| Summary: | 碩士 === 國立高雄海洋科技大學 === 輪機工程研究所 === 102 === As an attempt to reduce the degradation of the thermal performance for a
Two Phase Loop Thermosyphon (TPLT) operated at vacuum pressures
due to the effects of boiling instabilities, this experimental study proposed
the scale-roughened evaporator to increase nucleate sites, reduce bubble
waiting time and moderate the pressure waves transmitted from bubble
eruptions for reducing the interface oscillations so that the overall thermal
performances of the TPLT can be improved. With the heater power of
evaporator (Q) and the condenser thermal resistance (Rth,con) as the
controlling parameters, the thermodynamic cycles, thermal networks,
boiling instabilities for two TPLTs with smooth and scale-roughened
evaporators are comparatively analyzed. The variations of the saturated
pressures against boiling number (Bo) and Rth,con in each evaporator of the
two TPLTs are also examined. The tested Q and Rth,con are in the
respective ranges of 90-210W and 0.25-0.45 KW-1. With the
scale-roughened evaporator, the thermal resistances caused by the
pre-heating effects as a result of the boiling instabilities are considerably
reduce due to the weakened pressure wave oscillations, the reduced
bubble waiting time and the extension of nucleate boiling regime. With
the reduced boiling instabilities, the cooling power consumptions over the
condenser for the scale-roughened TPLT are considerably reduced to
1/1.5~1/2.5 times of those required for the smooth-walled TPLT. The
empirical correlations for evaluating the boiling heat transfer rates,
saturated pressures of evaporator and the total thermal resistance of
present scale-roughened TPLT are generated as the design references for
the relevant industries.
Keywords: Two Phase Loop Thermosyphon, Scale-roughened Evaporator,
Boiling instabilitiy.
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