Hybrid nanofluids flow in eccentric annuli under contracting and expanding wall motion

Abstract

Nanofluids have been developed as promising thermal transferal fluids due to their enriched thermophysical properties, despite contradictions in reported results and an incomplete understanding of their heat transfer mechanisms. The researchers attempted to employ hybrid nanofluid, which was created by suspending dissimilar nanoparticles in composite or mixture form, as part of their ongoing investigation into nanofluids. The purpose of employing hybrid nanofluid is to improve heat transfer significantly. Modified nanofluid model is the generalized form of hybrid nanofluid and simple nanofluid model. Utilizing a mathematical model, a comparative analysis of nanofluid $(A{l}_2{O}_3-H_{2}O)$, hybrid $(A{l}_2{O}_3,Cu-H_{2}O)$ and modified $(A{l}_2{O}_3,Cu,Ni-H_{2}O)$ nanofluids flow driven by contracting and expanding mechanism through eccentric annuli. Three distinct nanoparticles are introduced in this instance, significantly improving the base fluid's heat conductivity. For this analysis alumina, copper and nickel are treated as nano-particles and water as a base fluid. The model assumed here is pumping of water mixture filled with different nano-particles through circular eccentric cylinders and it is inspired due to the fact that thread injection is a likely technique for placing medical implants within the human body with least surgical trauma. The conversion of energy in the form of exothermic reaction is assumed to enhance the temperature of eccentric system. Similar to the structure of an artery, the outer cylinder contains a sinusoidal wave that travels down to its boundaries in the form of concentration and relaxation events, while the inner cylinder is invariant, solid, and flowing at a constant velocity. Long wavelength and low Reynolds number approximation is used for analytic solution. The governing non-linear partial differential equations are converted into ordinary differential equations by perturbation technique and are solved by mathematic software. Next we compared graphical significance of nanofluid $(A{l}_2{O}_3-H_{2}O)$, hybrid $(A{l}_2{O}_3,Cu-H_{2}O)$ and modified $(A{l}_2{O}_3,Cu,Ni-H_{2}O)$ nanofluids for friction forces on inner and outer cylinders, pressure gradient, pressure rise, temperature and velocity profiles for different values of solid volume fractions and average flow rate. At last, trapping boluses are plotted in the form of streamlines by varying inner cylinder radius. The finding indicated that the modified nanofluids enable wider operational flexibility in peristaltic pumps, with superior behavior in both thermal and flow regimes. Pressure gradient increases significantly with nanoparticle concentration modified nanofluids show up to 600 % enhancement compared to mono nanofluids. Temperature profiles peak highest for modified nanofluids, with a 40–60 % boost in thermal performance due to multi-metal synergy ($A{l}_2{O}_3$, $Cu$, $Ni$). Modified nanofluids show lowest friction in low-flow regimes and higher friction beyond G > 7.