Influence of non-Newtonian fluid viscosity on the performance and energy loss mechanisms of centrifugal pumps

Centrifugal pumps often suffer from performance degradation when conveying non-Newtonian fluids in the petrochemical industry, owing to the special rheological properties of the medium. Based on the entropy generation theory, this paper investigates the flow characteristics of centrifugal pumps conveying non-Newtonian fluids with different viscosities via rheological tests, numerical simulations, and experimental verification and analyzes the distribution of energy loss and its formation mechanisms. The results show that an increase in fluid viscosity leads to a rise in total entropy generation loss, a decrease in pump head and efficiency, and a shift in the dominant mechanism of entropy generation loss. Specifically, under high-viscosity conditions, wall entropy generation becomes the primary form of energy loss, accounting for 99%. As viscosity decreases, turbulent entropy generation emerges as the dominant energy loss mechanism, accounting for 69%, while the proportion of viscous entropy generation remains below 5%. Mechanism analysis reveals that under high-viscosity conditions, the shear-thinning property of non-Newtonian fluids increases the velocity gradient within the boundary layer, intensifying the shear effect on the wall and causing wall entropy generation to dominate energy loss. At low viscosities, the turbulent pulsation of the fluid is enhanced, and phenomena such as disturbances in the blade wake, flow separation on the blade suction surface, and recirculation in the impeller passage are exacerbated, promoting turbulent entropy generation to become the dominant factor. This study uncovers the unique energy dissipation law of non-Newtonian fluids in centrifugal pumps, providing a theoretical reference for the optimal design of chemical centrifugal pumps.