pressure drops in vacuum systems 1

[pcurry]

Does anyone know how does one go about anticipating the pressure drop due to a complicated nozzle assembly stuck on the end of a vacuum extraction unit hose. the nozzle is annular (donut) in cross section and i can't find any equations for the entry/exit losses into an annular section.
All i need is some idea of the kind of suction i can expect when i stick the prototype nozzle on to my extraction unit.
[sig][/sig]

 

[socrates]

pcurry: I'll look through my books on this and see what I can come up with; however if you or I can't come up with any data on this it would seem to me that you might try using a nozzle of known loss value and then compare vacuum pressures to assess the losses of the unknown nozzle. The other thing you could do is affix the nozzle to a meter of tubing and compare the pressure drop to what you get without the nozzle. That should give you the loss pretty accurately.
Sincerely; Socrates

 

[pcurry]

Thanks for the tip socrates. I think i'll use a flowmeter to get an idea of the total loss coefficient. I don't have any pressure measurement equipment handy. [sig][/sig]