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	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.


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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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