Abstract

A horizontal double-tube counter-flow heat exchanger with and without twisted tape inserts (twist ratio of 3.2, 4, and 6) has been investigated experimentally using TiO₂-H₂O nanofluid. In this study, the heat transfer coefficient and friction factor of turbulent flow of TiO₂-H₂O nanofluid have been determined for Reynolds’ number varying from 5,000 to 25,000. Convective heat transfer coefficient for TiO₂-H₂O nanofluid (0.05% by vol.) is found to be higher than base fluid (4–6%). Also, an increase in the heat transfer coefficients up to 6%, 10.9%, 17.4%, and 23.4% are observed numerically for the 0.05%, 1%, 2%, and 3% volume concertation of nanoparticles of TiO₂. On the other hand, when TiO₂-H₂O nanofluid (0.05% by vol.) is investigated using twisted tape inserts of twist ratio 3.2, the heat transfer coefficient is found to be increasing by 45%. The variation of the heat transfer coefficient for different types of nanofluids such as; TiO₂-H₂O, Al₂O₃-H₂O, and CuO-H₂O with 1% concentration of nanoparticles (by vol.) has also been studied at different Reynolds’ numbers. The simulated results show no significant effect of the size (30 nm and 50 nm) of nanoparticles (TiO₂) on the heat transfer coefficient values of TiO₂-H₂O nanofluid at 0.05% volume concentration.

摘要

_{已经使用 TiO 2} -H ₂ O 纳米流体对具有和不具有扭曲带插件（扭曲比为 3.2、4 和 6）的水平双管逆流换热器进行了实验研究。在这项研究中，已经确定了雷诺数从5,000到25,000变化的TiO ₂ -H ₂ O纳米流体湍流的传热系数和摩擦系数。_{发现 TiO 2} -H ₂ O 纳米流体的对流传热系数（按体积计 0.05%）高于基础流体（4-6%）。_{此外，对于 0.05%、1%、2% 和 3% 的 TiO 2}纳米颗粒的体积协同作用，数值上观察到传热系数增加高达 6%、10.9%、17.4% 和 23.4%. 另一方面，当使用扭曲比为 3.2 的扭曲带插件研究 TiO ₂ -H ₂ O 纳米流体（0.05% 体积）时，发现传热系数增加了 45%。不同类型纳米流体的传热系数的变化，例如；纳米粒子浓度为 1%（按体积计）的TiO ₂ -H ₂ O、Al ₂ O ₃ -H ₂ O 和 CuO-H ₂ O 也在不同的雷诺数下进行了研究。模拟结果表明纳米颗粒（TiO _{2 ）的尺寸（30 nm 和 50 nm）对 TiO 2} -H ₂的传热系数值没有显着影响O 0.05% 体积浓度的纳米流体。