内置折边扭带圆管内三维流动与传热数值模拟

为研究烟气在内置扭带管内流动和强化传热特性,以螺旋扭带管和折边扭带管为研究对象建立烟气流动与传热三维数值模型,模型中对近壁面采用增强壁面函数法,并考虑低雷诺数和旋转流对湍流黏度的影响。与圆管相比Re=2300～5000内螺旋扭带管Nu提高21%～24％;折边扭带管Nu提高25%～32％。折边扭带管流动阻力ΔP为12～57Pa,比螺旋扭带管ΔP增加10%～18％。折边扭带管传热和流动性能比φ为120%～126％。内置折边扭带管强化传热的原因是具有沿流向以折边长度为周期的增速和减速。

3D numerical simulation of fluid flow and heat transfer in a circular tube with edge-fold-twisted-tape inserts

A 3D numerical simulation was carried out to study the fluid flow and heat transfer enhancement characteristics of flue inside a circular tube with spiral-twisted-tape(STT) and edge fold-twisted tape(ETT) inserts. An enhanced wall treatment, a differential formula for the effective viscosity to account for the low Reynolds number effects and modification for moderate swirling flow were adopted. Rearranged from 2 300 to 5 000, the Nu of tube with STT inserts is 21% ～ 24% higher than that of circular tube, and the Nu of tube with ETT inserts is 25% ～ 32% higher than that of the circular tube. The pressure drop of the tube with ETT inserts is from 12 Pa to 57 Pa, which is 10% ～ 18% higher than that of STT inserts. The thermal-hydraulic performance of ETT is from 120% to 126%. The heat enhancement reasons of ETT inserts is the characteristic of periodic velocity increases and decreases within an edgefold length.