Heat Transfrer Characteristics of Dropwise Condensation of Steam on a Vertical Bank of Horizontal Circular Tubes

本研究的目的是验证我们的预测，在滴状冷凝的情况下，传热性能不会恶化到一定数量的行，在一个垂直银行的水平管。由于淹没的影响，气膜冷凝的换热系数随着排数的增加而减小。然而，在滴状冷凝的情况下，从上级管落下的液滴频繁地扫掠表面可能会增强传热，并且会超过淹没的效果。对水蒸气在水平管外表面的膜状冷凝和滴状冷凝进行了传热实验研究。通过调节从其上放置的穿孔管向试管中排水的流量来模拟冷凝水从管束中滴落的效果，得到的结论是：“（1）如果设计和制造得当，用滴水管可以很好地模拟管束。(2)在本实验条件下，蒸汽在管束上滴状冷凝的传热系数在第10级左右没有恶化。

An objective of this study was to verify our prediction that, in the case of dropwise condensation, the heat transfer performance would not be deteriorated up to a certain number of rows, in a vertical bank of horizontal tubes. The heat transfer coefficient of film condensation decreases as the number of rows increases due to the effect of inundation. However, frequent sweing of the surface by drops falling from superior tubes are likely to enhance the heat transfer in the case of dropwise condensation, and would exceed the effect of inundation. Heat transfer measurements were carried out for both film and dropwise condensation of steam on the outside surface of a horizontal tube. The effect of the condensate dropping from the bank of tubes was simulated by regulating the flow rate of water draining onto the test tube from a perforated thbe placed just above.Conclusions obtained were:"(1) A bank of tube could be well simulated using a dripping tube, if it was designed and manufactured properly.(2) Heat transfer coefficient of dropwise condensation of steam on a bank of tubes did not deteriorate up to about tenth stage under the experimental condition employed in the present study.