Re: [compost_tea] Re: Air Required was: Air pump selection & 5 gal brewer

From: David Loring <dloring3_at_cox.net>
Date: Thu, 2 Oct 2003 12:38:56 -0700

When you talk about supplying air to microbes in a brewer you have to also =
discuss bubble size. I say this because it is the exchange of Oxygen at th=
e surface of each bubble that determines exchange. That's why aquariums ha=
ve air stones. As bubbles get smaller the ratio of surface area to volume =
of the bubble and thus the exchange of Oxygen increases dramatically. See =
this site for the math http://van.hep.uiuc.edu/van/qa/section/Everything_El=
se/Math/20020124164027.htm

I bring this up now because I just measured the volume of air delivered by =
the 5 gallon KIS machine as best I could. It was at least 1CFM which would=
 sound like enough for around 25 gals of brew. . . but the holes in the wa=
nd at the bottom of the bucket do not create the kind of fizz you get from=
 an aquarium stone or the diffuser in say, my Sotillo 50 gal machine. The =
KIS machine delivers plenty of air for brewing, even up to 90*F, with verm=
icompost and 1oz molasses added. I've checked it several times using an Ox=
ygen meter. But it might not be enough for 25 gals with 5 oz. of molasses =
if one were to scale up with a larger bucket just based on the air flow del=
ivery.

So I'm thinking there are at least three things to consider when designing =
an air pump for an extractor: 1. air flow, 2. air pressure, and 3. what dev=
ice will be used to diffuse the air into the water.

Dave Sotillo 50
  ----- Original Message -----
  From: Lmvine1_at_cs.com
  To: compost_tea_at_yahoogroups.com
  Sent: Thursday, October 02, 2003 6:48 AM
  Subject: [compost_tea] Re: Air Required was: Air pump selection & 5 gal b=
rewer


  In a message dated 10/1/2003 12:31:50 PM Eastern Daylight Time, kirk_at_oreg=
onatural.com writes:

    Jeff's asking how much air is enough is a question I'd
    like to see discussed, as I think it's important.


  Paul Wagner _at_SFI in NY in personal telecon several months ago said 1L/min=
/gallon is air objective (minimum).
  From my experience this seems about right.

  28.3L/min = 1CFM
  So for 5 gallons, need 5L/min or .18CFM.
  For 15 gallons 15L/min or .53CFM
  etc

  I think this is a case where more is better, up to a point of course. Da=
n
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Received on Thu Oct 02 2003 - 17:21:32 EDT

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