Question

its diagram show relationship between the head and flow of CF pump in matching pump to system requirements

how did i know the point b

i need to know the way for knowing it

Efficiency HeadHead Optimal Point Flow

Answer 1

EfficiencyhGrap shown in the image are for the Head Vs Flow and Efficiency Vs Flow (Discharge) for particular speed and Head Head diameter of impeller By Head vs Flow Graph, we can say that Ideally we can say that the Head decreases with Disharge or Flow. But Due to Frictional and Recirculation loasses the Head increases with discharge and then start decreasing. The point where the head curve meets the y axis is called shut off head By Efficiency vs Flow graph we can find that efficiency increases to maximum and than decreases with flow. The peak point of the graph with respect to flow by keeping speed and diameter of impeller constant is called best efficiency point(marked as G) Now drop the lines horizontally and vertically from point G to meet the Head Vs Flow line, X and Y axes. The point of intersection on Head vs Flow curve gives the optimal head that can be obtained for maximum efficiency of the pump for corresponding flow. It is marked as A. Optinal Point At point A, for an operating speed and diameter of impeller for which the graphs are drawn, we achieve the maximum head at particular flow at Best efficiency of the pump. At Best efficiecy point the Pump operates smoothly with low noise and vibations.f the values of head or discharge obtained at best efficiency point are altered by keeping one parameter Но constant,then vibrations increase and inturn the life of the pump gets shorten Oy Flo At point B: The point B is with in the regions of Head and Efficiecy graphs, hence this pump can perform for the head level of Hb and Flow of Qb. But the economical aspect of the pump for the point B has to be thought of before taking the Speed of impeller less decision. The values at optimum point are the Designed Head and Designed flow values for this pump. tha r speed of N1 an the above curve. The Pump with Characteristics curve with optimal point close to to point B will yield economically best pump. The Characteristic curve for a speed N1 less than N will give a better best efficiency curve for the same diameter of impeller for the point B. If speed of impeller is reduced the Graphs of Head and efficiency will move towards horizontal axis. Therefore, we assume at speed N1, the point B will get a better efficiency point, so that the pump will operate at least noise and vibration. Hence life pump is maintained