wstahlm80
Member
I am curious as to Problem #117 of the NCEES Civil Sample Questions & Solutions book. The problem provides a "net total dynamic head" and a flow. It asks you to determine which type of single-stage impeller would be the most efficient to use. Using the CERM, I know that I can solve this problem with the following equation:
ns = (n*SQRT(Q)) / (hA^0.75) [EQ: 18.28b]
Where:
ns = what I am solving for to determine the type of impeller
Q = flow (GIVEN as 10cfs)
hA = net total dynamic head (GIVEN as 1200ft)
n = speed in rpm
The answers reference that you should be able to find the solution problem with the HYDRAULIC DESIGN HANDBOOK, MAYS. And viewing the solution, apparently you are able to determine the missing "n" value as 1800 rpm. I do not have the aforementioned reference manual, and cannot seem to find with the CERM how to determine "n."
Can someone help me with this problem? Is there another way to "know" how to determine the rpm of an impeller?
ns = (n*SQRT(Q)) / (hA^0.75) [EQ: 18.28b]
Where:
ns = what I am solving for to determine the type of impeller
Q = flow (GIVEN as 10cfs)
hA = net total dynamic head (GIVEN as 1200ft)
n = speed in rpm
The answers reference that you should be able to find the solution problem with the HYDRAULIC DESIGN HANDBOOK, MAYS. And viewing the solution, apparently you are able to determine the missing "n" value as 1800 rpm. I do not have the aforementioned reference manual, and cannot seem to find with the CERM how to determine "n."
Can someone help me with this problem? Is there another way to "know" how to determine the rpm of an impeller?
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