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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


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Contents:
  Mill Gap Setting (Josh Knarr)
  2009 Saint Louis Microfest Homebrew Competition (August Altenbaumer)
  Re: Carbonation saturation (Joe Walts)


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Date: Fri, 6 Mar 2009 08:46:16 -0500
From: Josh Knarr <josh.knarr at gmail.com>
Subject: Mill Gap Setting

What's everyone using for their mill gap setting?

Seems like .039" seems popular (or the default). I am thinking about
building a mill and if there's one clear "winner" of a number, I don't
see any reason to make it adjustable.

Thanks
Josh


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Date: Fri, 6 Mar 2009 08:20:36 -0600
From: August Altenbaumer <afalten at gmail.com>
Subject: 2009 Saint Louis Microfest Homebrew Competition

The Saint Louis Brews are pleased to announce the 2009 Saint Louis
Microfest Homebrew Competition. All entries from this competition
benefit the Lift for Life Gym (http://www.liftforlife.org).

This competition is an AHA/BJCP sanctioned event. Judging is scheduled
for Saturday, April 25, 2009 and will be held in the Elliot Room at
the Schlafly Taproom in Saint Louis, MO. Judging will begin promptly
at 12:00PM (Noon). Those wishing to judge or steward, please contact
me at organizer at stlbrews.org. Winners will be announced during the
Saint Louis Microfest on Saturday, May 2, 2009.

Entries will be accepted until Friday, April 17, 2009. Only beer
entries will be accepted (no meads or ciders). Entry fee is $10 per
entry, and 2 bottles (with no identifying marks) per entry are needed.
Please enter using the appropriate BJCP category
(http://www.bjcp.org/stylecenter.html). The BJCP categories will be
grouped into five larger categories by the organizers (Light Lager,
Dark Lager, Light Ale, Dark Ale, and Microfest Summer Brew).

1st Place in each category wins a $25 Cash Prize. There will also be
prizes awarded to the top ranked beginner (less than two years
brewing).

Judges and stewards can walk-in entries the day of the competition.
Please arrive by 11:00AM to allow time to register and organize the
walk-ins.

Further details and the entry form can found at:
http://www.stlbrews.org/competition/lift_for_life/09Homebrew%20flier_v2.pdf
Please include one entry form with each entry. Also, please attach a
bottle label (rubber band, no tape or glue) to each bottle to avoid
any chance of confusing the organizers.

Any questions about entering or judging can be sent to organizer at stlbrews.org.

Remember that this competition is a benefit for the Lift for Life Gym.
Please enter generously!

Cheers!
Augie Altenbaumer
2009 Saint Louis Microfest Homebrew Competition Organizer


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Date: Fri, 6 Mar 2009 10:58:47 -0600
From: Joe Walts <jwalts at gmail.com>
Subject: Re: Carbonation saturation

I think Fred is on the right track, but his language is confusing.  At
first, I thought he meant the equilibrium pressure at 34 degf and 2.5
volumes of CO2 is 14.7 psig (it's actually about 9.3 psig).  Fred: did
you mean that a tank open to the atmosphere would be 14.7 psia?  Ok,
moving on.

The easiest way to calculate the required CO2 is to assume the
headspace will hold the same mass of CO2 as an equivalent volume of
beer.  In other words, you would eliminate needing to calculate the
beer and headspace CO2 levels separately by treating the entire tank
as a batch of beer.  A volume of CO2 is defined as [volume of
dissolved CO2]/[volume of beer] if the gas were at STP (Standard
Temperature and Pressure, which the ASBC defines as 273.15 K and
101,325 Pa).  The first thing you would need to do is figure out how
much CO2 is already in the tank.  Let's use Fred's example of 900
gallons of beer in a 1,000 gallon (3.79 m^3) tank with a desired
carbonation of 2.5 volumes.  The resulting headspace, used later on,
is 0.38 m^3.  Let's also assume that 15 psi (204,747 Pa) of CO2 was
captured in the beer during fermentation at 68 degf (293.15 K).  Using
the ASBC table or a curve-fit calculation, you can determine that the
initial carbonation would be 1.7 volumes of CO2.  Multiplying by 1,000
gallons will tell you that the CO2 would occupy 1,700 gallons (6.44
m^3) at STP.  You can then use the Ideal Gas Law (pV=nRT -> pV=mRT/MM
where R is the universal gas constant 8.314 Pa*m^3/K/mol and MM is
molar mass of CO2, which equals 44.01 g/mol) to figure out that the
mass of CO2 in the tank = 101325*6.44*44.01/(8.314*273.15) = 12,646 g.
 You can use the same procedure to determine that the final volume of
CO2 at STP = 2.5*1000 = 2,500 gallons (9.46 m^3) and that the final
mass of CO2 in the tank = 101325*9.46*44.01/(8.314*273.15) = 18,576 g.
 The required mass of CO2 to add to the tank = 18576 - 12646 = 5,930
g.  Assuming that none of the added CO2 dissolves right away, and that
the beer had been chilled to 34 degf (274.26 K) before carbonating,
you can use the Ideal Gas Law one more time to figure out that the
initial perssure after adding CO2 = 5930*8.314*274.26/(44.01*0.38) =
102.6 psig.  Figuring out the volume to add is more complicated
because it will depend on the temperature and pressure of the gas
moving through your flowmeter.  If you know what those values are, say
68 degf and 30 psig (308168 Pa), you can use the Ideal Gas Law to
figure out that the required CO2 volume to pass through the flowmeter
= 5930*8.314*274.26/(44.01*308168) = 0.996 m^3 = 996 L.

If you want to be a bigger geek, you can use the Ideal Gas Law to
figure out the initial and final masses of CO2 in the headspace
separately.  Instead of going through all of the calculations here,
you can download a spreadsheet titled "CO2 Volume Calculator" at this
website:

http://jwalts.googlepages.com/math

Interestingly, using the ASBC table results in a greater CO2 mass than
the Ideal Gas Law (for a fixed volume and pressure) at temperatures
below 60ish degf.  That suggests beer can hold more CO2 than an
equivalent volume of empty space at cool temperatures, which I'm very
skeptical of.  I was baffled by this a couple of years ago, but I
couldn't explain it and I forgot about it until now.  Could it be due
to CO2 entering the water's carbonate system?  Is the Ideal Gas Law
invalid for modeling the headspace of a tank?

Joe


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