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HOMEBREW Digest #5092
HOMEBREW Digest #5092 Mon 13 November 2006
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
Digest Janitor: pbabcock at hbd.org
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Contents:
Calculating BTU ("Mike Sharp")
BTU ("A.J deLange")
SG and CO2 ("A.J deLange")
Hot side aeration (jbryant)
Changing brew system from propane to natural gas ("Chad Stevens")
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Date: Sun, 12 Nov 2006 23:09:37 -0800
From: "Mike Sharp" <rdcpro at hotmail.com>
Subject: Calculating BTU
Jon Judson is considering changing brew system from propane to natural gas,
and asks:
"How do I calculate how many BTUs are required to heat x number gallons of
water from y temperature to z temperature in w amount of time using natural
gas as the fuel?"
A BTU (British Thermal Unit) is the amount of heat needed to raise the
temperature of one pound of water by one degree Fahrenheit.
So, a 200,000 BTU/hr burner should be able to raise 10 gallons of water from
70 to 170 degrees in 2.4 minutes, right? Wrong. You should know that a
rating for a burner in BTU is talking about the BTUs of fuel consumed, not
the heat applied. A lot of the fuel is not completely burned, and a lot of
the heat is lost. Many burners, especially the cheap ones, are very
inefficient. As a result, it's very hard to figure out how fast a burner of
a given BTU will heat water. The real problem is that many burners don't
have a good "turn down ratio", meaning you can't turn them down real low, so
you do want to match your burner to your kettle fairly well.
For highly efficient Natual Gas burners, check out morebeer's natural gas
burners.
http://morebeer.com/browse.html?category_id=1168&keyword=&x=1&y=1
These are of the impingement type, and they work really well. If you look
to see what size burner they sell with a given size system, you'll get a
good idea of how big to go. You can buy this style of burner in a wide
variety of sizes and configurations, though I don't know if B3 can get them
all.
Regards,
Mike Sharp
Kent, WA
[1891.3, 294deg] AR
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Date: Mon, 13 Nov 2006 12:29:02 +0000
From: "A.J deLange" <ajdel at cox.net>
Subject: BTU
Temperature shifts in water are very easily calculated from heat inputs
because 1 BTU is the amount of heat required to raise 1 pound of water 1
degree Fahrenheit. Note that this is an approximation, though a very
good one, as there are several definitions of a BTU and the specific
heat of water does change slightly with temperature. The other piece of
essential information is that a gallon of water weighs about 8.3 pounds
at room temperature (but only about 8 pounds near boiling). Thus the
amount of time (hours) to raise a given volume of water from x to y
degrees is 8.3 times the number of gallons times (y-x) divided by the
heat input in BTU per hour. The tricky part is getting the heat input.
With a pot over a burner a lot of the heat is lost. The best way to get
useful data is to put a measured amount of water into the vessel,
measure the temperature, turn on the heat for a specific length of time,
say 1/4 hour, and measure the temperature rise. The temperature rise
multiplied by the mass of the water (8.3 times the number of gallons)
is the number of BTU the burner transferred to the water in the vessel
in 1/4 hour. Four times that is the BTU per hour value which should be
used in future calculations.
A.J.
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Date: Mon, 13 Nov 2006 13:10:26 +0000
From: "A.J deLange" <ajdel at cox.net>
Subject: SG and CO2
RE: My M.O. when bottling/kegging my beer is to take a S.G. measurement
when the beer goes into the keg or bottling bucket WITHOUT taking a
sample out in a hydrometer jar.
How are you able to do this? If you just drop a hydrometer into the
fermenter or bottling bucket in addition to the frightening risk of
infection the reading would likely be off because of gas bubbles
adhering to the side of the hydrometer in addition to the dissolved CO2
having an effect on the reading. All the published procedures for
measurement of specific gravity go into great detail concerning the
importance of thoroughly degassing the sample for these reasons. Getting
a good hydrometer reading from beer which has been degassed is tough
enough because you never get all the gas out. If doing this in a bucket
how do you get your eye down the the level of the liquid surface for
proper observation of the meniscus? If in a carboy, how do you get the
hydrometer out?
The reason you won't find anything in the literature about this is that
nobody does it. With any amount of gas present hydrometer readings get
thrown off because of CO2 bubbles, pycnometer readings are no good
because gas forms in the pycnometer forcing out beer and as soon as the
ultrasonics hit the beer in a oscillating U-tube density meter gas comes
out throwing their readings off. Furthermore, the density shift would
depend on the amount of dissolved CO2 which would mean an extensive set
of measurements using special pycnometers for many combinations of
temperature and pressure would have to be made in order to construct
tables. To use these tables you would have to know the amount of CO2
dissolved. I suppose you could assume saturation level at whatever
temperature and try spinning the hydrometer to free it from the bubbles
but I still wouldn't know where to send you for.
I suppose we could do a gedenken experiment: Fill a corny keg absolutely
full of water, hold it at 45F and put 9 psi CO2 on it. The tables say
that evenutally it will come to equilibrium at 2 volumes. That means 38
litres of CO2, approximately a mole and a third, have dissolved. This is
59 grams. Thus there are 19L in the keg consisting of 19KG of water and
59 grams of CO2 for a density of (19000 + 59)/19000 = 1.00311 or
specific gravity of 1.00491. That's the amount of increase in density
assuming the volume does not change and is a rough indicator of the
magnitude of the error. Saturated at ambient the dissolved volume would
be about half of this and the resulting SG about 1.0025.
The "proper" way to take an SG reading is to withdraw a sample,
thoroughly degass it, bring it to the hydrometer's working temperature
and lower the hydrometer into the sample. If you are doing this to save
the 50 - 100 mL of beer in the sample, drink the sample or take the lees
from the hydrometer/bottling bucket.
A.J.
------------------------------
Date: Mon, 13 Nov 2006 08:42:47 -0500
From: <jbryant at wrsystems.com>
Subject: Hot side aeration
I was wondering if HSA is a problem when mashing and sparging with water
heated only to around 150 F. I know that when you boil water you
effectively deoxygenate it. When I fill my pot with cold water from the
sink there is plenty of splashing going on, and then I heat that water
to less than boiling. Is this water oxygenated? It seems like brewers
only worry about splashing hot wort, isn't adding oxygenated water to
the grain doing the same thing? Does anyone boil water for mashing and
then let it cool to the right temp?
Jason in Norfolk, VA
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Date: Mon, 13 Nov 2006 18:20:21 -0800
From: "Chad Stevens" <zuvaruvi at cox.net>
Subject: Changing brew system from propane to natural gas
>How do I calculate how many BTUs are required to heat x number gallons of
water from y temperature to z temperature in w amount of time using natural
gas as the fuel?....
Coming from a long line of engineers who adhere to the motto, "When in
doubt, build it stout..." I just bought the biggest f'n burner I could find
and ran really big pipe over a very short run from the meter, thus ensuring
I could melt stainless if left unattended. Unfortunately, this approach has
lead to vast underutilization of the 200,000 BTU burner I purchased, and the
flame tends to carbon the bottom of my brew kettle (indicating incomplete
combustion). Next time around, I think I'd go with a 100,000 BTU burner for
5 to 15 gallon batches.
This doesn't answer your question, but I'm verbose, self righteous, and
always happy to throw in my $0.02 even when the resultant dialog is
tangential to the point at hand.
:o)
Chad Stevens
QUAFF
San Diego
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End of HOMEBREW Digest #5092, 11/13/06
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