Velocity Head
Velocity Head
(OP)
I need some direction on velocity head for calculation of centrifugal pump TDH. Is the velocity to be used that measured at the pump discharge nozzle or at the pipe connected to the nozzle (usually larger than the pump nozzle)? Isn't the velocity head at the pump nozzle included by the manufacturer in the pump curve? For example I have a pump with a discharge velocity of 27 fps and its a big difference if this velocity is used for the velocity head calculation instead of the 10 fps which is the velocity in the discharge pipe. Thanks in advance for your comments.





RE: Velocity Head
RE: Velocity Head
Strictly speaking, the velocity head at the pump suction should be taken into account. But the suction nozzle is almost always bigger than the discharge nozzle and because the velocity is proportional to the square of the pipe diameter, and the velocity head is proportional to the square of the velocity, the velocity head at the suction is usually very small compared with that at the discharge. Ignoring the velocity head at the suction makes the sizing slightly conservative and we usually like to hide a bit of extra safety factor where we can.
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Velocity Head
You mentioned:"...the velocity is proportional to the square of the pipe diameter, and the velocity head is proportional to the square of the velocity, the velocity head at the suction is usually very small compared with that at the discharge..."
I am sure in the first part of above mentioned statement you meant:"...the velocity is inversely proportionalto the square of the pipe diameter,.."
RE: Velocity Head
Thanks for the correction e43u8, that is exactly what I should have said.
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Velocity Head
you must get smarter than the software you're using.
RE: Velocity Head
RE: Velocity Head
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Velocity Head
RE: Velocity Head
RE: Velocity Head
RE: Velocity Head
you must get smarter than the software you're using.
RE: Velocity Head
RE: Velocity Head
my understanding is that TDH = algebraic sum of discharge heads - algebraic sum of suction heads
you add the "static heads' and subtract "friction" and "suction lifts heads" based on your specific application.
RE: Velocity Head
http://www.pumped101.com/velocity%20head.pdf