Pipe Flow Calculations Forum

Hello Everyone, new to forum here;

I'm looking at the k factor calculations for gradual enlargement and contractions and I see they don't require a Reynolds number input. Are these calculations only valid for "turbulent" flow (i.e. Reynolds No. > 4000)? Can they be used for "laminar" flow (i.e. Reynolds No. < 2500) applications?

Thanks,
Kerry

Also, looking at the K factor calculation for "sudden and gradual contraction" in the "K-Factor=Fittings" calculator:

If I enter the data into the calculator as follows:
Angle = 60 deg.
D1 = 15mm
D2 = 25mm
I get the result: K1 = .22627416; K2 = 1.7459426

If I do the calculation manually per the Flow Theory Page "Flow in valves and fittings":
B = 15/25 = 0.60
K1 = 0.5*(1-B^^2)^^2 = 0.5 (1-[(0.6)*(0.6)])^^2
K1 = 0.5 * 0.4096 = 0.2048

Applying the Gibson Correction Factor for the 60 deg diverging angle:
C = sqrt[sin(Theta/2)] = sqrt[sin(30)]
C = 0.7071
K1 = (0.7071) * (0.2048)
K1 = 0.1448; K2 = 1.1173

In Summary, For the same data input:
Using the calculator: K1 = 0.2263; K2 = 1.7459
Manual calculation: K1 = 0.1448; K2 = 1.1173

Am I doing something wrong? Is there an error in the code or in the theory description?

Thanks,
Kerry

You are right. There is error in calculator which I fixed and I will upload it later.
Thank you!

Thanks for your reply. Please inform us when its been fixed. I appreciate the work that goes into providing these tools, and find them very useful.

Kerry

The coefficient of resistance K calculator is not loading up. The middle box has a red x in upper left corner. Any solutions?


I need the k VALUE for a 48 inch to 54 inch pipeline enlargement fitting flowing 54000gpm (120cfs).

You should have Java runtime enviroment installed.

Hi,
When using the K factor calculator for gradual expansion and contractions i get two results K1 and K2.
Do u use the sum of the two or just one ?

It depends on velocity that you use with K value. If you calculate minor loss as Dp = K rho * v^2 / 2 and use velocity on D1 than you should use K1, and for D2 - K2.