| Topic: |
Science > Physics |
| User: |
"Tom Hubin" |
| Date: |
02 Mar 2004 10:26:46 AM |
| Object: |
Gas Flow vs Pressure, Temperrature, Mix? |
Hello,
I have been searching but cannot find the equations for linear gas flow
in a cylindrical tube.
If I have a cylindrical tube with known diameter and length, known
pressure at each end of the tube, known gas mix, temperature, how do I
calculate the volume flow rate of the gas?
Tom Hubin
thubin@eathlink.net
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| User: "Mark Folsom" |
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| Title: Re: Gas Flow vs Pressure, Temperrature, Mix? |
02 Mar 2004 12:24:47 PM |
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"Tom Hubin" <thubin@earthlink.net> wrote in message
news:4044B5A0.963@earthlink.net...
Hello,
I have been searching but cannot find the equations for linear gas flow
in a cylindrical tube.
If I have a cylindrical tube with known diameter and length, known
pressure at each end of the tube, known gas mix, temperature, how do I
calculate the volume flow rate of the gas?
Calculate the flow rate for laminar flow, then check to see whether the
Reynolds number is near or above the turbulent flow transition. If it is,
maybe you need an anemometer.
Mark Folsom
.
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| User: "Gregory L. Hansen" |
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| Title: Re: Gas Flow vs Pressure, Temperrature, Mix? |
02 Mar 2004 12:13:45 PM |
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In article <4044B5A0.963@earthlink.net>,
Tom Hubin <thubin@earthlink.net> wrote:
Hello,
I have been searching but cannot find the equations for linear gas flow
in a cylindrical tube.
If I have a cylindrical tube with known diameter and length, known
pressure at each end of the tube, known gas mix, temperature, how do I
calculate the volume flow rate of the gas?
Tom Hubin
thubin@eathlink.net
In the viscous flow regime the conductance of a tube is
C = 180 D^4/L P_av liter/sec
D the diameter and L the length in centimeters, P_av the average pressure
in torr.
In the molecular flow regime,
C = 12 D^3/L liter/sec
Independent of pressure.
Throughput is Q=(P1-P2)C.
According to Moore, Davis, and Coplan's _Building Scientific Apparatus_,
in their chapter concerning vacuum systems. Which means roughly
atmospheric pressure and below, no supersonic flows, generally pretty tame
conditions from an engineering standpoint.
--
"Beer is living proof that God loves us and wants us to be happy."
-- Benjamin Franklin
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| User: "Tom Hubin" |
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| Title: Re: Gas Flow vs Pressure, Temperrature, Mix? |
03 Mar 2004 10:01:32 AM |
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Hello Greg,
Thanx for the informative response.
I have been searching the internet for weeks, apparently with the wrong
keywords. A search for "vacuum and conductance" has lead to a wealth of
useful information, including the equations that you show.
I can now say that I am operating in the viscous flow regime between
source tank regulated about 3000 Torr and exit vacuum about 4 Torr.
Tom Hubin
thubin@earthlink.net
*******************************
Gregory L. Hansen wrote:
In article <4044B5A0.963@earthlink.net>,
Tom Hubin <thubin@earthlink.net> wrote:
Hello,
I have been searching but cannot find the equations for linear gas flow
in a cylindrical tube.
If I have a cylindrical tube with known diameter and length, known
pressure at each end of the tube, known gas mix, temperature, how do I
calculate the volume flow rate of the gas?
Tom Hubin
thubin@eathlink.net
In the viscous flow regime the conductance of a tube is
C = 180 D^4/L P_av liter/sec
D the diameter and L the length in centimeters, P_av the average pressure
in torr.
In the molecular flow regime,
C = 12 D^3/L liter/sec
Independent of pressure.
Throughput is Q=(P1-P2)C.
According to Moore, Davis, and Coplan's _Building Scientific Apparatus_,
in their chapter concerning vacuum systems. Which means roughly
atmospheric pressure and below, no supersonic flows, generally pretty tame
conditions from an engineering standpoint.
--
"Beer is living proof that God loves us and wants us to be happy."
-- Benjamin Franklin
.
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| User: "Uncle Al" |
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| Title: Re: Gas Flow vs Pressure, Temperrature, Mix? |
02 Mar 2004 11:30:24 AM |
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Tom Hubin wrote:
Hello,
I have been searching but cannot find the equations for linear gas flow
in a cylindrical tube.
If I have a cylindrical tube with known diameter and length, known
pressure at each end of the tube, known gas mix, temperature, how do I
calculate the volume flow rate of the gas?
Pull some hydrodynamics texts and look up flow through a pipe. As
long as you are in a laminar flow regime it is not overmuch difficult.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "tj Frazir" |
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| Title: Re: Gas Flow vs Pressure, Temperrature, Mix? |
02 Mar 2004 09:57:35 PM |
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nosel chart idiot.
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