1 reply to this topic

[ayyappan]

Hi,

I have a question related to performance of centrifugal pump. If I change the restriction level at out let of centrifugal pump, what will happen to the mass flow or volume flow????


Let me explain it clearly… I have a centrifugal pump running at constant speed, which is connected with a discharge pipe at outlet. The pipe is of 50 mm dia and has some pressure drop value. If I replace the pipe using a small dia of 20 mmm pipe ( increasing the back pressure of pipe) how much the mass flow will get affected????

I have got the constant pump characteristic curve with me when fitted with the pipe of dia 50mm. I have the individual performance curve for both the pipes from CFD. How can I relate the effect of pressure drop of pipe on the mass flow rate of pump???

Any help in this regard will be appreciated.

regards,
Ayyappan.T

[Art Montemayor]

Ayyappan:

Why not just call “the restriction level at out let of centrifugal pump” the centrifugal pump’s discharge line? It is so much simpler and understood immediately since that what everyone else calls it?

The answer to your question (as I understand it) is that the pump’s flow rate will decrease with increased pressure drop in its discharge line. The performance curve on your centrifugal pump should demonstrate this clearly.

The way to understand (and define) the effect that the discharge piping has on the pump’s operation is to do what very few Chemical (& other) engineers do: create a system hydraulic curve and overlay it on the pump’s performance curve. Where the two curves intersect is where the pump will operate and that point defines the operating point as pertains to discharge head and the flow rate. The pump performance curve is usually plotted in Total Developed Head (TDH) versus volumetric flow rate, so you will have to convert the head and the volumetric flow rate to obtain the pressure and the mass flow rate, using the fluid’s density.