Hank Murrow on sat 13 aug 05
On Aug 13, 2005, at 12:17 PM, David Hendley wrote:
> Hi Joe, I can't give you any formula, but just be sure you do not
> mis-interpret mel and Hank's advice about small flue sizes
> being more efficient.
> They are writing about GAS kilns, not wood. Wood fired kilns
> need larger exit flues and larger chimneys - no doubt about it.
Dear Joe;
David Hendley tells it like it is. My Doorless Fiberkiln with a flue
area of 19.6 sq.inches is possible because it is very efficient, firing
on one medium size Eclipse mixer of around 140,000 BTU. LEss energy in
= less exhaust out.
Cheers, Hank in Eugene
www.murrow.biz/hank
Joseph Passofaro on sat 13 aug 05
Is there any ratio or formula for the total area of exit flue to the
collection box in proportion to the chimney exhaust area for a wood fired
kiln? The designs I have seen seem to be very large in proportion to the
chimney exhaust area. Is there a reason for this? Any help would be
greatly appreciated.
Joe Passofaro
Paul Herman on sat 13 aug 05
Hi Joe,
I don't know of any formula to tell you "the best" ratio, but will
include measurements from our woodkiln for an illustration.
Air inlets: 20 sq inches
Flues to second chamber: 305 sq inches
Flues to chimney: 246 sq inches
Chimney: 305 sq inches, but we only run the damper about half open, so
we actually use up to 150 sq inches.
I think one of the reasons they seem so large on the woodkilns you've
seen is that wood takes a lot more air than gas to burn. Also, it's good
practice to design in extra capacity if you are building a hardbrick
kiln. It's easy to make a "too large" flue smaller by simply bricking it
in a little. However, if the flues are too small, well get out the
sledge hammer, chisels, grinders, wrecking ball, etc. Also your dust
mask and moon suit.
Two books I recommend are Jack Troy's book on woodfiring and the one by
Minogue and Sanderson. There are lots of drawings of wood kilns that are
in use.
good firings,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: Joseph Passofaro
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: wood fired kiln exit flues
>Date: Sat, Aug 13, 2005, 7:52 AM
>
> Is there any ratio or formula for the total area of exit flue to the
> collection box in proportion to the chimney exhaust area for a wood fired
> kiln? The designs I have seen seem to be very large in proportion to the
> chimney exhaust area. Is there a reason for this? Any help would be
> greatly appreciated.
>
> Joe Passofaro
David Hendley on sat 13 aug 05
Hi Joe, I can't give you any formula, but just be sure you do not
mis-interpret mel and Hank's advice about small flue sizes
being more efficient.
They are writing about GAS kilns, not wood. Wood fired kilns
need larger exit flues and larger chimneys - no doubt about it.
David Hendley
I don't know nothin' but the blues, cobalt that is.
david@farmpots.com
http://www.farmpots.com
----- Original Message -----
> Is there any ratio or formula for the total area of exit flue to the
> collection box in proportion to the chimney exhaust area for a wood fired
> kiln? The designs I have seen seem to be very large in proportion to the
> chimney exhaust area. Is there a reason for this? Any help would be
> greatly appreciated.
>
> Joe Passofaro
Louis Katz on sat 13 aug 05
I have long thought that closing a damper was not as good a solution as
restricting the flue where the chimney attaches to the kiln. This would
cut down on radiant heat loss. In fact I have owndered if an oversized
chimney and a small exit flue might be a good choice as it would also
tend to increase turbulence in the kiln.
Louis
On Aug 13, 2005, at 2:17 PM, David Hendley wrote:
> Hi Joe, I can't give you any formula, but just be sure you do not
> mis-interpret mel and Hank's advice about small flue sizes
> being more efficient.
> They are writing about GAS kilns, not wood. Wood fired kilns
> need larger exit flues and larger chimneys - no doubt about it.
> David Hendley
> I don't know nothin' but the blues, cobalt that is.
> david@farmpots.com
> http://www.farmpots.com
>
>
> ----- Original Message -----
>> Is there any ratio or formula for the total area of exit flue to the
>> collection box in proportion to the chimney exhaust area for a wood
>> fired
>> kiln? The designs I have seen seem to be very large in proportion to
>> the
>> chimney exhaust area. Is there a reason for this? Any help would be
>> greatly appreciated.
>>
>> Joe Passofaro
>
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>
>
Louis Katz
http://www.tamucc.edu/~lkatz
Lee Love on sun 14 aug 05
>
>
> Joseph Passofaro wrote:
>
>Is there any ratio or formula for the total area of exit flue to the
>collection box in proportion to the chimney exhaust area for a wood fired
>kiln? The designs I have seen seem to be very large in proportion to the
>chimney exhaust area. Is there a reason for this? Any help would be
>greatly appreciated.
>
>
Joe, Like Paul mentioned, woodkilns have different requirements
compared to gas or oil kilns. Various types of wood kilns have
different requirements too. Along with the books Paul mentioned, I
would also recommend Fred Olsen's The Kiln Book.
Also, like as Paul points out, it is easier to make a flue exit
smaller than it is to make it bigger. And you don't have to depend
only on a shelf damper to adjust the draft, but you can also use pull
bricks as passive dampers.
--
Lee Love
in Mashiko, Japan http://mashiko.org
http://seisokuro.blogspot.com/ My Photo Logs
"The way we are, we are members of each other. All of us. Everything.
The difference ain't in who is a member and who is not, but in who knows it and who don't."
-- Burley Coulter (Wendell Berry)
Ron Roy on sun 14 aug 05
Hi Louis,
My thoughts as well - I made a mental note to ask Nils about this next time
I see him,
What can possibly be the diff? Some dampers are only inches from the kiln.
RR
>I have long thought that closing a damper was not as good a solution as
>restricting the flue where the chimney attaches to the kiln. This would
>cut down on radiant heat loss. In fact I have owndered if an oversized
>chimney and a small exit flue might be a good choice as it would also
>tend to increase turbulence in the kiln.
>Louis
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Linda Ferzoco on sun 14 aug 05
So guys, are you saying that perhaps a damper that operated like the shutter
of a camera would be better?
>
>>I have long thought that closing a damper was not as good a solution as
>>restricting the flue where the chimney attaches to the kiln.
Louis Katz on sun 14 aug 05
I was not saying that. I do think a smaller flue is better than a
restriction further up the chimney.
Louis
http://www.tamucc.edu/~lkatz
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