▎ 摘　　要

The second law performance of the ecofriendly graphene-based nanofluid inside the tubes fitted with novel rotary coaxial cross double-twisted tape (RCCDTT) is studied. Indeed, this study examines the effects of using both active and passive heat transfer enhancement methods simultaneously. Several weight fractions are examined and effects of the twisted ratio are also considered. The combination of these two techniques results in great decrement in the total entropy generation and exergy destruction, such that at weight fraction of 0.025% and twisted ratio of 3.5, the thermal entropy generation decreases up to 80% by rising the angular velocity from 0 to 900 rpm. Increasing the concentration results in the less irreversibility and the maximum decrement in the exergy destruction rate is about 24%. Moreover, the twisted ratio increment augments the entropy generation caused by heat transfer. The entropy generation due to the friction has a minute contribution and increases slightly by rising the angular velocity and weight fraction. The second law efficiency has ascending trend by the weight fraction increase and profoundly augments with increasing the angular velocity. The highest second law efficiency is attained 0.935 at concentration of 0.1%, angular velocity of 900 rpm, and twisted ratio of 2.5.