A selection method of variable speed centrifugal pumps for maximum hydraulic efficiency

Abstract

Variable speed pumps (VSPs) are more energy efficient compared to other flow control methods such as throttling control valves. However, their selection process is not straightforward because the pump characteristics should be optimised against the load profile of the flow system for maximum hydraulic efficiency. This paper presents a VSPs selection method based on generic mathematical models of centrifugal pumps efficiency, characteristics and similitude, which enables the extension of this method to other types of turbomachines. This selection method results in a nonlinear algebraic equation that is solved numerically to obtain a reference flow rate that maximises the pumping system hydraulic efficiency. This reference flow rate is subsequently used to obtain the pump characteristic curves at all operating pump speeds. The results show that this method is fast, accurate and reliable. Because the developed method uses generic pump models rather than specific models from manufacturers’ databases, it enables the integration of VSP selection process in early engineering design phases of pumping systems.