A Model for Analyzing Flow Transients in a Single Closed Loop

A mathematical model is developed upon which the velocity of flow during a centrifugal pump failure transient is determined analytically without the use of pump characteristics’ curves. The influence of the two most important parameters, kinetic energy in the piping system and kinetic energy of the pump, are considered in the form of a ratio called hereafter an effective energy ratio. The results show that the effect of a mechanical friction loss on the flow rate is very small in the early stage of pump failure transient, and the time of two-third decay of the flow is not affected very much by the friction loss. However, this effect is larger in the later stage of the flow decay. Therefore the time when the flow rate becomes zero, depends very much on the estimation of this loss. Good agreement is noted when the results of the analytical method are compared with those obtained by the use of experimental characteristics’ curves. The model is also used to analyze the transient during a fast startup. Also further comparison of the analytical model with the collected flow transient experimental data show a very good agreement.