螺旋肋片自支撑换热器壳程性能数值分析

NUMERICAL ANALYSIS OF THE SHELL-SIDE PERFORMANCE OF HEAT EXCHANGER WITH HELICAL RIB TUBE

采用FLUENT软件分别对套管换热器和管束换热器的流场及传热和压力降特性进行数值模拟与分析,并与试验数据进行比较。结果表明,螺旋肋片强化传热的主要机理是螺旋肋片引起的螺旋流动使流体流速提高并产生二次流,减薄了速度边界层,促进了主流流体和边界层流体的掺混;换热管之间螺旋流动的相互影响进一步提高了换热器的传热系数;螺旋肋片的螺旋角和流体雷诺数对壳程努塞尔数和压降产生显著影响,应将螺旋角和雷诺数限制在一定的范围内。数值模拟结果与试验数据吻合较好。

In order to investigate the mechanism of enhancing heat transfer efficiency by helical rib,3D models of double tube and tube-bundle heat exchangers are set up respectively using FLUENT software. The characteristics of flow field, heat transfer and pressure drop at the shell-side are simulated and compared with the test data. Results show that the increase of heat transfer efficiency by helical rib is due to the generation of helical flow, which accelerates the velocity of fluid flow and generates secondary flow,as a result,the fluid mixing between the main body and the boundary layer is enhanced and the thickness of boundary layer is reduced. The interaction of helical flows among heat exchange tubes can further enhance the heat transfer coefficient of heat exchanger. The helical angle of helical rib and Reynolds number has significant influences on shell-side Nusselt number and pressure drop. It is proposed that the helical angle and Reynolds number should be confined to a proper range. The numerical simulated results agree well with the experimental data.