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HOMEBREW Digest #5508
HOMEBREW Digest #5508 Thu 19 February 2009
FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
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Contents:
Re: Heat calculations and thermal mass (Matt)
Lansing Water ("A.J deLange")
Thermal Mass of Mash Tuns ("A.J deLange")
Re: Thermal Mass (Joe Walts)
Re: Heat calculations and thermal mass (Calvin Perilloux)
Boston Homebrew Competition - Call for Judges (Eric Wooten)
Thermal Mass (Kevin Elsken)
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Date: Wed, 18 Feb 2009 20:42:02 -0800 (PST)
From: Matt <baumssl27 at yahoo.com>
Subject: Re: Heat calculations and thermal mass
> I am wondering what is the cause of this discrepancy.
Slaking heat! The hydration of malt involves chemical
reactions that release significant amounts of heat. Thus
it *appears* to require less heat than expected to bring
the cold mash tun up to mash temp.
For not very detailed details, take a look at Malting and
Brewing Science by Briggs and Shanks on google books, and
search for "slaking heat." A 5F temp shift is indicated
under pretty standard conditions.
For single infusion mashes at 150F at 1.5 qt/lb in my
system, the two effects cancel well enough that I routinely
ignore them both and hit mash temps to within 1F (and I
don't measure my strike water volume with much care, either).
Unfortunately it's not always so easy. Mash tun thermal
mass and slaking heat have different effects under different
mash conditions and a single "fudge factor" can't account
for both of them at once. More calculation complexity is
needed to account for them well. Further, theoretical values
are not easy to come by and at least for me the numbers in
the above reference don't work well (half works much better).
This is not surprising given the complex nature of the
reaction, different malt grinds, many variables, etc.
I think one would have to be very lucky to arrive at a formula
to predict mash temps to within, say, 1F on a given system
without some fairly thorough observations of different mashes
on that system.
Matt
------------------------------
Date: Thu, 19 Feb 2009 08:08:02 -0500
From: "A.J deLange" <ajdel at cox.net>
Subject: Lansing Water
The water in question has Ca: 20, Mg: 9.7, Na: 44, SO4: 70; Cl: 46,
HCO3 42.1 all assumed to be mg/L which is a reasonable assumption as
those units cause the profile charge imbalance to be only 4% which is
pretty good i.e. the profile is consistent (I assumed pH 7.5 at 20 C).
This water is not very hard (total hardness 89.8 ppm as CaCO3 of which
37 is temporary) nor very alkaline (37 ppm as CaCO3) with a very
modest Residual Alkalinity of 17 ppm as CaCO3 from which an upward pH
shift (relative to distilled water) of only 0.03 is to be expected.
IOW no action should be required to set mash pH with base malts and
even a small amount of colored malt should result in a good value.
The water is well undersaturated with respect to calcium carbonate
i.e. no calcium carbonate would be expected to precipitate upon
standing but somewhat over saturated with respect to CO2 so that gas
can be expected to escape over time with a gradual increase in pH.
It has fair amounts of sulfate and chloride so beers made with it may
have a round, full bodies character and hops will be perceived as
somewhat dry and a bit rough. You couldn't use this water for delicate
continental lagers or similar beers because of the sulfate. There may
be a mineral crispness to beers made with this water and perhaps a
hint of saltiness (does it taste salty from the tap?).
Adding gypsum at the rate of 0.5 gram/liter (12.5 grams in 25 L)
obviously increases the sulfate (to 349 mg/L) and the calcium
hardness (total to 380 while temporary hardness stays the same as the
hardness exceeds the alkalinity) dramatically. The extra calcium
decreases the residual alkalinity to -67 ppm as CaCO3 which predicts a
decrease of mash pH (relative to a distilled water mash) of 0.11 pH.
Because a lot of doubly charged ions (Ca++, SO4--)have been added the
ionic strength changes enough to induce a small pH shift in the water
itself (about 0.02 pH in the acid direction) but the water is still
undersaturated (saturation pH is 7.83) with respect to calcium
carbonate because the alkalinity is so low below 1 mEq/L (50 ppm).
Adding gypsum does not change alkalinity. It, therefore, not likely
that boiling will cause anything to precipitate (as it would in harder
waters with higher alkalinity). Boiling, as a rule of thumb, reduces
hard, carbonate water alkalinity down to about 1 mEq/L (50 ppm as
CaCO3) and this water is below that (even post treatment).
All the information extracted from the basic water report presented
here came from my water analysis spreadsheet which is at
http:/www.wetnewf.org/Brewing_articles/BURP_OCT08
IOW, you can get all this info yourself if you are so inclined though
expect to spend some time trying to figure the thing out. There are
extensive instructions but I know this is complex stuff (based on how
many years it has taken me to get this far).
A. J.
------------------------------
Date: Thu, 19 Feb 2009 09:17:20 -0500
From: "A.J deLange" <ajdel at cox.net>
Subject: Thermal Mass of Mash Tuns
It's been a while since we did the algorithms for ProMash so I'd have
to go back and look at some notes but as I recall the big problem with
pouring hot water into a tun at room temperature is that the water
loses so much heat in the transfer that it throws the calculation off.
Thinking it over it seems a better way might be to fill the tun with a
known mass of water at room temperature, heat the water to a few
degrees above room temperature, let it equilibrate (stand for an hour
or so with occasional stirring) or put some hot water in the tun and
let it stand, with stirring, until its temperature is a few degrees
above room temperature and then add a known mass of water at room
temperature. This prevents heat loss from either the water in the tun
(even if it's a few degrees above ambient some heat will be lost but
the rate of loss is proportional to the temperature difference) or the
water added. Note that I say known "mass" of water. Probably the best
way to do this would be to put the tun on a scale. When its empty you
have its weight (not that you really need that) but you can tare it to
measure the mass of warm water and then take the difference after you
add the cooler water. I'm talking mass here because the volume of a
given mass of water does change appreciably with temperature (several
percent). Another thing to be aware of is that the heat capacity of
water does change somewhat as a function of temperature. I handled
this relatively simply by computing an average over any given
temperature range i.e. if you go from T0 to T1<T0 when you add cold
water the average heat capacity is simply (1/(T0-
T1))*Integral_from_T1_to_T0[Cp(T) dT)]. You can find Cp(T) in
handbooks, Wikipedia etc. Errors induced by ignoring this will be much
smaller than errors induced by ignoring density changes and being
unable to control heat losses.
A.J.
------------------------------
Date: Thu, 19 Feb 2009 08:33:03 -0600
From: Joe Walts <jwalts at gmail.com>
Subject: Re: Thermal Mass
Hey Bill, just a couple of quick and dirty guesses here:
First off, you're not raising the temperature of your entire mash tun to the
desired mash temperature. Instead, you're creating a gradient through the
vessel walls where the inside surfaces are at the mash temperature and the
outside surfaces are at ambient temperature. The latter scenario requires
less heat energy from the strike water, Unless you model the gradient in
your heat capacity calculation, your experiment will result in a lower
thermal mass.
The second complication is the time. How long does it take the system
become stable, i.e. to where you're slowly losing heat to the atmosphere
instead of to the vessel itself? I have no idea, so I just overheat my
strike water by 10 degrees, dump it in the mash tun and wait to add the
grain until the water cools to my desired strike temperature (which doesn't
include the thermal mass of the mash tun in its calculation).
Joe
------------------------------
Date: Thu, 19 Feb 2009 06:56:39 -0800 (PST)
From: Calvin Perilloux <calvinperilloux at yahoo.com>
Subject: Re: Heat calculations and thermal mass
Regarding Bill Pierce's formulas for thermal mash...
That's good research for an English major, Bill! ;-)
> 0.119*32.92 = 3.92
> Unfortunately this is in conflict with the value
> I arrived at (1.918 lbs.) based on my formula and
> experiment with hot water as described above.
You are now into the scientific area best explained by this quote:
"Well, that's great in practice, but does it work in theory?"
Without delving too much into the formulas, and not having my
trusty CRC handbook nearby anyway, I'll highlight a few things
to consider, not only for your setup but for others:
The structure of your vessel can have some significant effect.
In the case of a converted keg, the heavy rings top and bottom
are to some extent isolated from the rest of the body. Sure,
it's thermally attached as one piece of stainless, but my guess
is that the conduction might not be great enough to rapidly
heat those. That would leave the body of the keg absorbing
most of the heat and not the edges.
So in your empirical tests it could show a lower thermal heat
because those outer areas are not being heated (as much).
In other cases, such as people using stainless pots for mash
tuns, the handles are a minimal factor (as above), but keep
in mind that there is often an aluminum layer in the base
(for heat distribution because stainless is such a poor heat
conductor), and this might make it hard to get the results
just right on paper -- do you know how much the alu-sandwich
inside there weighs?
There is also the heat loss that you encounter in bringing
the hot water to the mash tun and pouring it. I find that
this is not that large but definitely not insignificant.
In my own opinion, the very best way to do this is to just
do the empirical work on your own system and use that number.
When you do that, the heat loss, mixed-metal proportion, and
structural features will all be accounted for in your end result.
Calvin Perilloux
Middletown, Maryland, USA
------------------------------
Date: Thu, 19 Feb 2009 10:19:58 -0500
From: Eric Wooten <ecwooten at gmail.com>
Subject: Boston Homebrew Competition - Call for Judges
The 14th Boston Homebrew Competition is coming up on Saturday, February
28th. It will be held at the law offices of Holland and Knight, located in
the Back Bay region of Boston about 2 blocks from the Public Garden (Back
Bay and Arlington Stations are within easy walking distance for those
traveling by MBTA). Preliminary counts yield a total of 271 entries this
year (the entry window is now closed). We are still looking for both
experienced and novice judges and stewards to help with this years
competition.
If you are able to help with judging or stewarding, please fill out the
judge registration form at http://bhc.wort.org/judgereg.shtml.
Further details about the judging process can be found at:
http://bhc.wort.org/judgeinfo.shtml. Although the competition site is easily
accessible by the T and Commuter Rail, on site parking is available and the
competition will cover parking fees for all individuals who register in
advance.
Important Note: As the competition will be held in a secured building,
pre-registration to judge or steward is required. Building security needs a
list of people to provide to their check-in desk in advance of the
competition.
If you have already signed up to help out: thanks in advance for helping us
put on another great competition; Mark Irwin, the judging coordinator for
BHC 14, will be contacting you soon with the final details. If any of you
have any questions please do not hesitate to contact us.
Eric Wooten, Competition Organizer (organizer at wort.org)
Mark Irwin, Judging Coordinator (irwin at wort.org)
Wade Hicks, Entry Organizer (treasurer at wort.org)
------------------------------
Date: Thu, 19 Feb 2009 21:17:27 -0500
From: Kevin Elsken <littleboybrew at verizon.net>
Subject: Thermal Mass
Bill,
First of all, for goodness sakes man, come over to the dark side and
just use the metric system! It is just so much better and easier.
Anyway, I have gone through many turns trying to hammer out thermal mass
values to give consistent mash temperatures. I suspect won't be the
first to mention that your calculation implies your entire mash tun was
heated from 70 def F to 157 deg F. In truth, only a portion of the 32
lb+ tun is actually increasing in temperature from 70 to 157. The
converted kegs have heavy rolled rings around the top and bottom that
most certainly did not change temperature that much. According to the
quick calculations I made, the water lost about 176 kJ, but it would
require almost 361 kJ to raise your mash tun from 70 to 157 F.
Incidentally, insulated coolers are primarily polyurethane foam, which
has a heat capacity of about 1.5 kJ/kg. The trick to the calculation
with an insulated cooler is that due to the excellent insulation value
of the cooler, the outside remains at ambient temperature, so the actual
temperature rise is only about one half the difference between the
inside and outside of the cooler.
Kevin Elsken
Little Boy Brewery
Upper Saint Clair, PA
------------------------------
End of HOMEBREW Digest #5508, 02/19/09
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