基于CFD数值模拟的换热器外导流筒结构选型

摘要

The uniform distribution of flow field in the shell-side of the shell-and-tube heat exchanger could improve the heat transfer effect.The rational selection of the external flow distributor has important influence on the uniformity of the flow field.However,the external flow distributor has various structures,and its design is more dependent on experience and lack of guidance method.In view of this,three-dimensional solid models with three kinds of structures have been established,and the external flow distributor has been designed for the heat exchange section of the vertical tube falling-film evaporator with a cylinder diameter of 2 200 mm and the inlet pipe diameter of 720 mm.Based on CFD numerical simulation method,and taking the average velocity and the uniformity of flow field as the indexes,the fluid distributions along the longitudinal section and the inlet cross section of the shell pass of the three kinds of external flow distributor have been studied.It is proved that the rational selection of the external flow distributor could improve the flow field uniformity of the shell pass of heat exchanger.The combination of the quantitative and qualitative analysis showed that the average velocity of the variable-cross-section circular-arc transition external flow distributor is relatively reasonable and the uniformity of the flow field is the best,thus presenting a suitable flow distributor structure.The study results are of great significance for the type selection of external flow distributor.%管壳式换热器壳程流场均匀分布能够改善传热效果,外导流筒的合理选型对流场均匀性有重要影响.然而,外导流筒结构多样,其选型设计多依靠经验,缺乏指导性方法.鉴于此,以筒体直径2 200 mm、入口接管外径720 mm的竖直管降膜式蒸发器换热段为研究对象,设计了外导流筒,建立了3种结构的三维实体模型.基于CFD数值模拟的方法,以平均速度和流场均匀性为衡量指标,研究了3种导流筒结构壳程纵截面和入口截面的流体分布效果,证明了外导流筒合理选型确实能够改善换热器壳程流场均匀性.定性结合定量分析得出:变截面圆弧过渡式外导流筒平均速度相对合理,流场均匀性最佳,是较适宜的导流筒结构.研究结果对外导流筒的选型设计具有重要意义.