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Friday, 30 August 2019

DERIVE THE EXPRESSION FOR MINIMUM STARTING SPEED OF A CENTRIFUGAL PUMP

We were discussing the pumps and basic pumping systemtotal head developed by the centrifugal pumpparts of centrifugal pump and their function, work done by the centrifugal pump on water and heads and efficiencies of a centrifugal pump in our previous post. 

Today we will find out the expression for minimum starting speed of a centrifugal pump. Before deriving the expression for minimum starting speed of a centrifugal pump, we must understand that why we need to find out the expression for minimum starting speed of a centrifugal pump. 

Expression for minimum starting speed of a centrifugal pump 

Centrifugal pump will discharge the water only if the pressure rise in the pump is more than or equal to the manometric head. If the pressure rise in the pump is less than the manometric head, centrifugal pump will not deliver the water. 

While pump impeller will be rotating and water, which will be in contact with pump impeller, will also be rotating and such condition is also termed as forced vortex. 

In case of forced vortex, the centrifugal head or head developed due to pressure rise in the pump impeller will be given by following equation as mentioned here. 


Centrifugal pump will start deliver the water only if 


Therefore above equation derived here provides the expression of minimum speed for starting a centrifugal pump. 

Do you have any suggestions? Please write in comment box.  

Further we will find out, in our next post, Head and efficiency of centrifugal pump. 

Reference: 

Fluid mechanics, By R. K. Bansal 
Image courtesy: Google  

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