错位角对管内双螺旋扭带层流换热特性的影响

The Effect of Dislocation Angle on the Heat Transfer Characteristics of Double Helix Twisted Tapes under the Laminar Condition in Circular Tube

为了提高管内层流换热性能,根据螺旋扭带的传热强化机理开发了双螺旋扭带作为管内扰流元件.在管内双螺旋扭带间隙比和长径比不变的情况下,通过数值模拟对内置不同错位角的双螺旋扭带在Re=100~1 200范围内的管内层流换热与流动特性进行研究.结果表明:在Re<500情况下错位角为0°的连续扭带Nu最大;当Re=500~1 200时,Nu分别在错位角为60°和错位角为0°达到最大值和最小值,前者比后者大2%~12%;阻力系数f在Re=100~1 200范围内随雷诺数的增大而减小,随扭带错位角的增大而增大;当100<Re≤900时,错位角为0°对应的强化传热比PEC最大,而在Re>900情况下,PEC在60°错位角最好,Re>500情况下,90°错位角的PEC值最小,始终小于其它错位角,在双螺旋扭带结构设计中应引起注意.

In order to improve the performance of laminar heat transfer in a tube, double helix twisted tapes were designed. Based on the same central clearance ratio and length-diameter ratio, numerical study was performed on the laminar heat transfer and fluid flow characteristics in circular tubes inserted with different double helix twisted tapes which have different dislocation angles with Reynolds number（Re） changing from 100 to 1 200. The results show that Nusselt number（Nu） is the highest for the case with 0° dislocation angle under lower Reynolds number （Re） ;When the Re = 500 - 1 200, the largest and smallest Nusselt numbers are reached at the 60°and 0°dislocation angle respectively, and the difference varies from 2 % to 12 % ;The friction factor （ f ） grows with the increase of the dislocation angle;When the Re〈〈. 900, the value of performance evaluation criterion（PEC） is the highest for the case with 0~ dislocation angle ;but for larger Re ,the PEC performs best at the 60° dislocation angle. When the Re 〉 500,90° dislocation angle has the lowest PEC.