Experimental Study on Vibration Suppression Control of Flexible Structures with Flexible Space Robotic Arm Operation
- Paper number
IAC-05-C1.4.09
- Author
Mr. Kazuya Konoue, Tokyo Institute of Technology, Japan
- Coauthor
Mr. Masashi Asami, Tokyo Institute of Technology, Japan
- Coauthor
Prof. Saburo Matunaga, Tokyo Institute of Technology, Japan
- Year
2005
- Abstract
Boiling crisis is a transition from a regime, where vapor bubbles nucleate separately on the heater wall, to a regime where the heater wall is entirely covered by a continuous vapor film. When formed, the vapor film reduces drastically the heat transfer at the heater wall, due to the gas thermal transport properties lower than the liquid ones. Obviously, the boiling crisis occurs when the heat flux exceeds a threshold value, called the critical heat flux, which estimation is essential in the industrial heat exchanger design and management. We have proposed to investigate the triggering mechanism at the origin of the boiling crisis by direct observation of a gas bubble spread over a heater surface, during the heating of a critical two-phase fluid (SF6), using the CNES-NASA DECLIC facility on board the International Space Station. The microgravity conditions which cancel buoyancy forces and generate three-dimensional spherical shape of the gas bubble is an irreplaceable powerful tool for studying the boiling crisis. The main originalities of these investigations are provided by monitoring of low heat fluxes and fine control of the liquid-vapor properties, by adjustment of the distance to the critical point, taking advantage of the simplifications due to the low temperature gradients and the universal description of critical phenomena. A new pressurized optical cell integrates an in-situ heating device as a form of transparent resistive layer ( 50 mm2 area) appropriate for light transmission observation of the liquid film boiling. High-resolution (1000x1000 pixels) and high-speed (462 fr/s) optical diagnoses are synchronized with in situ temperature measurements, and adjusted to the selected monitoring rate of the thermal stimuli produced by the transparent resistive heater. The ALI-DECLIC insert allows injecting a thermal power covering the range 0 - 3.4 mW and simultaneously acquires at high frequency (2 kHz) data from 3 thermistors (THERMOMETRICS B10) located inside the fluid. The heat power per unit area can then be controlled in the range 0.75 mW/m2 to 75 W/m2. Heating period can be adjusted (with a minimum of 42 ms). Resolution from the B10 sensors is better than 0.02 Ω, corresponding to temperature accuracy around 0.1mK. Illustrations of the high-level performances are provided by the results obtained during the Earth’s tests of the flight model of the ALI insert using the observation of the Rayleigh-Benard convective cells near the liquid-vapor critical point of SF6, when generated by heating the fluid through the transparent resistive layer.
- Abstract document
- Manuscript document
IAC-05-C1.4.09.pdf (🔒 authorized access only).
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