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Old 05-07-2013, 01:09 PM   #51
ajdelange
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The 'widget' has evolved appreciably over the years. The last one I looked at was about the size of a ping pong ball with a very small hole at one pole. These are, I assume, filled with nitrogen at atmospheric pressure before being dropped into the can. The can is then filled with beer and a little liquid N2 is squirted in the instant before the lid is clamped on. The can then goes into the pasteurizing tunnel where the heat causes the N2 to evaporate and the pressure becomes quite high so that the beer, at this higher pressure, is forced into the ball. The can is then sent off to the store, put in your refrigerator and eventually taken out. Even though it is now cold the partial pressure of nitrogen in there is a couple of atmospheres. When you open the can the pressure in the head space drops instantly to 1 atm but the pressure in the ball is still much higher than that as it can only bleed off through the tiny hole. In trying to equalize the pressure nitrogen and beer are forced out through the tiny hole. The widget is designed to spin as a result of this jet of beer. This jet of beer agitates the main volume of beer thus causing the CO2 in solution to come out in much the same way it does when the beer is agitated by being forced through a sparkler or restrictor plate.



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Old 02-06-2014, 12:58 AM   #52
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So I'm reviving this old thread. Did anyone ever go forward with the party pig/bladder testing? I'm going to buy a stout faucet and try running it on CO2 alone. It just doesn't make any sense to me to buy a Nitrogen tank and regulator when I won't be running a "nitrogen" beer that often. Just interested how many people have had success with a stout faucet with a low carbed keg running temporarily at a high pressure during serving. This seems to make sense to me and really shouldn't be a big pain in the butt to change the regulator for serving.



 
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Old 05-17-2016, 03:54 PM   #53
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So i'm reviving this once revived old thread because I think we can do much better.
I don't think there is a need, yet, for an experiment as this can all be proven mathematically, and any and all propaganda or articles without mathematical justification can be ignored. In particular, the wikipedia article for partial pressure
https://en.wikipedia.org/wiki/Partial_pressure
has most of the story.
The information needed is:
1) The properties by which nitrogen dissolves in a liquid is known (googlable), and quite negligible unless under extreeeeeeemly high pressures. There is a table on the wiki page for Henry's law that shows this. Co2 has medium solubility, which is why we can use it to make fizz, and nitrogen has very poor solubility.
Pure Speculation: diffusion may speed this up, just like using a stone to aerate your beer, or speed up force carbonation. I suspect this is how small amounts of nitrogen are dissolved into guinness at the factory, as claimed by the propaganda. This type of proprietary knowledge could be verified by an experiment. I liked the pH suggestion in a previous post.
2) The properties by which CO2 dissolve in a liquid are known, and most of us use some type of calculator for this.
3) The properties by which CO2 dissolves in nitrogen (and vice versa) are also known. In particular, co2 readily and easily dissolves in nitrogen
4) From the wiki: "Gases dissolve, diffuse, and react according to their partial pressures, and not according to their concentrations in gas mixtures or liquids." This behavior can be calculated using the formulae in the article.

Put it all together and I think we have the following answer. (Disclaimer: This is still speculation. I'm not a chemist..just a mathematician. I'll try to write this up as theorem and proof if I can find the time. Perhaps even a "how to" so the rest of the world can use their pocket calculators as more than a paper weight.)
1) Nitrogen's function in "beer gas" is solely to provide the added pressure to push through the restrictor plate WITHOUT over-carbonating the beer over time. This functionality can be achieved with any other gas that does not dissolve well, as pointed out by the argon experimenter posts.
2) The same results in pour can be achieved (there is a Brew Your Own article about this) by other means. Namely, crank up the co2 pressure, pour, lower the pressure, vent the keg.
3) it was claimed somewhere in this thread (EDIT: http://www.homebrewtalk.com/showthread.php?t=230229 post #5) that you could a) carbonate with co2, the b) hook up pure nitrogen and leave it with a perfect pour every time. This is a farce. Read the wiki again if you don't believe me. co2 readily dissolves in nitrogen. Thus, the pressure of pure nitrogen in the headspace does nothing to keep the co2 in solution. Only the partial pressure of co2 in the headspace does this. The partial pressure of co2 in solution will move to equilibrium with the head space, and the beer will go flat over time as co2 moves to the headspace. This is why beer gas has co2 in it, at the right partial pressure to maintain carbonation over time.
EDIT: or better yet, the first equation in the wiki shows that (in the headspace) as the volume of nitrogen increases with pints poured, the partial pressure of co2 decreases. Since co2 dissolves easily in nitrogen (this is dalton's law in the wiki), the beer goes flat.

In summary, I propose we develop a mathematical solution based on known chemistry, since none of us are privy to any proprietary information from guinness.

 
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Old 05-17-2016, 06:32 PM   #54
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An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.

 
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Old 05-18-2016, 02:30 AM   #55
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Quote:
Originally Posted by ajdelange View Post
An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.
A marketer and an accountant join them; The accountant says "Hey guys, I think your on to something - we could charge people extra for this"
And the Marketer adds "Yeah, but I think the general public will probably get confused with all you science talk - so let's just say the nitrogen makes smaller bubbles and that's what gives it the creamy texture"

And I think that has now gone full circle back to the beginning of this thread

On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience

 
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Old 05-18-2016, 03:05 AM   #56
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Quote:
Originally Posted by mattd2 View Post
...

On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience
No. You could do it for the initial keg volume, but then as the keg empties, it will take more and more CO2 in the headspace to stay in equilibrium with the carbonation in the beer. So more and more CO2 will diffuse out of the beer, reducing the carbonation level.

Brew on

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Old 05-18-2016, 03:37 AM   #57
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Quote:
Originally Posted by mattd2 View Post
On a serious scientific note though - would it be possible to overcarb the beer on CO2, then pressurise to 30PSI with N2, and if you calculate it correctly end up with the right mix once it all equilibrulisese (word?)... that is if you have enough time/patience
Yes and that is actually how Guiness got to the nitrogen thing. In the 1940's they were selling Guiness in an 11 gal keg with 8 gal beer (not completely fermented) and the head space pressurized to 3.5 atm (absolute) with air. They later replaced the air with pure nitrogen (to discourage bacterial growth according to Carroll) "..which led to the discovery of the dramatic effect of small amounts of dissolved nitrogen gas on head creaminess and durability."

As has been observed, the situation will change as the beer is drawn off but evidently the 3:8 initial ratio of gas to beer is adequate to deliver acceptable product from first to last glass.

Thus you don't actually have to calculate it. Guiness has already done that for you. Carbonate to 1.5 vols then pressurize to 3.5 atm absolute with nitrogen and you should be there.

 
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Old 05-18-2016, 04:41 AM   #58
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Old 05-18-2016, 04:49 AM   #59
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Quote:
Originally Posted by ajdelange View Post
An engineer, a physicist and a mathematician walk into a bar....

The essential facts here are
1) CO2 is much more soluble in water/beer than N2
2) The solubility of CO2 is strongly dependent on temperature; the solubility of N2 isn't.
3) The size of the head in a mixed gas pour depends on the CO2 content
4) The bubbles formed with low Paco2 (partial pressure of CO2) are small
5) If PaN2 is appreciable the bubbles are more stable because the N2 diffuses back into solution more slowly than CO2 does
6)The smaller bubbles give less physical 'prick' on the tongue when they burst.
7)A bubble filled partially with nitrogen gives less carbonic acid 'prick' than a pure CO2 bubble.

The equilibrium equation for the mix of CO2 and Nitrogen as applied to the particular problem of interest can be found in Carroll, T. C. N., The effect of dissolved nitrogen on foam and palate, MBAA TQ, Vol 16, No. 3 1979

It is indeed impossible to mimic the performance of a mixed gas system with nitrogen alone as the beer will go flat (PaCO2 in pure N2 is 0) but it is possible to get a pretty good approximation with pure CO2. One keeps the beer under enough pressure to keep it at 1.2 - 1.5 volumes at the storage temperature then raises the pressure to 20 - 25 psig for serving (i.e. high enough to let the sparkle plate do its job) and then reduces it again at the conclusion of serving. This is clearly not possible if you want your stout 'on tap' but is OK if you are only going to serve it say 1 day a week. I, and several other people have done this. It's not exactly the same but it is pretty close.
actually both CO2 and N2 solubility depends on temperature similarly - with a drop of 2.5-3 from 0C to 40C. Overall CO2 is about 100 times more soluble than N2 (3g/L for CO2 and 0.03 g/L for N2).

http://www.engineeringtoolbox.com/ga...er-d_1148.html

This means that bubbles in your beer are almost entirely CO2 (99% or maybe 97% - depending on gas composition and level of saturation reached).

I doubt that 1% Nitrogen content inside the bubbles contributes to significant reduction of carbonic bite.
I believe Nitrogen contribution in bubbles is irrelevant to the taste - you just need to create small bubbles by applying high pressure and forcing lightly carbed beer through an aperture. The "smooth" taste is simply result of those small bubbles. You can push lightly carbed beer with other gases, or mechanical devices and get the precisely same effect.
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Old 05-18-2016, 05:46 AM   #60
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Quote:
Originally Posted by 55x11 View Post
actually both CO2 and N2 solubility depends on temperature similarly - with a drop of 2.5-3 from 0C to 40C. Overall CO2 is about 100 times more soluble than N2 (3g/L for CO2 and 0.03 g/L for N2).

http://www.engineeringtoolbox.com/ga...er-d_1148.html

This means that bubbles in your beer are almost entirely CO2 (99% or maybe 97% - depending on gas composition and level of saturation reached).

I doubt that 1% Nitrogen content inside the bubbles contributes to significant reduction of carbonic bite.
I believe Nitrogen contribution in bubbles is irrelevant to the taste - you just need to create small bubbles by applying high pressure and forcing lightly carbed beer through an aperture. The "smooth" taste is simply result of those small bubbles. You can push lightly carbed beer with other gases, or mechanical devices and get the precisely same effect.
Since a typical beer gas is 25% CO2 & 75% N2, the N2 partial pressure will be 3X the CO2 partial pressure. Thus you will get about 3 parts N2 to 100 parts CO2. Still not much nitrogen in those bubbles.

Brew on



 
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