2 replies to this topic

[Venkat @89]

Why does pump pressure doesn't rise further on running centrifugal pump in discharge valve closed condition, whereas for positive displacement pumps the pressure rises significantly on discharge valve in closed condition, causing severe damage to the connected loops?

Eventhough in both cases liquid flow is not going out.

Where does continuously rotating impeller energy gets converted into?

Kindly guide. Thanks.

Edited by Venkat @89, 20 February 2023 - 10:12 AM.

[SilverShaded]

Maximum head at zero flow and the energy will go into waste heat/higher stream enthalpy.

[latexman]

The centrifugal pump impeller accelerates the liquid to the maximum velocity at the tip/periphery (RPM x radius) of the impeller.  The velocity cannot mechanically exceed this value, so it is "capped".  The diffuser converts this kinetic energy to potential energy (pressure) as per the Bernouilli equation.  Since the kinetic energy is capped, so is the potential energy (pressure).

 

A PD pump keeps packing liquid into the dischagre piping via mechanical displacement until something breaks or a PRD opens.