17 Nov
2003
17 Nov
'03
8:50 p.m.
not to beat a dead horse but I used to boil w a ss keg and switched
to a same sized alum kettle 1/2 the boil time! I can boil in about 30
min instad of 1 hr this is one big improvement. this is with a 13 gal
boil. also the price of a purchased (opposed to a homemade )
container is 1/2 I say alum rocks!!
----- Original Message -----
From: "Rick Oftel" <Rick.Oftel(a)toro.com>
To: <jellings(a)me.umn.edu>; <mba(a)thebarn.com>
Sent: Monday, November 17, 2003 12:32 PM
Subject: Re: Kettles, Cleaners, Conductivity.
Jim, Not trying to debate science but your response
generated a question
that I hope is easily answered about thermal conductivity.
Possibly an
experiment over a beer would be helpful.
Trying to better understand the aluminum vs SS debate. Some folks use
Rocket
Engines to heat kettles. Others use electrical elements. A few of
us rely on small gas burners that seem to outperform many of the higher BTU
producers.
According to your statistics, aluminum is 11.25 times more conductive than
SS. Is
it accurate to state that an aluminum stock pot would transfer 11
times more heat to the liquid that the SS version using the same external
heating device? Would it be logical to conclude you would use 11 times less
input heat with aluminum than SS to achieve the same degree of "rolling
boil?"
To validate this, would a "heat to boil race" be appropriate? Two gallons
in aluminum, two gallons in SS. Original water temperature 60°F. Similar
profile containers with identical burners (15 kbtu). Both burners started
at the same time. If the aluminum boils in 5 minutes, then the SS boils in
56 minutes?
I have never had trouble with scorching but use a diffused flame source
with about
100 single hole jets. I do notice more accumulations of beer
stone, hard calcium deposits (white), and general brown crud directly over
the iron supports. They must significantly help with heat transfer.
The false bottom for boiling is usually used only when you bitter with
whole hops.
The nice thing is it does not need to be in the boil for the
complete cycle but performs very well with Irish moss. If it is not yet
installed, you can scrape clean the bottom of the kettle and cut back even
more on your input BTU's. If you leave a little space between perforated
plate and edge, you get a great roll in your kettle and the perforations
appear to hold the hot break quite solidly.
Must be experiment time. Stay tuned - don't touch that dial! I look
forward
to data about flame impingement and actual heat transfer!
Thanks Jim for kicking this off again!
Rick O
Rick Oftel
>> "Jim L. Ellingson"
<jellings(a)me.umn.edu> 11/17/03 11:13AM >>>
Greetings,
I started out w/ Keg-kettles w/ heating elements and spigots.
I direct fired the kegtle, in addition to the electircal heat.
Never did a decoction in these elemented kettles, can't
really stir w/ the element in place.
The Polarware SS Kettles are much better than converted kegs.
For a direct fired brew kettle, I find aluminum to
be superior to stainless. Isssues as I see 'em.
1. Conductivity, hot spots, scorching:
Materail Conductivity Cost
(W/m-^C) (From Matweb)
Copper 360 $1kb?
Aluminum 180 $100
400 SS 27 $100
300/18-8 SS 16 $200
I've never used copper, but in my experience, aluminum is
a superior conductor compared to SS.
Granted the Al needs to be a bit thicker, so the actual conductivity
may be only 5 times the values for the Polarware pot. The chances
of scorching are much lower w/ aluminum. Aluminum works much better for
decoction mashing. A thicker, better conductor means fewer/no hot spots.
2. Cleaning. Commercially, aluminum is not a good option since
the commercial cleaners (strong caustics) dissolve aluminum, but
few compmercial operations are direct fired. Also, commercial
brewing is a high risk occupation. (get the numbers from OSHA
if you don't believe it.) Number one hazard is burns, from the
strong caustics used in cleaning.
My question is this. What sort of chemicals are you using
on your home brew kettle? Why?
My aluminum kettles take a bit of beer stone, and keep
it until I over-do the acid/pH adjustment.
3. I'm not a fan of spigots in the brewkettle. Impossible to clean,
and easily plugged. I like the siphon/duck/whatever.
4. I'm not a fan of false bottoms. Never worked that well
in the mash tunn (Sabco), so I'm back to slotted pipes in a
cooler. In the kettle, I've had trouble w/ scorcing under
the false bottom (Sabco). Quite possibly, that issue is
reduced or eliminated w/ a "real" kettle. (e.g. Polarware).
5. Flavor: Not an issue. See Jeff Donahue's article on same.
My keg kettls are wired for heat (1100 watts at 110v) and have
spigots. I've retired them "upstairs) to HLT use, and they
work fine for that. A spigot on the HLT is very convenient.
I'm as big a fan of stainless as the next guy, but it's
not a very good conductor.
Cheers,
Jim
--
------------------------------ *
* Dr. James Lee Ellingson, Adjunct Professor jellings(a)me.umn.edu *
* University of Minnesota, tel: 651/645-0753 fax 651 XXX XXXX *
* Great Lakes Brewing News, 1569 Laurel Ave., St. Paul, MN 55104 *