Thermal Cooling and System Irreversibilities of A Divergent/Convergent Channel with The Bioconvection Flow of Non-Newtonian Nanofluid

The laminar bioconvection flow of a nanofluid in a convergent/divergent channel is computationally analyzed. The channel features impervious, adiabatic walls. A physics-based model couples the mass, momentum, and energy conservation equations. A thermal-hydraulic and entropy production analysis is performed using the first and second laws of thermodynamics to identify ideal parameters that maximize thermal performance while minimizing system irreversibility. Fluid flow, heat-mass transfer, motile microorganism density, and system entropy are investigated as functions of the channel angle. The governing equations are reduced via scaling and solved numerically using the Keller-Box method. Results indicate that higher Reynolds numbers and cross-viscosity reduce frictional drag, while motile density decreases with the Péclet number. Heat and mass transfer rates decline with increased Brownian motion, whereas thermophoresis shows opposing effects. Nanoparticle diffusion mitigates channel overheating, aiding thermal cooling. System irreversibilities dominate in narrower sections, and entropy generation near the wall increases with thermophoresis.