自转螺旋扭带管内三维流动与传热数值模拟

3D numerical simulation of fluid flow and heat transfer in self-rotating twisted-tape-inserted tube

建立了内置自转螺旋扭带管的三维流动模型,采用RNGkε湍流模型对管内流场进行了数值模拟,得到了流体的流动和传热特性.研究表明:自转扭带管内的流动是复杂的三维螺旋流动.流体在扭带与管内壁环缝区域的轴向速度比光管的大;流体在与扭带宽度等直径范围内的切向速度随半径的增大而增大,流体在扭带与管内壁环缝区域内也存在明显的切向速度,但随半径的增大而减小;而光管内流体的流动只有随机的切向运动,且其切向速度要比扭带管内的切向速度小2个数量级;扭带管流体的径向速度和湍流度也比光管的大.扭带管内流体近管壁区域轴向、切向、径向速度和湍流度的加大,强化了管内的对流传热,其表面传热系数大于光管.另外,速度场的模拟值与激光测试值进行了比较,二者吻合较好.

A three-dimensional fluid flow model for a self-rotating twisted-tape-inserted tube was presented. The RNGAk-ε turbulent model was used to simulate the fluid flow and heat transfer in the selfrotating twisted-tape-inserted tube. The eharaeteristies of fluid flow and heat transfer in the self-rotating twisted-tape-inserted tube were determined. Numerieal simulation results showed that the fluid flow was a eomplex three-dimensional helix flow in the self-rotating twisted-tape-inserted tube. Axial veloeity was higher in the annular area near the tube wall than that in the smooth tube; the tangential veloeity in the diameter area eorresponding to the width of twisted tape inereased with the radius. The tangential motion in the annular area between the twisted tape and tube wall was obvious, but the tangential veloeity deereased with the radius. However, the tangential motion of the fluid in the smooth tube was only stoehastie, and the tangential veloeity was smaller by two orders of magnitude. The radial veloeity and turbulenee intensity were also larger than those in the smooth tube. Due to inerease of the axial veloeity, tangential veloeity, radial veloeity and turbulenee intensity, the eonveetion heat transfer of the fluid wasstrengthened and the surface heat transfer coefficient for the self-rotating twisted-tape-inserted tube was larger than that of the smooth tube. In addition, numerical simulation results of the velocity field were compared with the experimental data measured by Laser Doppler Velocimeter （LDV） system. The numerical simulation results showed reasonably good agreement with the experimental data.