The heat transfer and pressure drop characteristics of SiO₂/water nanofluids flowing through a horizontal circular stainless steel tube equipped with free rotating swirl generators (FRSGs) at the entrance of a test tube are reported in this article. The experimental studies were performed with a Reynolds number ranging from 3500 to 13,000; volume concentrations of 0.5, 1, and 2 vol%; and inlet temperatures of 25, 30, and 35 °C, where a constant heat flux was imposed on a test tube. FRSGs made from aluminum, with three different twisted angles (30°, 60°, and 90°) and a length of 2.3 cm, were located at the entrance of the test tube. The results indicated that FRSGs had significant effects on heat transfer and pressure drop characteristics for the flow of both water and nanofluids in the tube. The Nusselt number increased with increasing volume concentration, inlet temperature, and Reynolds number. However, the friction factor of nanofluids flowing through FRSGs was significantly greater than that of water when the Reynolds number was lower than 6000. This is because FRSGs do not rotate under the given conditions. A maximum efficiency index of 1.57–1.7 was obtained when using SiO₂/water nanofluids with FRSGs at a volume concentration of 2 vol%, inlet temperature of 35 °C, and Reynolds number greater than 7000. On the other hand, the efficiency index value was lower than unity when the Reynolds number was lower than 7000 and with volume concentrations of 0.5 and 1 vol%. No significant differences were found among twisted angles of FRSGs on heat transfer, pressure drop, and efficiency index.

SiO ₂的传热和压降特性本文报道了水/纳米水流过水平圆形不锈钢管的现象，该水平不锈钢管在试管的入口处配备有自由旋转涡流发生器（FRSG）。实验研究的雷诺数为3500至13,000；体积浓度为0.5、1和2 vol％; 入口温度为25、30和35℃，在此温度下，恒定的热通量施加在试管上。由铝制成的FRSG具有三个不同的扭曲角度（30°，60°和90°），长度为2.3厘米，位于试管的入口。结果表明，FRSGs对水和纳米流体在管中的流动的传热和压降特性有显着影响。努塞尔数随体积浓度，入口温度和雷诺数的增加而增加。然而，当雷诺数低于6000时，流经FRSG的纳米流体的摩擦系数显着大于水。这是因为FRSG在给定条件下不会旋转。使用SiO时的最大效率指数为1.57–1.7₂ /水纳米流体，其中FRSGs的体积浓度为2 vol％，入口温度为35°C，雷诺数大于7000。另一方面，当雷诺数小于7000时，效率指数值小于1。体积浓度为0.5和1 vol％。FRSG的扭曲角之间在传热，压降和效率指数上没有发现显着差异。