Take the basic non-compressible fluid DP flow calculation:
Q = C’ x sq. root of DP
If DP is 10″ H2O, taking sq. root twice:
sq. rt. of 10 = 3.16″
sq. rt. of 3.16″ = 1.77″
The result would be a false LOW reading.
Now, let’s look at a DP of .9″:
sq. rt. of .9 = .948″
sq. rt. of .948″ = .974″
In this case, the result of taking sq. rt. twice would be a false HIGH reading.
Therefore, correct answer is C) Could be either.
Taking a square root of a fraction (below 1″ or 25.4mm H2O) obviously yields a higher number whereas sq. rt. of whole number yields a lower number.
The same relationship exists in gas and steam calculations because hw is in the numerator portion of the equation.
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