水平和竖直细圆管内流动凝结换热特性的对比研究

THE STUDY ON CONDENSATION HEAT TRANSFERCHARACTERISTICS FOR VAPOR FLOWIN HORIZONTAL AND VERTICALSMALL DIAMETER TUBES

本文采用基于相平衡理论的最小能量原理，根据当地气液两相流动条件确定气液界面形状，以此为基础，从理论上探讨水平细圆管内流动凝结的特点。通过与竖直条件下管内凝结换热特性的对比，分析重力、气液界面剪切力、表面张力对流动凝结的影响。研究发现，细圆管由竖直变为水平放置时，管径的减小同样导致重力的影响削弱，并且凝结换热得到进一步强化；但由于流型的变化，随管径的减小强化的程度减弱。

Employing the minimum energy principle to determine the vapor-liquid interfaceconfiguration, this paper established an analytical model to explore the heat transfer Characteristics of flow condensation in horizontal small/mini diameter tube. Compared with thatin vertical tube, the effects of shear stress, surface tension and gravity on flow condensationare analyzed. The results indicate that, both in vertical and horizontal tube, decreasing thetube diameter leads to the gravity effect weakening, and as the tube is located from verticalto horizontal, condensation is enhanced. However, in small diameter tube, because of vaporliquid interface curvature increasing, the heat transfer enhancement isn't as obvious as thatin large diameter tube.