导流装置对凸肋通道传热与流动的影响

Influence of Deflectors on Heat Transfer and Fluid Flow in Ribbed Channel

采用商用CFD软件Fluent对内插四种导流装置(上半圆弧,下半圆弧,圆柱型,斜板型)的凸肋通道传热和流动性能进行了数值模拟。分别研究了导流装置形状,导流装置位置对通道内流场、传热性能与流动阻力的影响。结果表明,与传统凸肋通道相比,内插导流装置的通道平均Nusselt数(Nu)提高了14.8%以上。斜板型导流装置的Nu最大,而圆柱型导流装置的阻力因子f最小。从流场及温度场分布可以看出,导流装置的引流作用使部分主流区流体流向凸肋下游的壁面,并与壁面发生了碰撞,减薄了壁面的热边界层,从而提高了传热速率。另外,导流装置向凸肋上游移动时,对传热的影响不明显;导流装置向凸肋下游移动时,流动附着点也随之移动,热边界层被破坏后重新发展,导致传热速率增加。比较导流装置不同位置的综合性能因子(TPF),位置I的效果最优。

The influence of 4 types of deflectors（Arc deflector, Inversed arc deflector, Rectangle deflector and Cylinder deflector） on heat transfer and fluid flow in ribbed channel was investigated by using commercial CFD software of Fluent 6.3. The effects of deflector shape and deflector location on fluid flow distribution, heat transfer and flow resistance were also investigated. The numerical results show that compared with conventional ribbed channel Nu number for ribbed channel with defectors is increased by more than 14.8%. The case with rectangle deflector provides the highest Nu value and the case with cylinder deflector shows the lowest f value. From the analysis of fluid flow and temperature distributions, fluids in the mainstream are induced by deflectors to the bottom wall between ribs. The thermal boundary layers are interrupted by deflecting fluid and fluid impingement on the wall, thus increases the heat transfer rate. On the other hand, the effect of deflector location on heat transfer performance can be ignored when deflectors are located at the upstream region near the rib, while the thermal boundary layers re-develop with the moving of flow attachment point when deflector location moving downstream. Location I shows the best overall thermal performance factor（TPF） by comparing with TPF values at different deflector locations.