恒热流工况下螺旋管内层流换热性能数值模拟

在恒热流工况下，数值模拟雷诺数为200～1000，无量纲螺距为0．1～0．2，曲率为0．1～0．3的螺旋管内不同截面上的温度场分布和速度场分布以及雷诺数、曲率和无量纲螺距对轴向不同截面上平均努谢尔特数、平均摩擦系数以及总熵产的影响规律。结果表明，随着转角增大，二次流作用加强，且垂直于轴向截面的最大速度向管的外侧移动，而温度分布出现两个Dean涡胞；轴向截面平均努谢尔特数和摩擦系数以及总熵产随雷诺数、曲率和螺距的变化呈现不同的规律；与曲率相比，螺距对热力性能的影响程度相对较小；且流动引起的熵产和传热引起的熵产相比可忽略不计。

Numerical Simulation of Thermal-Hydraulic Characteristics Through a Helical Coiled Tube With Constant Heat Flux for Laminar Flow

A numerical method for simulating the developments and distributions of heat transfer and flow fields was proposed. The effects of Reynolds number, curvature ratio, and coil pitch on the average friction factor, average Nusseh number at different axial cross--sections and the total entropy generation rate in a helical coiled tube with uniform heat flux was presented when Reynolds number is 200-1 000, dimensionless pitch 0.1-0.2 and dimensionless curvature ratio 0. 1-0.3. The results show that the effect of the secondary flow is enhanced with the increase of turning angle, the maximum velocity perpendicular to axial cross section shifts toward the outer side of helical coiled tube and two Dean roll cells appear with the increase of axial turning angle. Furthermore, the average friction factor, average Nusselt number at different axial cross-- sections and the total entropy generation rate present different characteristics when the Reynolds number, curvature ratio and pitch change. Compared with the curvature ratio, the pitch has relatively little influence on convective heat transfer performance and the total entropy generation. In the meantime, the entropy generation caused by viscous flow is much less than that caused by heat transfer and can be neglected.