Flow losses analysis in a mixed flow pump with annular volute by entropy production evaluation

Abstract

Mixed flow pumps with annular volute are widely used in thermal and nuclear power plants for transporting or circulating the coolant, and require a high amount of power for which a large amount of electricity is required. Thus, improving its efficiency is absolutely important. The flow losses in the mixed flow pump with annular volute influence the hydraulic efficiency directly and are investigated in detail using computational fluid dynamics (CFD) in this paper. The Reynolds-averaged Navier–Stokes equation, coupled with the SST k-ω turbulent model, is employed to simulate the unsteady turbulent flow using ANSYS CFX. The numerical simulation results have been verified with the experimental measurements. The entropy production evaluation using CFD is applied to reveal the internal loss distribution and the amount of power losses. The results show that the power losses produced by turbulence dissipation are dominant, and the power losses caused by viscous dissipation can be neglected in each component. The turbulence dissipation losses in the annular volute are much larger compared to the other components, and a major loss distribution can be observed around the diffuser outlet and the shoulder between the circular flow channel and the discharge pipe, which is caused by the flow impact and separation. Therefore, the annular volute will be the key component for optimization and has the potential to reduce losses. This study can help understand the flow loss mechanisms and can provide theoretical guidance for improving the hydraulic efficiency of mixed flow pumps.