蒸气在倾斜细小直径圆管内的流动凝结换热特性

细小管内的流动凝结换热具有许多超常换热特性,经典的Ｎｕｓｓｅｌｔ分析方法已不能满足需要。在以往研究的基础上,本文进一步通过实验探析换热温差和蒸气流量对不同直径的细小管内流动凝结换热的影响。研究表明,管径越小,换热温差对凝结换热系数的影响程度越低;通过流量和倾角对凝结换热数的影响,分析了重力引发的流动分层和剪切力对凝结液的排除两种因素对细管传热强化的作用机制。本文的实验结果和用于常规尺度下的通用关联式对比表明,采用细管,管内的流动凝结换热得到无可置疑的强化

CONDENSATION HEAT TRANSFER CHARACTERISTICS FOR VAPOR FLOW INSIDE ALONG SMALL/MINI-DIAMETER TUBES

There are many peculiar characteristics of flow condensation heat transfer in small/mini- diameter tube, for which the classical Nusselt theory cannot be well applied. Based on our previous studies, this paper explores effects of temperature difference and mass flux on flow condensation in small/mini-diameter tube by experimental study. The results indicate that, as reducing tube diameter, temperature difference has decreasing effect on heat transfer coefficiefit. Heat transfer enhancement due to fluids stratification by gravity and condensate remove by shear stress are also investigated by influences of mass flux and test tube inclination angle on heat transfer coefficient. Comparison of the experimental data with prediction of the existing correlation for larger signed commercial tubes implies an obvious condensation heat transfer enhancement by small/mini-diameter tube