[HBF] Fwd: O2 diffusion

[Hubert Hanghofer]

Liebe Braugemeinde,

Graham Sanders ersucht mich, eine Frage an Euch weiterzuleiten, die -so finde 
ich- interessante Aspekte im Zusammenhang mit offener Gärung aufwirft (-bei 
uns ja weit verbreitet und gerade jetzt wieder diskutiert). Es geht um die 
Diffusionsgeschwindigkeit von Luftsauerstoff in unbelüftete Bierwürze:

----------  Weitergeleitete Nachricht  ----------

Subject: O2 diffusion
Date: Fri, 22 Feb 2002 17:22:47 +1100
From: <craftbrewer at telstra.easymail.com.au>
To: hubert.hanghofer at netbeer.co.at

G'Day Hubert
/
I wonder if you can help me with your digest members. Seems I have a question
 no-one can answer. This is the question I asked other forums. /
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/
My question relates to O2 absorption.
/
If I had a carboy/fermenter of wort, from the boiler with utterly no addition
of O2. And then cool it, say to 10C. What is the rate of O2
absorption thru natural exchange. Now lets generalise and put a
lot of varables to bed. (yes I know it depends on surface area,
currents in the wort and all that stuff). And I know also that most
absorption will occur at the beginning and it slows as it gets
closer to equilibrium.
/
So lets say, ON AVERAGE, For a wort with no O2, at a
temperature of 10C, how long would it take to get to
80% equilibrium with the air O2, and also 100%.
/
Why do I ask. Well I wonder on two accounts. The first is if
one open ferments, and a person does not airate the wort
straight away, I wonder how long they should wait til they can pitch
the yeast. The second reason is I wonder what rate of CO2 evolution
has to occur to override the O2 absorption gradient.
/
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/
As I said, there are a lot of generalisations with the statement, but I want
 an "on average value". If no-one knows the answer, I'll take the formulas
 you need to work it out. /
Thanks mate
/
Shout
Graham Sanders

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