Entropy-production-based mapping of irreversible energy loss mechanisms in a centrifugal blood pump

Energy loss in centrifugal blood pumps affects hydraulic efficiency, heat generation, and hemocompatibility. Conventional pressure-drop and efficiency analyses primarily characterize global hydraulic performance but provide limited insight into the spatial origins and underlying mechanisms of local energy loss. In this study, an entropy-production-based framework was established to map irreversible energy-loss mechanisms in a centrifugal blood pump. The numerical model was validated by grid-independence testing and by comparison with experimental data. The results show that, unlike many industrial centrifugal pumps, energy loss in this blood pump is governed mainly by internal velocity gradients and shear-driven dissipation. Viscous entropy production accounts for 63.6%–85.4% of the total entropy production, whereas turbulent and wall entropy production contribute 9.77%–32.6% and 3.85%–4.82%, respectively. Regionally, the impeller is the dominant loss source, contributing 58.9%–74.2%, followed by the volute (24.3%–38.0%) and the inlet (0.53%–3.12%). Different pump subdomains possess distinct irreversible-loss mechanisms. In the inlet, secondary-passage backflow induces inlet recirculation and enhances turbulent entropy production under low-flow conditions. In the impeller, loss is governed by inlet-jet deflection, blade-surface separation, and rotor–stator shear. In the volute, the dominant loss mechanism evolves from near-tongue viscous shear to high-flow turbulent dissipation associated with Dean-type vortices and outlet-pipe recirculation. The narrow secondary flow path acts as a shear-dominated rotor–stator clearance, resulting in substantially higher viscous entropy production than in other regions. These findings reveal the mechanistic link between local flow structures and high entropy production, providing a foundation for hydraulic-loss reduction and local flow optimization in centrifugal blood pumps.