4 replies to this topic

[Raj Mehta]

Dear all,

 

We all know that in case of centrifugal pump, head would remain same irrespective of the liquid being pumped, which means the same pump would pump water or oil or any other fluid to say, 40m head, power being the only thing that changes.

 

Here I present you one case in the attached file wherein, the calculations of differential head are done for water and ethanol separately side by side and the differential head is compared which comes out to be different in this case. 

 

Assumptions: 

 

1. Suction tank is open to atmosphere & discharge tank is pressurized at 2 bar. 

2. Frictional losses are neglected in both suction and discharge for the ease of calculation.

3. pumping is at room temperature. 

 

This differential head which comes out to be different in this particular case (where suction and discharge tank are at different pressures) comes out to be same when both the tanks are at same pressure, as they eventually cancel out while calculating differential head. 

 

Kindly share your views on the same and let me know what possibly could be the reason behind this if everything is correct, or else highlight the mistake. 

Attached Files

•  pump-del head different.pdf   39.57KB   70 downloads

[breizh]

Consider this paper to support your work.

 

Hope this helps

 

Breizh

[fallah]

Dear all,

 

We all know that in case of centrifugal pump, head would remain same irrespective of the liquid being pumped

 

Raj,

 

The above mentioned rule can be valid as long as the rated capacity of the pump remain unchanged. Now with fixing source and destination pressure for two cases, don't you think the pump flowrate and hence pump head are subject to change?

[Raj Mehta]

Mr. fallah, I am sorry, but I am still unable to understand. Can you please try to explain it in a different way. 

 

@ Breizh: Thank you for the document. 

[fallah]

Raj,

 

In fact by keeping the source and destination pressures unchanged you have already changed the pump head/flowrate hence its working point and your calculation also shows this matter...

 

If you want to see the rule validity, you can fix, let say, the suction condition and while using another fluid but with same flowrate allow the discharge head to adust itself accordingly...At this time you will see the pump head is remained unchanged...

 

Then the pump head is remained unchanged in pumping different fluids just for the condition with the same flowrate...

Edited by fallah, 05 July 2013 - 10:39 AM.