under high gravity and microgravity to understand the physical phenomena of OHPs under both environments. An OHP connected to a liquid reservoir operates as a variable-conductance OHP (VC-OHP), and both OHPs and VC-OHPs are used in the experiments An OHP consists of a Pyrex glass capillary tube (inner diameter: 1.5 mm; outer diameter: 8 mm) that meanders between a heating section and a cooling section 5 times in each direction (10 times in total). A 50-mL reservoir is connected to an OHP via another capillary tube. There is a valve between this reservoir and the OHP. The valve is closed in the simulation of the fixed-conductance OHP (FC-OHP). 1,1,1,2- Tetrafluoroethane (HFC-134a) is used as the working fluid. The reservoir temperature is kept at 35 °C by the heater. A silicon rubber heater is twisted around one part of the glass OHP. Glass OHPs with and without liquid reservoirs are mounted on an MU-300 jet for the microgravity experiment. A parabolic pattern flight by the jet provides an approximately 20 s microgravity condition (less than 0.01 g). A hypergravity condition extends about 30 s before and 30 s after the microgravity condition. The parabolic flight was repeated 11 times in a 1 h flight. A video of the OHP was taken during the experiments. There is little difference between the operation of the VC-OHP and FC-OHP under hypergravity just before the microgravity condition. The vapor plugs and liquid slugs in the VC-OHP flow in one direction under the microgravity condition while the flow in the FCOHP almost stops and only intermittently oscillating flow of a few vapor plugs is caused.

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