Thermal Behavior of Axially Grooved Heat Pipes aboard a Rocket

概要

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Two axially grooved heat pipes, one using ammonia as the working fluid and another using freon 11,were launched aboard S-520 sounding rockets in January 1980 and in September 1981,respectively. The former was made of aluminum and the latter of aluminum alloy. N-eicosane was employed as a phase change heat sink material for both cases. They were fixed on the rocket axis with the condenser top. The heat pipes experienced several levels of varying acceleration such as large positive during the boosting period, small negative immediately after the burnout caused by the aerodynamic drag on the rocket, zero-gravity, and again positive while the re-entry. They responded to these situations. Such responses as dryout, recovery from the dryout with partial liquid blockage in the condenser section, and resumption of normal heat pipe operation were resulted from the dynamic behavior of the working fluid. The flight data were analyzed to understand the heat pipe performance and to investigate the dependence of the liquid motion on the body force and on the surface tension. The critical Bond number which gave a boundary between surface tension dominating and body force dominating regions was found to be the order of 10^-3
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