两相闭式热虹吸管冷凝换热规律的实验研究

EXPERIMENTAL INVESTIGATION OF CONDENSATION HEAT TRANSFER PROCEDURE OF TWO-PHASE CLOSED THERMOSYPHON

本文通过可视化热虹吸管实验,拍摄了冷凝段内部冷凝液的各种基本流型和特殊流型,设计了试验用多节风冷热虹吸管以及相应的风道系统。采用自行组装的高精度微机控制的测试系统测量温度,对不同工质(水、乙醇、丙酮、氟里昂-11)热虹吸管进行了不同工况的实验。获得了各种工程实际工况下的冷凝换热系数,还获得了冷凝换热系数随热流密度、蒸汽压力变化的规律以及沿2.5米长冷凝面长度上的变化规律。实验结果表明,热虹吸管的冷凝换热系数在很大范围内偏离努塞尔特理论解。本文结合可视化实验,对其进行了分析。

Various kinds of basic condensate flow patterns at the condenser section of the two-phase closed thermosyphon were photoed by using a transparent thermosyphon. The experimental carbon-steel thermosyphon with several air cooling sections was designed and an air cooling system was set up. The temperature was measured using an automatic measuring system, which was of high accuracy and controlled by an Apple-Ⅱ computer. Several working fluids(water, ethanol, acetone, freon-11)were tested under different operating conditions. The condensation heat transfer coefficients were obtained under practical operating conditions in industries. According to the experimental results, there existed a wide difference between Nusselt's results and our results, which was explained based on the results of visual study.