# Orifice sizing help

I think my forum name gives it away, I am a home snow maker looking to make a new snow gun and I need a little help from you guys.

Here is my dilemma/situation. I have water flowing at 350 psi, into a pipe that has 100 psi, a differential pressure of 250 psi. I only want .06 gallons per minute of water to enter into the air stream. I was wondering what size orifice would be need to achieve this? thank you all for your help

is this possible?

## Answers and Replies

Andy Resnick
Science Advisor
Education Advisor
Is there a way you could just use a needle valve to control the flow rate?

no it is in such a small area. I need to just figure out what size whole will offer me a flow rate between .06 and .09 at the specs I mentioned before.

Q_Goest
Science Advisor
Homework Helper
Gold Member
Hi snowmaker. I like Andy's idea of adjusting using a valve, but the valve will be very small. Cv will be only 0.0038, which puts it into a very special class of valve.

If you do this with an orifice, you won't get good control, primarily because the discharge coefficient of a hole that small can't be accurately predicted. Let's assume you can cut a http://www.birdprecision.com/PDFs/BDS_sharp_edge_orifices.pdf" [Broken]with a Cd of 0.6, then the hole size has to be 0.016 inches in diameter. So you're talking really tiny stuff.

Also, if you need the velocity after the water goes through the hole to help atomize the water, you won't be able to put the restriction into a tube and then pipe it over to your air line. All that will do is allow the water to trickle out into the air line in big fat drops. What you'll need to do is to have the jet of water mixed directly with the air as it discharges from the restriction.

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Thank you for the help, how big of a hole would be needed if the flow rate was to be around .09 gpm? so you do not think that this has any chance of working at all?

Q_Goest
Science Advisor
Homework Helper
Gold Member
Just ratio the flow to the area. It can be made to work, but consider filtering the water to minimize erosion and potential clogging.

other then filtering what would you suggest to help make it work?

FredGarvin
Science Advisor
Have you checked out fine mist nozzles? There are a lot of manufacturers like Steinen and Danfoss-Hago. They are cheap because they are usually used for oil burning furnaces. I have seen some very small sizes. They are rated at 100 psi so you would have to get a chart for a particular nozzle to see how it flows at 250 psid.

They will have their own built in sintered screen but clogging on nozzles with holes that small is still a problem.

For example:
http://hago.danfoss.com/xxTypex/146069_5TH4449.html