Abstract

In this study, heat transfer, flow characteristics, and entropy generation of turbulent TiO₂/water nanofluid flow in the spiral coil tube were analytically investigated considering the nanoparticle volume fraction, curvature ratio, flow rate and inlet temperature between 0.01–0.05 percent, 0.03–0.06, 1.3–3.3 l/min, and 15–27 °C, respectively. Results showed that the augmentation of the nanoparticle volume fraction increased the Nusselt number and friction factor up to 11.9% and 1.1%, respectively, while it reduced the entropy generation number up to 10.9%. Reducing the curvature ratio led to a maximum of 11.1% increase in the Nusselt number, while it resulted in a 5.6% increase in the entropy generation number. A decline in the inlet temperature from 21 °C to 15 °C proceeded a 28.4% and 7.1% increase in the heat transfer and pressure drop, respectively. The total entropy generation reduced with increasing nanoparticle volume fraction. For a low Reynolds number, a decrease in the curvature ratio led to a reduction in the total entropy generation, while reducing the curvature ratio was detrimental for a high Reynolds number. Analytical relations for optimum curvature ratio and optimum Reynolds number were derived. For the range of parameters studied in this paper, a range of optimum Reynolds number from 9000 to 12,000 was proposed.

摘要

在本研究中，湍流 TiO _{2 的}传热、流动特性和熵产生考虑纳米颗粒体积分数、曲率比、流速和入口温度在 0.01–0.05%、0.03–0.06、1.3–3.3 l/min 和 15–27 °C 之间，对螺旋盘管中的 /water 纳米流体流动进行了分析研究，分别。结果表明，纳米颗粒体积分数的增加使努塞尔数和摩擦系数分别增加了 11.9% 和 1.1%，而熵生成数减少了 10.9%。降低曲率比导致努塞尔数最多增加 11.1%，同时导致熵生成数增加 5.6%。入口温度从 21°C 下降到 15°C，传热和压降分别增加了 28.4% 和 7.1%。总熵产生随着纳米颗粒体积分数的增加而减少。对于低雷诺数，曲率比的降低导致总熵产生的减少，而降低曲率比对于高雷诺数是有害的。推导出最佳曲率比和最佳雷诺数的解析关系。对于本文研究的参数范围，提出了一个从 9000 到 12,000 的最佳雷诺数范围。