Publication de 4 numéros par an
ISSN Imprimer: 2151-7975
ISSN En ligne: 2151-7991
VISUALIZATION OF OSCILLATING HEAT PIPE UNDER MICROGRAVITY
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.