Fluid flow and heat transfer of \(\text {Al}_2\text {O}_3\)/water and CuO/water nanofluids with 1–3\(\%\) volume fraction of nanoparticle in a clockwise–counter-clockwise twisted square duct \((T_{CW-CCW}SD)\) are numerically simulated using the \(\kappa --\epsilon \) turbulence model. Nanofluids flow through a twisted duct with uniform wall temperature boundary conditions, twist ratios of 8.5, 11.5, 16.5 and Reynolds numbers of 100–20,000 are studied numerically. The results show that reducing twist ratios from 16.5 to 8.5 improves heat transfer significantly. In comparison with the results obtained using simple base water, the average percentage increase in Nusselt number is around 0.1–0.5\(\%\) higher at 1\(\%\) volume concentration of \(\text {Al}_2\text {O}_3\) nanoparticle and 0.5–1\(\%\) increment in average Nusselt number is observed for 1\(\%\) concentration of CuO. It was also discovered that increasing the concentration of \(\text {Al}_2\text {O}_3\) nanoparticle in normal water from 2–3% reduces heat transfer enhancement, whereas the CuO nanoparticle enhances heat transfer coefficient for the same volume fraction of nanoparticle, and this enhancement is found to be within 0.5%. To compare twisted and straight ducts, an enhancement factor or quantity is calculated based on constant pumping power criteria. The enhancement factor is used to prioritize the twisted square duct selections. Performance evaluation criteria show that the twisted duct performs well up to the Reynolds number of 2000, while beyond the Reynolds of 2000, this twisted duct is not suitable due to strong presence of reverse flow. It is recommended to use twisted clockwise–counter-clockwise square duct for the Reynolds number till 2000. Correlations involving swirl parameters such as twist ratios, percentage of volume fraction of nanoparticles and Reynolds number are also proposed separately for friction factor and Nusselt number.

\(\text {Al}_2\text {O}_3\) /water 和 CuO/water 纳米流体的流体流动和传热，其中纳米粒子的体积分数为1–3 \(\%\)顺时针 - 逆时针扭曲的方形管道\((T_{CW-CCW}SD)\)使用\(\kappa --\epsilon \)湍流模型进行数值模拟。纳米流体流过具有均匀壁温边界条件、扭曲比为 8.5、11.5、16.5 和雷诺数为 100-20,000 的扭曲管道进行了数值研究。结果表明，将扭曲比从 16.5 降低到 8.5 可以显着改善传热。与使用简单基水获得的结果相比，努塞尔数的平均增加百分比约为 0.1–0.5 \(\%\)在1更高\（\％\）体积的浓度\（\ {文本的Al} _2 \文本{ö} _3 \）纳米颗粒和0.5-1 \（\％\）在平均努塞尔数增量观察1 \（ \%\) CuO 的浓度。还发现增加\(\text {Al}_2\text {O}_3\)普通水中的纳米颗粒从 2-3% 降低传热增强，而 CuO 纳米颗粒提高纳米颗粒的相同体积分数的传热系数，并且发现这种增强在 0.5% 以内。为了比较扭曲的和直的管道，基于恒定的泵送功率标准计算增强因子或数量。增强因子用于确定扭曲方形管道选择的优先级。性能评价标准表明，扭曲风管在雷诺数2000以下表现良好，而超过2000雷诺数时，由于逆流的存在，这种扭曲风管不适用。对于雷诺数直到 2000 年，建议使用顺时针-逆时针扭转方管。