An experimental study of thermal performance for a two phase loop thermosyphon with scale-roughened boiling surface at vacuum pressure

• Main Authors: LIN, CHING-YUAN, 林敬原
• Other Authors: Chang, Shyy Woei
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/87333961989154696704

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.