螺旋套管式换热器螺纹强化管程传热研究

Study on Heat Transfer Enhancement of Screw Thread in the Tube Side of Spiral Double-pipe Heat Exchanger

基于实际工程应用,采用CFD软件,建立了内管为螺纹管的新型螺旋套管式换热器的三维实体模型,并使用管程流体与壳程流体耦合计算的方法进行模拟计算,重点分析了螺纹槽高和槽距等结构参数对管程流体流动与传热特性的影响。结果表明:螺纹的扰流和导流作用,改变了管程螺旋通道横截面上的二次流结构,除在横截面外侧区域形成一个不规则主涡外,还在截面内侧区域的近螺纹处产生了大小不一的附加涡旋。主涡和附加涡共同作用加剧了壁面和中心区流体的热质交换,强化了换热效果。在研究范围内(Re=8000~40000),螺旋套管式换热器内管采用螺纹管与内管采用光管相比换热效果提高了约36%~143%。螺纹槽高及槽距对管程流体传热影响较大,Nu和f随槽高的增加而增加,随槽距的增大而减小。

Based on the actual engineering application,using CFD software,the three-dimensional entity model of new spiral tube heat exchanger with thread inner tube was established,and simulation calculation was carried out by using the coupling calculation method of tube-side fluid and shell-side fluid,and the influence of structural parameters such as thread groove height and groove spacing on the fluid flow and heat transfer characteristics of the tube side was mainly analyzed.The results showed that the secondary flow structure of the spiral passage cross section was changed by the disturbance and diversion of the thread,and not only an irregular main vortex was formed in the outer part of the cross section,but also additional vortices of different sizes were generated in the inner part of the cross section near the thread.The interaction of main vortex and additional vortex intensified the heat and mass exchange between the wall and the central region and strengthened the heat transfer effect.In the research range(Re=8000~40000),the heat transfer effect of spiral tube heat exchanger using threaded tube was improved by 36%~143%compared with that using light tube.The height and distance of the threaded groove had great influence on the heat transfer of the fluid in the pipe.Nu and f increased with the increase of the height of the groove,but decreased with the increase of the distance of the groove.