Help! Darcy's equation for Resistance Coefficient

[kevin42036]

Hi I need to find the coefficient of resistance K for a reducer with inlet nominal size 32 and outlet nominal size 30. The wall thickness is 1.5 inches. Would I use the equation K = 0.5(1-(dnom/d1)^2)^2 ? If so, which nominal size would i put in for dnom and what value would I plug in for d1? Would I do 0.5(1-(32/27.16)^2)^2 ?

Or if anybody can provide me with some examples of similar problems to look at? I have not been able to find any

Thanks!
K.C

 

[katmar]

You need to work with the inlet and outlet actual inside diameters. The nominal sizes are not important in calculations. Tablulated data often refers to nominal sizes, but it is the actual dimensions that determine the pressure drop. You also need to know the angle of taper.

The usual reference for this sort of work is the Crane TP 410 manual, but you should find the equations in almost any fluid mechanics book.

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