Flow and heat transfer analysis of an ionanofluid above a rotating disk undergoing torsion

Abstract

The convective heat transfer properties of traditional nanofluids and ionic liquid-based nanofluids (ionanofluids) are crucial in engineering applications such as heat exchangers, electronics cooling, and energy storage. Given the relevance of the rotating disk flow model in these applications, this study examines the boundary layer flow and heat transfer resulting from the torsional motion of a rough rotating disk, specifically considering ${\mathrm{Al}}_2{O}_3$ and $\mathrm{Cu}$ nanoparticles dispersed in water and the ionic liquid $\left[C_{4}mim\right]\left[N{\left(Tf\right)}_2\right]$ under a vertical magnetic field. The boundary value problem governing this flow is first shown to have a solution through a topological shooting method. Numerical integrations via a collocation method (SQLM) are then used to evaluate the flow and heat transfer characteristics. The results show that torque requirements decrease with the torsional exponent $m$, with water requiring more torque than $\left[C_{4}mim\right]\left[N{\left(Tf\right)}_2\right]$ to sustain rotation. Notably, $\left[C_{4}mim\right]\left[N{\left(Tf\right)}_2\right]$-based fluids exhibit a higher heat transfer enhancement than water. Lamina-shaped nanoparticles deliver the highest heat transfer rates compared to other shapes (spherical, cylindrical, and columnar). Furthermore, the entropy generation number $NS$ declines with increased azimuthal slip parameter ${\lambda }_2$, thermal slip parameter ${\lambda }_3$, and torsional exponent $m$. This indicates that entropy generation can be controlled by incorporating torsional motion with thermal slip on an anisotropic rough disk, while also carefully selecting other governing parameters.