I actually found that same paper on Google, but it doesn't include diameter (let alone area) or flow rate. I'm assuming that some of the other variables in his equations include diameter, pressure or flow rate, but I can't get that specific on every pump I look at. I'm not designing them . . ...
I realize that there are many, many geometries of pumps and volutes so a general or rule-of-thumb type white paper may not exist for what I'm looking for.
Has anyone seen some type of graph or chart that shows how radial thrusts increase with either increasing flow rate or increasing volute...
BigInch,
Yes that is correct and thank you also for your response. My post didn't start as big a discussion as some of the last NPSH posts did. Perhaps that's because I started it at 3:30AM!! Hope I can sleep better tonight after getting answers from you guys.
Katmar, Thanks again for your patience. That makes it clear in terms I can understand. Perhaps with a few more applications I'll gain a better understanding of the equation. Right now it's kind of like velocity cubed. I can use it in an equation, but can't really visualize it!
Katmar,
Okay, I'm feeling really dense here and I appreciate your patience.
My original question was: If a centrifugal pump manufacturer calculates that the NPSH required (NPSHR) is 7 feet, is that always in absolute pressure?
Your answer was: Yes - always absolute.
In your last response...
Katmar, Also, when I'm calculating NPSH available I'm starting with atmospheric pressure above the liquid in my tank. Including atmospheric pressure in the calculation causes my final pressure calculation to be in absolute figures. Is this not correct?
Katmar,
If NPSH is always absolute, then my NPSHA of 20' is already an absolute pressure. Why would I add 15' to it to get 35'? If the absolute pressure inside the pipe is 20' and the absolute pressure outside the pipe is 35', wouldn't air enter the pipe rather than water leave the pipe?
I need some help from one of you pump gurus out there, but I hope this isn't going to start another three month long discussion on NPSH. I'm working with NPSH on a centrifugal pump for the first time in my life, but have read some posts with hundreds of responses. To avoid all those tangential...
