15 Affinity laws relate to the characteristics of pumps operating at different speeds, and in a 16 water distribution context are usually used to predict the pump curve of variable speed pumps 17 (VSPs). VSPs can adjust the pump curve so as to meet the network requirements more 18 efficiently with resultant savings of energy. The estimation of the effectiveness of a VSP is 19 based on hydraulic simulations, where the behaviour of VSPs is described using the affinity 20 laws. The affinity laws,

more »

... owever, contain approximations, as they do not take into account 21 factors that do not scale with velocity. In particular, the approximation inherent in the affinity 22 law that computes power and efficiency can produce a misleading result, especially for small 23 size pumps. The research reported in this paper estimates the error in efficiency for a wide 24 range of pump sizes and tests the use of the formula proposed by Sarbu and Borza (1998) as 25 1 an alternative to the affinity law. Results show that a better estimation can be achieved for the 26 efficiency of small and medium size pumps. Moreover the formula can be easily 27 implemented in hydraulic solvers. 28 29