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Terry G Regular
Joined: 04 Mar 1998 Posts: 222
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Posted: Tue Oct 30, 2012 12:21 pm Post subject: Compressed Gas 


Is there a formula that would calculate how many cubic feet of natural gas would be in a gallon size tank at a certain pressure and temperature. For example 1 gallon tank, 2400 psi pressure at a temperature of 60F. 

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buickanddeere Tractor Guru
Joined: 31 May 2003 Posts: 31571 Location: in front of computer
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Posted: Tue Oct 30, 2012 1:56 pm Post subject: Re: Compressed Gas 


Find the btu's of energy per cubic ft then convert to gallons. Figure how many atmospheres of pressure in the tank and multiply. 

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GeoTH,In Tractor Guru
Joined: 05 Aug 2009 Posts: 15358 Location: terre haute
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Posted: Tue Oct 30, 2012 6:17 pm Post subject: Re: Compressed Gas 


Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The before and after volumes and pressures of the fixed amount of gas, where the before and after temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
P1V1=P2V2
Here P1 and V1 represent the original pressure and volume, respectively, and P2 and V2 represent the second pressure and volume.
2400 x 1 = 14.7 x X
X = 163.3 gallons 

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Terry G Regular
Joined: 04 Mar 1998 Posts: 222
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Posted: Tue Oct 30, 2012 8:14 pm Post subject: Re: Compressed Gas 


Thank you for the answers , I finally understand it now. Been thinking on this one for awhile. Should have come here earlier. 

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JMOR Tractor Guru
Joined: 13 Aug 2007 Posts: 21411
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Posted: Wed Oct 31, 2012 7:29 am Post subject: Re: Compressed Gas 


George Marsh wrote:  (quoted from post at 22:17:04 10/30/12) Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas. The before and after volumes and pressures of the fixed amount of gas, where the before and after temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
P1V1=P2V2
Here P1 and V1 represent the original pressure and volume, respectively, and P2 and V2 represent the second pressure and volume.
2400 x 1 = 14.7 x X
X = 163.3 gallons  George, I started to tell him that formula, but thought I would double check my physics book and after I read this (When the pressure of a constant mass of gas is not too great, less than 2 atmospheres, we find that a gas obeys the following relationship: ), I decided not to. That sentence precedes the formula. Do you know why? I don't. The chapter never goes on to address higher pressures & all the problems at end of chapter use pressures below 2 atmospheres. 

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GeoTH,In Tractor Guru
Joined: 05 Aug 2009 Posts: 15358 Location: terre haute
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Posted: Wed Oct 31, 2012 11:44 am Post subject: Re: Compressed Gas 


Jessie,
Not sure exactly what you are asking. The question here was simple, because the temp didn't change. It's a whole different ball game when you compress a gas real fast, isothermal compression, adiabatic compression, monoatomic or diatomic gas. The equations are different for each. I put those books away 8 years ago and never want to open them again.
George 

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JMOR Tractor Guru
Joined: 13 Aug 2007 Posts: 21411
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Posted: Wed Oct 31, 2012 11:49 am Post subject: Re: Compressed Gas 


George Marsh wrote:  (quoted from post at 15:44:01 10/31/12) Jessie,
Not sure exactly what you are asking. The question here was simple, because the temp didn't change. It's a whole different ball game when you compress a gas real fast, isothermal compression, adiabatic compression, monoatomic or diatomic gas. The equations are different for each. I put those books away 8 years ago and never want to open them again.
George  It just looked to me like they were saying that pv/t didn't apply at pressures over 2 atmospheres????? Wondered why & if so, then what applies at higher pressures? 

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