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Old Mar 2nd 2012, 01:59 PM   #1
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Calculating the volumetric rate of flow for pressurized gas out of a circular nozzle.

Hello! My physics knowledge is pretty rusty, but I am trying to solve an engineering problem, and I really need some help. I am trying to figure out the volumetric rate of flow for compressed nitrogen gas being emitted from a circular nozzle.

I have some data provided by a vendor with varying nozzle sizes and pressures that I'm trying to match, but I'm having difficulty getting the math to work out such that I can derive the values given. Unfortunately, I don't have much information beyond that, but if I have the correct equations, I'm hoping that I should be able to figure out any relevant constants or conditions like temperature, etc.

I've looked in a lot of different directions, but I'm not sure I'm doing the right thing. Firstly, I looked at Bernoulli's equation adjusted for compressible flow, but I'm not sure of the initial density or the ending density. I imagine the ending density can be computed for Standard Temperature and Pressure using the ideal gas laws, but if I do the same for the starting density, I run into the same problem.

I then looked into the choked flow flow equations, but I run into a similar problem where I don't have the starting density. I tried deriving it using the ideal gas law and assuming the end density was STP, but I didn't get anywhere near the vendor's data.

I apologize if I am forgetting anything important. If it helps, some example data is as follows: The Nitrogen Gas is at 5 Bar, and a nozzle has a radius of 1". The flow in Ft^3/hour is apparently 290, but I'm not sure how to calculate that.

Thanks!
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Old Mar 6th 2012, 05:51 PM   #2
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[quote=Sharktopus;18316]Hello! My physics knowledge is pretty rusty, but I am trying to solve an engineering problem, and I really need some help. I am trying to figure out the volumetric rate of flow for compressed nitrogen gas being emitted from a circular nozzle.

I have some data provided by a vendor with varying nozzle sizes and pressures that I'm trying to match, but I'm having difficulty getting the math to work out such that I can derive the values given. Unfortunately, I don't have much information beyond that, but if I have the correct equations, I'm hoping that I should be able to figure out any relevant constants or conditions like temperature, etc.

I've looked in a lot of different directions, but I'm not sure I'm doing the right thing. Firstly, I looked at Bernoulli's equation adjusted for compressible flow, but I'm not sure of the initial density or the ending density. I imagine the ending density can be computed for Standard Temperature and Pressure using the ideal gas laws, but if I do the same for the starting density, I run into the same problem.

I then looked into the choked flow flow equations, but I run into a similar problem where I don't have the starting density. I tried deriving it using the ideal gas law and assuming the end density was STP, but I didn't get anywhere near the vendor's data.

I apologize if I am forgetting anything important. If it helps, some example data is as follows: The Nitrogen Gas is at 5 Bar, and a nozzle has a radius of 1". The flow in Ft^3/hour is apparently 290, but I'm not sure how to calculate that.

Thanks![/quote

Google -gas flow thru nozzles ( critical flow--sonic velocity) Engineering Tool Box)
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Old Mar 7th 2012, 05:14 PM   #3
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choked gas flow

I have located an equation in US eng units.Chemical Engineering Thermodynamics,Dodge (1944)

w = C A( (gk(p1) d1(2/k+1)^ k+1/k-1 ))^1/2
w =lbper sec,C discharge coeff. (.95 for nozzle flow)
A = nozzle area ft^2
p1 = upstream pressure lb/sqft absolute
k= Cp/Cv =1.4 for nitrogen
g = 32.2 ft/sec^2
d1 = density at upstream T deg R F +460 and pressure lb/sqft abs
you can use the ideal gas law to find lb per cuft

Post your inputs.I will give my calculations Downstream conditions are not revelant

Last edited by bjhopper; Mar 7th 2012 at 05:17 PM. Reason: correct unit error
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Old Mar 12th 2012, 11:58 PM   #4
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calculating, circular, flow, gas, nozzle, pressurized, rate, volumetric



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