Orifice Size

Is this a homework question?

yes it is.

Thanks.

Do you understand that grams/second is not normally used to describe the flow rate of a gas?

And that the answer depends on many still unknown factors.

I don't see much wrong with describing the flow rate of a gas in grams/second. It's easy enough to convert to normal or standard m³/h, or similar in other units.

I know it can be done. Question is, does the student?

Dunno, maybe he'll come back and tell us

use these till you get the rate you desire

It sure looks like it! The answer is on the graphs you should have.

download engineering power tools, this may help, but you may have to add some constance

http://excelcalculations.blogspot.com/2011/10/gas-orifice-meter-iso-5167.html

Grams per second? It's a trick question.

Yes a trick question, and determining the orifice design tricky as well....good luck

One would be small, the next would be slightly larger, and the third, would be a bit larger yet.

Not sure how to deliver grams/second of compressed nitrogen, not sure that's possible.

Perhaps you should consult your instructor, and ask about those units.

Good luck!

You need to say

1) whether the supply pressure is gauge or absolute

2) downstream pressure

3) upstream temperature

4) is the orifice in the side of a vessel, in a pipe, or what?

The pressure gauge is absolute.

the down flow (pressure) into a container and as the container reaches set pressure

flow stops.

as gas form the container/storage is consumed/utilized at the set volumes (to atmosphere) via the orifice(s) the container/storage is continuously maintained via a pressure regulator form higher source.

the orifice discharges into a chamber (typically atmospheric press.)

That doesn't quite hang together. You say "the down flow (pressure) into a container and as the container reaches set pressure flow stops". Badly worded but I know what you mean. But then you say the upstream pressure is maintained, so you're talking about a steady state condition, and you give specific flow rates. You don't give upstream temp so I'll assume 20°C.

As the downstream/upstream pressure ratio 1/3 is < critical ratio ~ 0.53, flow is sonic. I make dias

2 gm/s 2.43 mm

5 gm/s 3.84 mm

12 gm/s 5.95 mm

Doesn't happen often, but it looks like you got somebody to answer your homework question for you.

I'm still trying to figure out why we are measuring a gas by weight.

How much space does 12 grams of N2 occupy, at let's say 25°C?

Molecular mass of N2 = 28. Molar volume at NTP (1 atm, 0°C) = 22.4 litre/gm.mol. So 12 gm at NTP occupy 12/28*22.4 litre. You didn't specify pressure, but at 1 atm and 25°C, volume = 12/28*22.4*(273 + 25)/273 = 10.48 litre.

I found this, Don't know why you would need to, but here it is :

Use equation n=PV/RT where n is number of moles and R is gas constant. Use R= .8314 L-Atm/mol-K. convert 3 ml to liters(3/1000) and 100C to Kelvin (100+273) and solve for moles.
Convert moles to grams. 1 mol of N2 equals 28 grams

http://wiki.answers.com/Q/Calculate_the_mass_grams_of_N2_gas_required_to_occupy_a_3.0_mL_container_at_100_C_and_0.914_atm_and_explain_how_you_did_it

The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is: PV = NkT, where P is the absolute pressure of the gas; V is the volume; N is the number of particles in the gas; k is Boltzmann's constant relating temperature and energy; and T is the absolute temperature.

http://www.chacha.com/question/what-volume-will-14-grams-of-nitrogen-gas-occupy-at-a-pressure-of-2-atm-and-temperature-of-27-c

http://en.wikipedia.org/wiki/Ideal_gas_law

Thanks guys.

It was sort of a rhetorical question for the OP.