• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.8
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• pp.1038-1045
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• 2000

An experimental study was carried out to delineate the flow characteristics in a closed countescurrent two-phase thermo syphon with concentric tubes. This is to be installed in the HANARO research reactor as a part of a Cold Neutron Source(CNS). In the present investigation, experiments ata room temperature with Freon-II3 as a moderator were performed. Results show that, based on the magnitude of pressure fluctuation, the flow regimes could be divided into 4 distinct ones in the ($V_f,\;Q_i$) plane, where $V_f$ represents the volume of the charged liquid and $Q_i$ the heat load: a stable flow regime, an oscillatory flow regime, a restablized flow regime and a dryout flow regime. For $V_f$>2.5l, the flow is stable at low $Q_i$. However, as $Q_i$ increases, the flow becomes oscillatory and finally restablizes As $V_f$ increases, the oscillation amplitude decreases, reaching to the restablized flow region at low $Q_i$, and the liquid level in the moderator cell remains high. In the oscillatory flow regimes, for a fixed VI; the oscillating period of time varies with $Q_i$, having a minimum value at a certain value of $Q_i$. The heat load, where the oscillating period of time is minimum, decreases as $V_f$ increases.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.238-245
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• 1999

For the optimal design of plasma facing components of a fusion reactor, thorough understanding of thermal behavior of high heat. nux components are required. The purpose of this research is to investigate the characteristics of heat flow and thermal stress in divertors which are exposed to high heat load varing with time and space-Numerical simulations of heat now and thermal stress for three types of diverter are performed using finite volume method and finite element method. Respectly, commercial FLUENT code are used in the heat flow simulation, and maximum surface temperature, temperature distribution and cooling rate are calculated. Commercial ABQUS code are used for calculating temperature distribution. thermal stress, strain and displacement. Through this computer simulation. design data for cooling system and Structural provided.