热力学
热流密度
传热系数
材料科学
鳍
传热
制冷剂
蒸发
压力降
质量通量
管(容器)
机械
二氧化碳
传质
化学
复合材料
热交换器
物理
有机化学
作者
Jin Min Cho,Min Soo Kim
标识
DOI:10.1016/j.ijrefrig.2007.01.007
摘要
Carbon dioxide among natural refrigerants has gained a considerable attention as an alternative refrigerant due to its excellent thermophysical properties. In-tube evaporation heat transfer characteristics of carbon dioxide were experimentally investigated and analyzed as a function of evaporating temperature, mass flux, heat flux and tube geometry. Heat transfer coefficient data during evaporation process of carbon dioxide were measured for 5 m long smooth and micro-fin tubes with outer diameters of 5 and 9.52 mm. The tests were conducted at mass fluxes of from 212 to 656 kg m−2 s−1, saturation temperatures of from 0 to 20 °C and heat fluxes of from 6 to 20 kW m−2. The difference of heat transfer characteristics between smooth and micro-fin tubes and the effect of mass flux, heat flux, and evaporation temperature on enhancement factor (EF) and penalty factor (PF) were presented. Average evaporation heat transfer coefficients for a micro-fin tube were approximately 150–200% for 9.52 mm OD tube and 170–210% for 5 mm OD tube higher than those for the smooth tube at the same test conditions. The effect of pressure drop expressed by measured penalty factor of 1.2–1.35 was smaller than that of heat transfer enhancement.
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