Expression for pressure drop

[student]

I have a simple pressure drop question. I am conducting a simple experiment to measure pressure drop across various pipes and fittings. I am having trouble verifying the expressions that I have found concerning "sudden expansion" and "sudden contractions" fittings. I need an equation that will allow me to calculate the pressure drop through these fittings and maybe a reference. Pipe specs..(1) Brass, 1/2 schedule 40, 15 feet and (2) steel, 1/2 schedule 40. Sudden expansion 1/2 to 1 in. Sudden contraction 1 to 1/2 in. The fluid that is flowing through the pipes is compressed air

[admin]

For head losses over local resistances you can use following text:
http://www.pipeflowcalculations.com/pip ... length.htm
Now, to calculate resistance coefficient for sudden contraction and enlargement, you can use momentum with Bernoulli equations, and it is for contraction:
K1=0.5*(1-(d1/d2)^2)
and for enlargement:
K1=(1-(d1/d2)^2)^2

or you can use calculator for local resistance coefficient:
http://www.pipeflowcalculations.com/res ... /index.htm