Entropy–heat transfer coupling in vibrational non-Newtonian nanofluid flow.

This study examines the combined effects of heat transfer and entropy generation in non-Newtonian nanofluid flow subjected to mechanical vibration within a cylindrical pipe. Using the volume of fluid method, the impacts of vibrational parameters—amplitude, frequency and Reynolds number—are analysed under two thermal boundary conditions: constant heat flux (HF) and constant wall temperature (WT). While Vibration boosts convective heat transfer through increased radial mixing and flow instability, it also influences entropy Generation by changing the balance between thermal and viscous irreversibility. At a frequency of 20 Hz and an amplitude of 5 mm, the entropy generation rate decreased from 0.58 to 0.28 under WT conditions, indicating enhanced thermodynamic performance. A sensitivity analysis shows amplitude as the most influential parameter affecting both heat and entropy transport. The results demonstrate that selecting optimal vibrational parameters can simultaneously improve heat transfer and reduce irreversibility, providing a second-law-based approach for designing energy-efficient thermal systems with nanofluids. [ABSTRACT FROM AUTHOR]