内置扭带管Cu-水纳米流体的流动和传热特性

Flow and Heat Transfer Characteristics of Cu-water Nanofluids in Twisted-Tape Inserts in Tubes

为了研究纳米流体在内置扭带管表面传热特性及流动特性,设计并建立一套纳米流体表面传热实验系统,Reynolds数(Re)在2 000-7 000的范围内,分别对质量分数为0.1%,0.3%和0.5%的Cu-水纳米流体在不同扭转比的内置扭带管中的传热特性进行实验研究。结果表明:随着Re增加,Cu-水纳米流体和去离子水的沿程阻力系数均减少;水的沿程阻力系数小于Cu-水纳米流体,内置扭带管的沿程阻力大于光管,且随着扭转比的增大而减少;Nusselt数(Nu)随Re和纳米颗粒质量分数的增大而增大;Cu-水纳米流体的Nu比水高,质量分数为0.5%的Cu-水纳米流体在Y=3.5与Y=5.5的内置扭带管的增强幅度分别为2.29与2.14;内置扭带管的Nu比光管大,且随扭转比增大而减少。

In order to study the heat transfer characteristics of nanofluids in twisted-tape inserts in tubes, the heat transfer experimental system are designed and built, in the range of 2000 - 7000 of the Reynolds number, respectively for the nanofluids Cu-water in the mass fraction of 0.1% ,0.3% ,0.5% heat transfer characteristics of twisted-tape inserts in tubes. The results of experiments show that the friction factor decreased as the Reynolds number increased. The friction factor of the nanofluids was higher than the friction factor of water. The friction factor of twisted tape insert pipe was higher than the friction factor of plain tube, and the friction factor decreased as the twist ratio increased;The Nusseh number increased with the Reynolds number; The Nusselt number of the nanofluids increased with concentrations of nanoparticles; the Nusselt number of Cu- water nanofluids is higher than the Nusseh number of water. The enhancement with Cu-water nanofluid of 0. 5 % mass fraction for twist ratio of 3.5 and twist ratio of 5.5 is 2.29 and 2.14 respectively ; the Nusseh number of twisted tape insert pipe was higher than the plain tube, and the Nusselt number decreased as the twist ratio increased.