螺纹槽管传热和流体阻力的数值模拟

对螺纹槽管在恒壁温和雷诺数(Re)5000～35000范围内空气的换热性能和压降进行了数值研究.分别对25种不同几何参数的螺纹槽换热管换热性能和压降与同参数的光滑管进行了对比分析.结果表明,螺纹槽管的换热性能显著强于光滑管,同时压降也不同程度地高于光滑管;其中螺纹槽深度对换热性能和压降的影响大于螺纹槽间距,二者存在相互影响,呈现了最优区间原则.最大平均努赛尔数出现在Re=5000,几何参数螺纹深度/内径(dl/D)=0.25,螺纹间距/内径(pl/D)=0.5时,是光滑管的3.1倍.最大综合换热性能指标(performance evaluation criteria,PEC)为1.404,出现在Re=5000,几何参数dl/D=0.15,pl/D=1时,此时螺纹槽管的换热能力是普通光滑管的1.8倍,摩擦因子是普通光滑管的2.25倍.从整体雷诺数范围考虑,最佳几何参数为dl/D为0.14～0.18,pl/D为0.8～1.2.

Numerical investigation of heat transfer and fluid resistance in spirally fluted tubes

In this paper, the heat transfer performance and pressure loss of air in the range of constant wall temperature and Reynolds number ranging from 5000-35000 are numerically studied. The heat transfer performance and pressure loss of spirally fluted tubes with 25 different geometric parameters were compared with smooth tubes. The results show that the heat transfer performance of the spirally fluted tube is significantly better than that of the smooth tube, and the pressure loss is also higher than that of the smooth tube in varying degrees. The influence of the depth of the flute on the heat transfer performance and pressure loss is greater than that of the flute pitch, and there is interaction between the two, showing the optimal interval principle. The maximum average Nusselt number appears at Re = 5000, geometric parameters dl / D = 0.25, pl / D = 0.5, which is 3.1 times of smooth tube. The maximum PEC value is 1.404, when Re = 5000, geometric parameters dl / D = 0.15, pl / D = 1, the heat transfer performance of the spirally fluted tube is 1.8 times than the smooth tube, and the friction factor is 2.25 times than the smooth tube. Considering the overall Reynolds number range, the optimal geometric parameters are dl / D = 0.14 to 0.18, pl / D = 0.8 to 1.2.