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NPSHR/NPSHA


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#1 MSUEngineer

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Posted 23 January 2008 - 11:34 PM

Anyone give me a straight forward definition of NPSHA and NPSHR. I sort of understand it. Or maybe I am getting bogged down in details, and should just be able to apply the equations instead of understanding what is going on.

#2 owillis28

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Posted 24 January 2008 - 04:00 AM

QUOTE (MSUEngineer @ Jan 23 2008, 05:34 PM) <{POST_SNAPBACK}>
Anyone give me a straight forward definition of NPSHA and NPSHR. I sort of understand it. Or maybe I am getting bogged down in details, and should just be able to apply the equations instead of understanding what is going on.


I asked this same question about a year ago. So sad to know I was doing the same thing this time last year.

Anyway, thought this might help.

click here

owillis

Edited by owillis28, 24 January 2008 - 04:01 AM.


#3 IlPadrino

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Posted 25 January 2008 - 03:27 AM

QUOTE (MSUEngineer @ Jan 23 2008, 06:34 PM) <{POST_SNAPBACK}>
Anyone give me a straight forward definition of NPSHA and NPSHR. I sort of understand it. Or maybe I am getting bogged down in details, and should just be able to apply the equations instead of understanding what is going on.


The PE Notes wiki has something that should be pretty helpful in the pumps section. To access the wiki, see the thread http://engineerboard...?showtopic=4171

#4 MSUEngineer

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Posted 25 January 2008 - 03:22 PM

Thanks. While studying I get bogged down trying to understand what is actually happening. I guess I should just focus on how to apply the equation(s) to a problem, since there are a broad range of questions on the Env exam.

#5 IlPadrino

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Posted 25 January 2008 - 03:29 PM

QUOTE (MSUEngineer @ Jan 25 2008, 10:22 AM) <{POST_SNAPBACK}>
Thanks. While studying I get bogged down trying to understand what is actually happening. I guess I should just focus on how to apply the equation(s) to a problem, since there are a broad range of questions on the Env exam.


It's a delicate balance... "plug and chug" only works if you do enough different problems to be able to apply the pattern. In general, you need to know enough about the process to understand how to apply the equation. The key is knowing when too much is too much. Regarding this subject, I don't think it matters much if you know *how* cavitation occurs, but you do need to know *when* cavitation occurs.

#6 Guest_jartgo_*

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Posted 26 January 2008 - 08:51 PM

QUOTE (MSUEngineer @ Jan 23 2008, 06:34 PM) <{POST_SNAPBACK}>
Anyone give me a straight forward definition of NPSHA and NPSHR. I sort of understand it. Or maybe I am getting bogged down in details, and should just be able to apply the equations instead of understanding what is going on.


I think this concept is fairly important to understand since there are several different aspects from which a question could be formulated. I think the CERM has a reasonably short and adequate explanation with an example problem. I always found it was easiest to draw a schematic when doing these types of problems and "track" the head differences through the schematic. Check out the CERM example.




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