Effects of shear-thinning rheological properties on the energy loss characteristics of a biomass mixing vessel.

This article focuses on investigating the irreversible energy losses in mixing propellers used in anaerobic digestion (AD) systems, emphasizing the effects of fluid rheology and operating conditions through entropy generation theory. Using computational fluid dynamics (CFD) validated by experiments, the study analyzes energy dissipation mechanisms in shear-thinning non-Newtonian fluids modeled by a power law, revealing that energy losses predominantly occur in the propeller region, especially in blade sections 3–5. The findings indicate that rotation speed is the primary factor influencing viscous diffusion and total mechanical energy loss, while rheology significantly affects hydraulic losses at higher fluid concentrations, leading to reduced mixing efficiency and increased specific power consumption. Entropy generation analysis shows that turbulence and viscous diffusion account for over 98% of energy dissipation, with wall entropy being negligible, and highlights the importance of optimizing propeller blade design to enhance energy transformation and fermentation performance in AD systems.