Physics (or Google) experts ...

tc · 10-31-2009, 11:06 PM

I know there is a critical pressure where CO2 will condense into a liquid, and you can store a helluva lot more than a non-condensing gas like air or nitrogen.

How much more?

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Just Learning · 11-01-2009, 01:39 AM

why do you ask-?? but you can store more gas than a liquid- you can compress a gas where you can compress a liquid --, i compress gas daily--steam

***fustercluck*** · 11-01-2009, 06:58 AM

I only compress gas long enough to enhance the release...

tc · 11-01-2009, 07:13 AM

One of the guys in COTTORA must not have taken physics/chemistry and doesn't believe me.

I can't find the graph/info I'm looking for.

SC4Runner · 11-01-2009, 09:33 AM

I'm 90% sure you can solve it by using the ideal gas law for both CO2 and "air". Two states, one at a pressurized state (whatever the pressure inside the bottle is for CO2) and then estimate the volume increase to atmospheric pressure. It will be way way larger, I am pretty sure the volume expansion will be somewhere in the 1,000 times expansion in volume...(for liquid to gas, rather than just pressurized gas to gas).

SC4Runner · 11-01-2009, 09:36 AM

Just found this for water:

Question - I am 84 wondering how much a cubic inch of water will
expand when turned into steam that is saturated how much does it expand
when superheated

Answer - "The so-called "ideal gas law": P*V = n * R * T where P is the pressure in
atmospheres, V is the volume in liters, n is the number of mols which is
equal to gm / MW (where gm is the weight of the amount of gas and MW is the
molecular weight (for water MW = 18), and T is the temperature in kelvins:
T = C + 273.15 where C is the temperature in degrees Celsius, and R = a
constant = 0.082 liter * atm / mol * kelvins. For water at its boiling
point, (100 C = 373.15 kelvins), P = 1 atm; choose
n = 1 so that gm = 18 and MW = 18, and T = 373.15 and R = 0.0825 l * atm /
mol * kelvins, so:
V = 0.082 * 373.15 / 1(atm) = 30.6 liters. This is a large expansion because
18 gm water = 18 cm^3 =
0.018 liters that is an increase in volume of about 1700 times!"

**waskillywabbit** · 11-01-2009, 09:57 AM

Some good CO2 info on this page talking about phase diagrams etc.

http://www.science.uwaterloo.ca/~cch...phasesdgm.html

tc · 11-01-2009, 03:44 PM

Yeah, I found that one, and it's good for showing that it will condense to liquid at certain pressures/temperatures, but doesn't relate that to volume/density

SC4Runner · 11-01-2009, 06:46 PM

Fine I did the calculations for you.

I am pretty sure these are correct. If not, I hope someone else steps in.

For a 10 gallon container (I know large).
Co2 @ 853 psi, Liquid state to Co2 @ 1atm = 581 gallons of vapor

Air @ 200 psi to 1 atm = 136 gallons of air.

So, with Co2, you roughly get 445 more gallons of useful "air" per 10 gallons.

However, I believe you can only fill a Co2 tank to a certain amount...~40-50% full, right? If thats the case then it will go down further. Also temperature does play a roll but I held that constant, which may increase error.

These will slightly decrease since putting into a slightly compressed state of air pressure.

SC4Runner · 11-02-2009, 07:29 AM

Ok I just read the post on COTORRA and he might be right.... Nitrogen, if compressed to 3000 psi would yield greater volume than Co2 at ~1000 psi.

VSU_4runnin · 11-02-2009, 07:49 AM

as far as condensing co2 into a liquid, it not only involves pressure, but a specific temperature has to be maintained as well. when a gaseous compound de-compresses it cools. When it is compressed, especially at high pressures it heats. If this temperature to pressure ratio is not maintained, then you run the risk of creating a solid (dry ice) or a super critical fluid (properties of both liquids and gasses) however, it can only be maintained at a liquid state at or above 5atm.
Liquid density (at -20 °C (or -4 °F) and 19.7 bar) : 1032 kg/m3
Liquid/gas equivalent (1.013 bar and 15 °C (per kg of solid)) : 845 vol/vol
Gas density (1.013 bar at sublimation point) : 2.814 kg/m3
Gas density (1.013 bar and 15 °C (59 °F)) : 1.87 kg/m3

this was the best diagram I could find for you.

Bar to psi converter
Kelvin to Fahrenheit converter

mastacox · 11-02-2009, 08:17 AM

You can't use ideal gas law to figure out when CO2 will liquify. What you're looking for is thermophysical properties of CO2; I use the NIST website to find thermophysical properties of fluids all the time.

NIST: Thermophysical properties of fluid systems

Isothermal properties for Carbon Dioxide

I took the liberty of attaching a few charts from the site, one is for CO2 at 0 degrees F, one at 75 degrees F, and one at 120 degrees F. Notice at 120 degrees, CO2 doesn't actually liquify, it transitions into a supercritical gas.

At 75 degrees F, CO2 transitions to liquid at 910 psi, and the density ratio between the gas at 910 psi vs. liquid at 910 psi is 3.1 (the liquid is 3.1 times denser than the gas).

At 0 degrees F, CO2 transitions to liquid at 305 psi the density ratio between the gas at 305 psi vs. liquid at 305 psi is 18.7 (the liquid is 18.7 times denser than the gas).

mastacox · 11-02-2009, 08:23 AM

Quote:

Originally Posted by SC4Runner

Ok I just read the post on COTORRA and he might be right.... Nitrogen, if compressed to 3000 psi would yield greater volume than Co2 at ~1000 psi.

Nope, not even close. Nitrogen at 3000psia and 75 F is about 13 lbm/ft^3. CO2 at 1000psia and 75F is a liquid, and 47 lbm/ft^3. Also an interesting is the fact that upping the CO2 pressure to 3000psia doesn't net you much more, only up to 57 lbm/ft^3. So a 300% increase in pressure only increases density by 21%. At 0 degrees F the difference is even more pronounced, N2 at 3000psia has a density of 16.7 lbm/ft^3, but CO2 at 1000psia has a density of 65 lbm/ft^3.

Thermophysical properties of CO2

Thermophysical properties of N2

VSU_4runnin · 11-02-2009, 08:53 AM

I yeld to the higher knowledge.. haha
why can the ideal gas laws not be used? beccause there is no assurance of a homogenous mixture?
and i got this
Liquid density (at -20 °C (or -4 °F) and 19.7 bar) : 1032 kg/m3
Liquid/gas equivalent (1.013 bar and 15 °C (per kg of solid)) : 845 vol/vol
Gas density (1.013 bar at sublimation point) : 2.814 kg/m3
Gas density (1.013 bar and 15 °C (59 °F)) : 1.87 kg/m3
from one of my engineering professors who is a division rep. for air liquide so i figured that the densities at temp. were correct

mastacox · 11-02-2009, 08:55 AM

Think of it this way-

For CO2 at 1000psia, it's density compared to CO2 at 14.7psia is 431:1.

For N2 at 3000psia, it's density compared to N2 at 14.7psia is 197:1.

So in this light, you can basically carry more than twice as much CO2 than N2 in a tank, and that's with CO2 at 1/3 the pressure (= safer) ...and if the CO2 was at 3000psia, it's expansion ratio would be about 523:1.

mastacox · 11-02-2009, 09:01 AM

Quote:

Originally Posted by VSU_4runnin

I yeld to the higher knowledge.. haha
why can the ideal gas laws not be used? beccause there is no assurance of a homogenous mixture?

It's because CO2 goes through a phase tansition to liquid (and N2 technically goes through one to supercritical gas as well). Besides, using the tables of data is more accurate because it takes into account the changes in gas properties as a function of pressure and temperature.

VSU_4runnin · 11-02-2009, 10:14 AM

ok, that makes sence.

SC4Runner · 11-02-2009, 11:19 AM

Ok yes, I'm an idiot. You need to use the phase change model. I got, for at 70F, from 1000 psi to 1atm

Co2: 416:1 expansion
N2: 189:1 expansion

Co2 = Mo' bettah!

mastacox · 11-02-2009, 11:31 AM

Quote:

Originally Posted by SC4Runner

Ok yes, I'm an idiot. You need to use the phase change model. I got, for at 70F, from 1000 psi to 1atm

Co2: 416:1 expansion
N2: 189:1 expansion

Co2 = Mo' bettah!

Those numbers are also very close to the NIST data, so you definitely got it right the second time around (except that your expansion ratio for N2 is probably from 3000psi, because the expansion ratio of N2 gas from 1000psi is only 69.2:1).

Note that the N2 expansion ratio is basically just a ratio of its pressure WRT atm (e.g. 1000psi/14.7psi = 68.0), because no phase transition is involved.

11-01-2009, 06:58 AM	#3 (permalink)
*fustercluck* Sponsoring Member Join Date: Sep 2004 Location: right here. Posts: 7,061	I only compress gas long enough to enhance the release... __________________ War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse. The person who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself. John Stuart Mill English economist & philosopher (1806 - 1873)

11-01-2009, 07:13 AM	#4 (permalink)
tc Contributing Member Join Date: Nov 2005 Location: Longmont, CO Posts: 8,377	One of the guys in COTTORA must not have taken physics/chemistry and doesn't believe me. I can't find the graph/info I'm looking for. __________________ Check out www.coTTORA.org to hook up with great Toyota 'wheelin' folks! Current - 93 4Runner: 3VZ 33"x10.50" no lift ARB F/R 96 Impala SS: My own personal cop car Previous - 89 2WD Pickup 22R, Fabtech "Ivan Dan" lift, 31x10.50, IASCA World Finals 4th Place Stop with the mods and get on the trail! Pix at www.4wheelingoh.shutterfly.com/action

11-01-2009, 09:33 AM	#5 (permalink)
SC4Runner Contributing Member Join Date: Apr 2004 Location: 5th Gen San Diegan, California Posts: 5,895	I'm 90% sure you can solve it by using the ideal gas law for both CO2 and "air". Two states, one at a pressurized state (whatever the pressure inside the bottle is for CO2) and then estimate the volume increase to atmospheric pressure. It will be way way larger, I am pretty sure the volume expansion will be somewhere in the 1,000 times expansion in volume...(for liquid to gas, rather than just pressurized gas to gas). __________________ 1996 4x4 3.4L 4Runner on 35's - 6" of lift, MTR's, E-locked, ARB Tacoma Bumper, Sliders and a cut off tail pipe. 1966 FJ40 - SOA with stock springs, stock 1F motor, and a smelly tailpipe.

11-01-2009, 09:36 AM	#6 (permalink)
SC4Runner Contributing Member Join Date: Apr 2004 Location: 5th Gen San Diegan, California Posts: 5,895	Just found this for water: Question - I am 84 wondering how much a cubic inch of water will expand when turned into steam that is saturated how much does it expand when superheated Answer - "The so-called "ideal gas law": PV = n R * T where P is the pressure in atmospheres, V is the volume in liters, n is the number of mols which is equal to gm / MW (where gm is the weight of the amount of gas and MW is the molecular weight (for water MW = 18), and T is the temperature in kelvins: T = C + 273.15 where C is the temperature in degrees Celsius, and R = a constant = 0.082 liter * atm / mol * kelvins. For water at its boiling point, (100 C = 373.15 kelvins), P = 1 atm; choose n = 1 so that gm = 18 and MW = 18, and T = 373.15 and R = 0.0825 l * atm / mol * kelvins, so: V = 0.082 * 373.15 / 1(atm) = 30.6 liters. This is a large expansion because 18 gm water = 18 cm^3 = 0.018 liters that is an increase in volume of about 1700 times!" __________________ 1996 4x4 3.4L 4Runner on 35's - 6" of lift, MTR's, E-locked, ARB Tacoma Bumper, Sliders and a cut off tail pipe. 1966 FJ40 - SOA with stock springs, stock 1F motor, and a smelly tailpipe.

11-01-2009, 09:57 AM	#7 (permalink)
waskillywabbit Super Moderator-Sponsoring Member Staff Join Date: Jul 2003 Location: Tuscaloosa, AL Posts: 14,561	Some good CO2 info on this page talking about phase diagrams etc. http://www.science.uwaterloo.ca/~cch...phasesdgm.html __________________ WabFab Off-Road, LLC MySpace Twitter Facebook 7th Annual South East 4Runner Jamboree, 2010 The toughest part of a Jeep is the chick driving it. WabFab Off-Road 4th Anniversary Sale

11-01-2009, 01:39 AM	#2 (permalink)
Just Learning Registered User Join Date: Oct 2006 Location: Evans Colorado Posts: 696	why do you ask-?? but you can store more gas than a liquid- you can compress a gas where you can compress a liquid --, i compress gas daily--steam

11-01-2009, 03:44 PM	#8 (permalink)
tc Contributing Member Join Date: Nov 2005 Location: Longmont, CO Posts: 8,377	Yeah, I found that one, and it's good for showing that it will condense to liquid at certain pressures/temperatures, but doesn't relate that to volume/density __________________ Check out www.coTTORA.org to hook up with great Toyota 'wheelin' folks! Current - 93 4Runner: 3VZ 33"x10.50" no lift ARB F/R 96 Impala SS: My own personal cop car Previous - 89 2WD Pickup 22R, Fabtech "Ivan Dan" lift, 31x10.50, IASCA World Finals 4th Place Stop with the mods and get on the trail! Pix at www.4wheelingoh.shutterfly.com/action

11-01-2009, 06:46 PM	#9 (permalink)
SC4Runner Contributing Member Join Date: Apr 2004 Location: 5th Gen San Diegan, California Posts: 5,895	Fine I did the calculations for you. I am pretty sure these are correct. If not, I hope someone else steps in. For a 10 gallon container (I know large). Co2 @ 853 psi, Liquid state to Co2 @ 1atm = 581 gallons of vapor Air @ 200 psi to 1 atm = 136 gallons of air. So, with Co2, you roughly get 445 more gallons of useful "air" per 10 gallons. However, I believe you can only fill a Co2 tank to a certain amount...~40-50% full, right? If thats the case then it will go down further. Also temperature does play a roll but I held that constant, which may increase error. These will slightly decrease since putting into a slightly compressed state of air pressure. __________________ 1996 4x4 3.4L 4Runner on 35's - 6" of lift, MTR's, E-locked, ARB Tacoma Bumper, Sliders and a cut off tail pipe. 1966 FJ40 - SOA with stock springs, stock 1F motor, and a smelly tailpipe.

11-02-2009, 07:29 AM	#10 (permalink)
SC4Runner Contributing Member Join Date: Apr 2004 Location: 5th Gen San Diegan, California Posts: 5,895	Ok I just read the post on COTORRA and he might be right.... Nitrogen, if compressed to 3000 psi would yield greater volume than Co2 at ~1000 psi. __________________ 1996 4x4 3.4L 4Runner on 35's - 6" of lift, MTR's, E-locked, ARB Tacoma Bumper, Sliders and a cut off tail pipe. 1966 FJ40 - SOA with stock springs, stock 1F motor, and a smelly tailpipe.

11-02-2009, 07:49 AM	#11 (permalink)
VSU_4runnin Registered User Join Date: Oct 2008 Location: South Georgia Posts: 657	as far as condensing co2 into a liquid, it not only involves pressure, but a specific temperature has to be maintained as well. when a gaseous compound de-compresses it cools. When it is compressed, especially at high pressures it heats. If this temperature to pressure ratio is not maintained, then you run the risk of creating a solid (dry ice) or a super critical fluid (properties of both liquids and gasses) however, it can only be maintained at a liquid state at or above 5atm. Liquid density (at -20 °C (or -4 °F) and 19.7 bar) : 1032 kg/m3 Liquid/gas equivalent (1.013 bar and 15 °C (per kg of solid)) : 845 vol/vol Gas density (1.013 bar at sublimation point) : 2.814 kg/m3 Gas density (1.013 bar and 15 °C (59 °F)) : 1.87 kg/m3 this was the best diagram I could find for you. Bar to psi converter Kelvin to Fahrenheit converter __________________ 1998 Toyota 4Runner: 33" BFG A/T T/A: KO 2.5" Lift CB Radio Brush Guard Yakima roof rack manikin head (Viola), and more to come! Clicky For Picky Buildup GATTORA KJ4HVQ Skywarn Ga 208 ΦΣK DAMN PROUD! Last edited by VSU_4runnin; 11-02-2009 at 08:10 AM.

11-02-2009, 08:17 AM	#12 (permalink)
mastacox Contributing Member Join Date: Dec 2003 Location: Los Alamos, NM Posts: 2,655	You can't use ideal gas law to figure out when CO2 will liquify. What you're looking for is thermophysical properties of CO2; I use the NIST website to find thermophysical properties of fluids all the time. NIST: Thermophysical properties of fluid systems Isothermal properties for Carbon Dioxide I took the liberty of attaching a few charts from the site, one is for CO2 at 0 degrees F, one at 75 degrees F, and one at 120 degrees F. Notice at 120 degrees, CO2 doesn't actually liquify, it transitions into a supercritical gas. At 75 degrees F, CO2 transitions to liquid at 910 psi, and the density ratio between the gas at 910 psi vs. liquid at 910 psi is 3.1 (the liquid is 3.1 times denser than the gas). At 0 degrees F, CO2 transitions to liquid at 305 psi the density ratio between the gas at 305 psi vs. liquid at 305 psi is 18.7 (the liquid is 18.7 times denser than the gas). Attached Thumbnails __________________ Brian 1998 4Runner SR5 Last edited by mastacox; 11-02-2009 at 09:27 AM.

11-02-2009, 08:53 AM	#14 (permalink)
VSU_4runnin Registered User Join Date: Oct 2008 Location: South Georgia Posts: 657	I yeld to the higher knowledge.. haha why can the ideal gas laws not be used? beccause there is no assurance of a homogenous mixture? and i got this Liquid density (at -20 °C (or -4 °F) and 19.7 bar) : 1032 kg/m3 Liquid/gas equivalent (1.013 bar and 15 °C (per kg of solid)) : 845 vol/vol Gas density (1.013 bar at sublimation point) : 2.814 kg/m3 Gas density (1.013 bar and 15 °C (59 °F)) : 1.87 kg/m3 from one of my engineering professors who is a division rep. for air liquide so i figured that the densities at temp. were correct __________________ 1998 Toyota 4Runner: 33" BFG A/T T/A: KO 2.5" Lift CB Radio Brush Guard Yakima roof rack manikin head (Viola), and more to come! Clicky For Picky Buildup GATTORA KJ4HVQ Skywarn Ga 208 ΦΣK DAMN PROUD!

11-02-2009, 08:55 AM	#15 (permalink)
mastacox Contributing Member Join Date: Dec 2003 Location: Los Alamos, NM Posts: 2,655	Think of it this way- For CO2 at 1000psia, it's density compared to CO2 at 14.7psia is 431:1. For N2 at 3000psia, it's density compared to N2 at 14.7psia is 197:1. So in this light, you can basically carry more than twice as much CO2 than N2 in a tank, and that's with CO2 at 1/3 the pressure (= safer) ...and if the CO2 was at 3000psia, it's expansion ratio would be about 523:1. __________________ Brian 1998 4Runner SR5

11-02-2009, 10:14 AM	#17 (permalink)
VSU_4runnin Registered User Join Date: Oct 2008 Location: South Georgia Posts: 657	ok, that makes sence. __________________ 1998 Toyota 4Runner: 33" BFG A/T T/A: KO 2.5" Lift CB Radio Brush Guard Yakima roof rack manikin head (Viola), and more to come! Clicky For Picky Buildup GATTORA KJ4HVQ Skywarn Ga 208 ΦΣK DAMN PROUD!

11-02-2009, 11:19 AM	#18 (permalink)
SC4Runner Contributing Member Join Date: Apr 2004 Location: 5th Gen San Diegan, California Posts: 5,895	Ok yes, I'm an idiot. You need to use the phase change model. I got, for at 70F, from 1000 psi to 1atm Co2: 416:1 expansion N2: 189:1 expansion Co2 = Mo' bettah! __________________ 1996 4x4 3.4L 4Runner on 35's - 6" of lift, MTR's, E-locked, ARB Tacoma Bumper, Sliders and a cut off tail pipe. 1966 FJ40 - SOA with stock springs, stock 1F motor, and a smelly tailpipe.

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