question on air flow rate

[bwilson6561]

If an air tank is filled with 150 psi air. If I want the release the air at a certain rate, say, 20 ml/sec. Is that determined by the size of the orifice? So by varying the size of the orifice with a valve, I can control the air release rate right? If so, can someone tell me the math formula for it?

Thanks

 

[RWF7437]

The manufacturer of the valve can tell you "the math formula" for it. You will also find it useful to use consistent units; not ml/sec and psi.

good luck

 

[katmar]

An orifice is a fixed area device and will give a fixed flow rate for a fixed inlet pressure. As the pressure in your tank decreases your flow rate will decrease too. If you want a steady flow from a varying pressure you will need a more sophisticated solution - a flow meter, a controller and a modulating valve.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[danw2]

There are inexpensive flow regulators called rotameters that have a needle valve to control the flow rate and a floating ball in a vertical tube to indicate the flow rate.

However, as Katmar has pointed out, the flow rate will vary with input pressure for any fixed needle valve position.

However, if your tank pressure is replenished on a periodic basis, for instance, like an iar compressor tank, then install a pressure regulator upstream of the flow regulator.

The regulator brings the tank pressure down from 150 psi to a lower pressure, say 20 psi, which can support your flow rate, and still be high enough to be replenished by the assumed air compressor, before the tank is exhausted.

 

[bwilson6561]

Thanks. I actually thought about incorporating an regulator to the device. However, my goal is to minimize the cost. This will be mass produced so I wonder what's the cheapest regulator available. Precision or flow rate is not important at all. Something that regulate the pressure(up to 150 psi) to 20 psi would be nice.

Mass produced, does anyone know about much cost the added regulator would add?

 

[Eltron]

You can get inexpensive air line regulators from MSC for about $15. However, by varying the pressure you will have to vary the orifice to get the flow rate that you desire.

Dan

http://www.eltronresearch.com