Experimental study on the evaporative heat transfer and pressure drop of CO2 flowing upward in vertical smooth and micro-fin tubes with the diameter of 5 mm
Experimental study on the evaporative heat transfer and pressure drop of CO2 flowing upward in vertical smooth and micro-fin tubes with the diameter of 5 mm
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DOI：
10.1016/j.ijrefrig.2007.12.001
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发表时间：
2008-08
期刊：
影响因子：
--
通讯作者：
Y. J. Kim;J. Cho;M. S. Kim
中科院分区：
文献类型：
--
作者：
Y. J. Kim;J. Cho;M. S. Kim
由于臭氧层破坏和全球变暖，正在开发新的替代制冷剂。通过实验研究了CO2在垂直光管和微肋管内上升流动时的蒸发传热特性和压降，并对蒸发温度、质量流量和热流密度进行了分析。选用外径为5 mm、长度为1.44m的竖直光管和微肋管作为实验段，测量其蒸发换热系数。试验在质量通量为212至530 kg/（m2 s）、饱和温度为−5至20°C和热通量为15至45 kW/m2的条件下进行，其中试验段通过直接加热法加热。从强化因子（EF）和惩罚因子（PF）两个方面分析了光滑管和微肋管的传热特性差异。在相同的试验条件下，微肋管的平均蒸发换热系数比光管高111-207%，PF值从106%提高到123%。
Because of the ozone layer depletion and global warming, new alternative refrigerants are being developed. In this study, evaporation heat transfer characteristic and pressure drop of carbon dioxide flowing upward in vertical smooth and micro-fin tubes were investigated by experiment with regard to evaporating temperature, mass flux and heat flux. The vertical smooth and micro-fin tubes with outer diameter (OD) of 5mm and length of 1.44m were selected as a test section to measure the evaporative heat transfer coefficient. The tests were conducted at mass fluxes from 212 to 530kg/(m2s), saturation temperatures from −5 to 20°C and heat fluxes from 15 to 45kW/m2, where the test section was heated by a direct heating method. The differences of heat transfer characteristics between the smooth and the micro-fin tubes were analyzed with respect to enhancement factor (EF) and penalty factor (PF). Average evaporation heat transfer coefficients for the micro-fin tube were approximately 111–207% higher than those for the smooth tube at the same test conditions, and PF was increased from 106 to 123%.