Single and multiple walled CNTs-TiO2 ternary hybrid nanofluid flow of Williamson fluid in an unsteady combined convective regime: An entropy analysis

A comprehensive study has been made on the unsteady combined convective flow of Williamson ternary hybrid nanofluid over a rotating sphere with multiple slips and entropy generation (EG). The carbon nanotubes with single (SWCNT) and multiwalled (MWCNT) are dispersed in the base fluid along with the titanium dioxide nanoparticles. The relevant coupled nonlinear partial differential equations (PDEs) are formulated using boundary layer approximations. The nonsimilar transformations convert the governing PDEs into nondimensional forms. The transformed equations are subjected to the Quasilinearization technique for linearization. Further, the implicit finite difference approach leads to discretizing the linearized equations. Incorporating CNTs-TiO2 ternary hybrid nanofluid leads to a higher heat transfer rate than single and two components nanofluids with the same volume fraction of 6%. The SWCNT-MWCNT Williamson hybrid nanofluid improves the energy transport rate by approximately 8% compared to the SWCNT Williamson nanofluid. The Williamson ternary hybrid nanofluid improves heat transfer strength by approximately 34% compared to the Williamson fluid. The comparison of the Newtonian ternary hybrid nanofluid (W=0) with the Williamson ternary hybrid nanofluid (W=0.5) reveals that the EG is minimum, and the Bejan number is more for the Williamson fluid than that for the Newtonian fluid. A fall in the EG is found near the sphere's surface for higher values of temperature difference ratio and velocity slip.

Automated summary

This study examines the unsteady combined convective flow of Williamson ternary hybrid nanofluid over a rotating sphere with multiple slips and entropy generation. The inclusion of carbon nanotubes and titanium dioxide nanoparticles in the base fluid results in higher heat transfer rates compared to single and two-components nanofluids at the same volume fraction. The SWCNT-MWCNT Williamson hybrid nanofluid shows an improvement of approximately 8% in energy transport rate compared to SWCNT Williamson nanofluid. The Williamson ternary hybrid nanofluid demonstrates a 34% enhancement in heat transfer strength compared to the Williamson fluid.