倾斜特长异型管内单组分蒸汽强迫对流凝结特性研究

Air-cooled condenser is used in many thermal power plants, it has been proved that air-cooled technology has a very significant water-saving effect. During the operation of air-cooled condenser unit, there are many factors, such as steam condensation in tube, the change of flow resistance in tube, ambient air condition, the structure of finned tube etc., which will influence the heat transfer ability of air-cooled condenser, and result in the increase of exhaust steam pressure, decrease of the ability of power output. To enhance the heat transfer performance, it is necessary to conduct a thorough study of the flow and heat transfer phenomena within and outside of the tube. As the performance of condensation heat exchanger of air-cooled island plays a decisive role in energy-saving, in order to reduce the flow resistance of the air side, finned oval tube heat exchanger is commonly used in condensation heat exchanger of air-cooled island. Extremely long inclined elliptic tube is used , in which vapor is condensed by forced convection inside the tube. Considering the facts that there are less studies of single component vapor condensation performances in extremely long inclined elliptic tube and single component vapor condensation characteristics obtained in inclined circle tube are not suitable for predicting the characteristics in inclined elliptic tube, it is very necessary to conduct the studies of single component vapor forced convective condensation performances in extremely long elliptic tube. This project tries to inverstigate following four aspects usin experimental method:(1)obtaining single component vapor forced convective condensation performance in inclined elliptical tube;（2)comparing the differences of single component vapor forced convective condensation performances between inclined elliptic tube heat exchanger and inclined circle tube, and analyzing the mechanics of resulting in the differences;（3)analyzing the effect and its degree of tube geometry, working condition, angle of inclination and the tube length on the mechanism of single component vapor forced convective condensation characteristics in inclined elliptical tube;（4)obtaining the similar conditions for single component forced convective condensation properties. The goal of the project is to get the single component vapor forced convective condensation characteristics in extremely long and inclined oval tube. The findings of the project are not only to promote the understanding and description of the single component vapor forced convective condensation characteristics in extremely long inclined oval tube, but also to acquire the basis data for design of extremely long inclined oval tube heat exchanger.

为了减少水资源消耗，直接空冷电站使用倾斜特长(l/de≈350)异型管换热器。蒸汽在其管内做单组分蒸汽强迫对流凝结。该凝结特性影响着电站的节能减排水平。在对已获得的倾斜圆管内单组分强迫对流凝结特性无法用于预测倾斜异型管内单组分蒸汽强迫对流凝结特性的背景下，非常有必要对倾斜特长异型管内单组分蒸汽强迫对流凝结特性进行研究。项目用实验的方法拟开展四方面的研究：1.倾斜异形管内单组分强迫对流凝结特性；2.比较倾斜异形管与圆管管内单组分强迫对流凝结特性的不同及引起其不同的机理；3.管子几何形状、工况、倾角及管长组对倾斜异形管内单组分强迫对流凝结特性的影响程度及机理；4.倾斜异形管内单组分强迫对流凝结特性的相似条件。目标是获得倾斜特长异形管内单组分蒸汽强迫对流凝结特性。项目的研究结果不仅可增进倾斜异形管内单组分蒸汽强迫对流凝结现象的认识和描述，还将是设计倾斜特长异型管管内凝结换热器的基础数据。

倾斜特长管内的蒸汽凝结在理论上一直是比较难以准确定量，其总的换热系数受管内蒸汽的换热系数、管外空气侧换热系数和管的导热系数的影响，因此为获得管内蒸汽凝结的换热规律，项目搭建了蒸汽强迫对流凝结实验装置，分别测试了倾斜特长扁管结构实验试件管内凝结传热特性的基础数据、倾斜特长圆管肋侧传热特性的基础数据，对倾斜特长异型管外两种翅片传热特性进行了数值分析，并且在实验室采用激光干涉法完成了管横截面上液膜厚度的测量。通过项目的执行，对倾斜特长管内的蒸汽凝结的换热特性有了新的认识。研究发现扁管结构实验试件在相同冷却风流量下，换热量与管内压降随着散热器倾斜角度的增加而增加。且在倾斜角度为90°时压降达到最大；在不同倾斜角度下，随着入口蒸汽质量流量的增加管内凝结换热系数逐渐增大，不同倾斜角度保持相同的冷凝水Rel数，管内凝结换热系数区别不大。.对于带凹坑翅片，凹坑能够提高扁管与带凹坑翅片形成的通道内的二次流强度。二次流强度Sem、努塞尔数Num和阻力系数f与Re和凹坑结构各参数有着紧密的联系。翅片表面的凹坑不但能够影响翅片上下表面的Nus，而且还能影响管壁和翅片侧面的Nus。.对于间断波纹连续翅片，在同一翅片间距、波形间距、波形高度条件下，翅侧通道的平均努塞尔数随着雷诺数的增大而增大，对流换热的阻力系数随着雷诺数的增大而减少，纵向涡强度随着雷诺数的增大而增大，横向涡的强度随着雷诺数的增大而增大。同样的雷诺数下，翅侧通道的平均努塞尔数随着翅片波形高度增大而增大，阻力系数也随着波形高度增大而增大，纵向涡强度随着波形高度增大而增大，横向涡强度随着波形高度增大而减小。纵向涡强度随着翅片间距增大而增大，横向涡强度也随着翅片间距的增大而增大。.另外，项目采用激光干涉法在实验室测量了管横截面上液膜厚度。.项目结果可增进对倾斜特长异型管管内蒸汽凝结现象的认识，指导降低空冷岛能耗的设计，具有较大的学术意义和较高的工程应用价值。研究成果已在国内外发表标注期刊论文和会议论文6篇，已被SCI收录3篇，EI收录2篇；授权发明专利21项；项目培养研究生4名。