I've got a 4" duct with a 1" sharp edge metering orifice. Inlet pressure is 18"H2O and outlet is vented to atmospheric pressure. Please help!

If this isn't possible how about: 18"h2o vacuum inlet, and a 4"h2o pressure drop across orifice. thanks, Todd

Oh yeah, It's using clean air and I need cfm output. Thanks again. Todd

Todd,

Go to the following website

www.lmnoeng.com

Go to the section on orifice calculations.

All the formulae necessary for calculating the flow through an orifice are given, so you should be able to do the calculation yourself.

The flow units will not be in cfm, but you should be able to convert to cfm easily.

Note: The site offers you the option of inputting your data into a spreadsheet, but this costs $$$. There is no need as all the equations are specified at the end of the page. There are also plenty of references for flow through orifices.

Niall

Thanks Niall! I've been millin over the equation for a couple days. I can't quite figure how to get the velocity so I can input it into the equation. Was hopin someone here could spell it out for me as to what units of measure they'd be. I'll keep tryin an maybe buy one of the basics books. Thanks again. Anyone else willin to give it a shot? Todd