Exergy destruction within a centrifugal water pump

Abstract

Understanding the loss generation mechanisms in water pumps is a vital step in decarbonising our built environment, and achieve sustainable cities and communities. In this paper, loss generation mechanisms in a centrifugal pump are quantified by performing exergy analysis with unsteady Reynold Averaged Navier Stokes simulations (uRANS). Exergy analyses are performed at various operational conditions for a commercially available pump and its ideal version that has zero surface roughness. Numerical results are used to derive mathematical expressions to describe exergy destruction rates as functions of normalized flow rates. These expressions provide insight on how and where losses are generated within a centrifugal pump, and how loss generation mechanisms are affected by the flow rate. Results show that 80% of the losses are generated within the impeller, intersection and volute, whereas secondary flows through the deadzone and leakage paths have insignificant contribution to the total losses even though mass flow rate through these paths are considerable. The exergy destruction rate equations derived here, have the potential to replace the semi-empirical estimations of losses in traditional turbomachinery design methodologies and serve as a tool to develop a novel knowledge-based turbomachinery design methodology.