Pump NPSH: Velocity Head vs Acceleration Head

[processguy89]

Hi guys,

I think I've been confusing myself using these two terms interchangeably (velocity head and acceleration head) in my NPSH calculations since the definitions are so similar.

I always thought acceleration head was a loss and only noticeable for a positive displacement pump. Therefore acceleration head should be SUBTRACTED in the NPSHa formula.

However, I saw this reference source for NPSH calculations (See page 3):

http://www.pumpschool.com/applications/NPSH.pdf

They are ADDING the velocity head (Hv) term in the NPSH calculation instead.

So I'm a little confused now, can someone clarify?

Thanks!