Optimal Pipe Sizing and Operation of Multistage Centrifugal Pumps for Water Supply

Abstract

The operation of multistage pumps transporting water from the source to the delivery point requires balancing of the pressure at the junction of the pump and pipeline according to their characteristics. In this paper, nonlinear optimization models are developed to minimize the total annual cost for selecting the sizes of the pipelines in series and parallel connections of pumps taking water from one or more sources. The models are based on life cycle cost analysis, including replacement cost and escalating energy cost factors. The combined characteristic equations of the pumps in series and parallel connections are obtained using the characteristic equation of a single-stage pump. The constraints are imposed for the pressures at the junctions of the pipeline, with the pumps having different characteristics especially drawing water from different sources. The discharges of the pumps are regulated automatically according to the pressures adjusted at the junctions due to the resistance developed by the optimally designed pipe sizes. The requirements of the desired efficiency also are considered constraints in the models. The applicability of the developed models is illustrated through design examples to obtain optimal discharge and pipe sizes from a single water source for series and parallel connections. Also, the examples are solved to obtain the optimal pipe sizes and discharges from different pumps with the same and different characteristics and drawing water from multiple sources.