Abstract

Al₂O₃–water nanofluids along with stationary and rotating twisted tape inserts are used to increase the rate of heat transfer in a plain tube. The simulations are conducted through varying the design parameters including angular velocity of twisted tape, Reynolds number and nanofluid volume concentration. It is found that inserting a twisted tape inside a tube substantially increases the heat transfer coefficient and friction factor compared to the plain tube. Compared to the stationary twisted tape, the rotating twisted tape exhibits a great potential to modify the average Nusselt number by about 32.8–39.6% at Reynolds number of 250, depending on the angular velocity. This is attributed to the formation of conical tornado-shape structures in the flow pattern, causing more effective mixing in the flow. By increasing the Reynolds number, the enhancement in the average Nusselt number increases in stationary and decreases in rotating configurations compared with the plain tube. To assess the tradeoff between heat transfer enhancement and pressure loss penalty, the performance evaluation criterion (PEC) is calculated. The results suggest that the highest PEC is obtained at Reynolds number of 250, nanofluid volume concentration of 3% and the highest studied angular velocity.

摘要

铝₂ O ₃– 水纳米流体以及固定和旋转的扭曲带插件用于提高普通管中的传热速率。模拟是通过改变设计参数进行的，包括扭带的角速度、雷诺数和纳米流体体积浓度。发现与普通管相比，在管内插入绞合带显着增加了传热系数和摩擦系数。与静止的扭带相比，旋转扭带在雷诺数为 250 时显示出将平均努塞尔数修改约 32.8-39.6% 的巨大潜力，具体取决于角速度。这归因于流动模式中锥形龙卷风形状结构的形成，导致流动中更有效的混合。通过增加雷诺数，与普通管相比，平均努塞尔数的增加在静止时增加，而在旋转配置中减少。为了评估传热增强和压力损失损失之间的权衡，计算了性能评估标准 (PEC)。结果表明，在雷诺数为 250、纳米流体体积浓度为 3% 和研究的最高角速度时获得最高的 PEC。