插入物对新型换热器传热性能的影响

Effect of Inserts on Heat Transfer Performance of New Heat Exchanger

在新型换热器——自支撑矩形缩放管换热器的基础上,利用Fluent数值模拟方法,研究了在其壳程内分别插入传统插入物（旋流片）和新型插入物（折板）后传热性能与流动特性的变化,研究的雷诺数（Re）变化范围为27900~41900。结果表明,与空管缩放管换热器相比,插入旋流片和折板的换热器壳程的传热系数随Re的增大分别增加了31.07%~33.08%和38.01%~46.74%;插入物在提高传热系数的同时也引起了通道内压降的增大,插入旋流片和折板时通道内压降分别增加了69.32%~77.42%和68.49%~87.16%;插入折板后壳程通道内的综合传热性能最好,其次是插入旋流片的,无插入物时则最差。提高换热器传热性能的关键是要改善通道两侧缩放管处的传热性能,减小速度场与温度场间的协同角是增强换热器传热性能的一项重要措施。

Based on the new heat exchanger, self-support rectangle converging-diverging tube bundle heat exchanger, the turbulent heat transfer and fluid flow characteristics of the heat exchanger with different inserts were studied in the Reynolds number range of 27900 to 41900 by 3-D numerical simulations with Fluent software, and compared to that of the baseline configuration （without insert）. The used inserts included regularly spaced twisted-tape （RSTT） and baffle plate （BP）. The results showed that compared with the baseline case, the air-side heat transfer coefficients of the two enhanced cases were improved by 31.07%--33.08% and 38.01%--46.74%, with an associated pressure drop penalty increase of 69.32%--77.42% and 68.49%--87.16%, respectively. The BP case obtained the best overall performance, followed by the RSTT case, and the baseline case was the worst. The key point of enhancing heat transfer of shell side was to improve the heat transfer performance on converging-diverging tube. The reduction in the average intersection angle between the velocity vector and the temperature gradient was one of the essential measures to enhance heat transfer performance of heat exchanger.