Questions on new smokehouse plan

shadders · Apr 14, 2008

Hi,

First post on the forum apart from my intro thread so please bear with me if I ask the obvious.

I'm new to smoking, in fact I'm still working out how to build my smokehouse... I'm keen on cold smoking but live a pretty warm climate.

I have an area near my house that is flat, then a steep incline for about 5-7 metres then flat at the top (about 3m height difference between the two). I'm thinking this would be a good spot to place firebox at the bottom and smoker at the top of the hill.

I'm actually thinking because it's so warm here and I'll only be able to cold smoke in the cooler months that I might run my pipe above ground. The days that are cold enough are short lived here and the ground is so warm (average 22 deg C over the year) that I'd likely get better heat dissipation directly to the colder air rather than waiting for the ground to cool down.
If anyone see's any problems with my theory feel free to jump in...

That kind of rules out clay pipe since it won't be protected or fully supported. Nor will it dissipate heat as effectively as metal would. I'm looking at stove pipe but for 5-7 metres of is awfully expensive. Can anyone suggest any other options?

I was looking at zincalum guttering downpipe. It's usable for flushing rainwater into drinking water tanks so I guess it's foodgrade but can anyone tell me if it's stable at higher temperatures or will leech anything noxious into the food?

I may just have to bite the bullet and pay for the stove pipe but I thought I'd ask here first in case there's an ingenious 2nd option...

erain · Apr 14, 2008

hmm interesting questions, 22C = 71F, how about using foil duct tubing, not familiar with what you proposed but this is rather inexpensive and non plastic,non galvanized. temps gonna be very low so may not be issue anyway but why run a chance. ck out this website has nstructions for converting a bullet smoker to a cold smoker, maybe could apply some of this info. also seen on the net where they run smoke tube thru compartment where jugs of ice are placed to cool smoke down, simply exchange jugs at intervals as needed. just some stuff i found on net....
http://www.virtualweberbullet.com/coldsmoker.html

domn8_ion · Apr 14, 2008

Can't help you with the duct part of the question, but if your in a shady spot, it might help. If not, maybe put some plants around it for some shade and decoration. It might help keep the temps down.

richtee · Apr 14, 2008

The temps at the outlet of the firebox may be high enough to cause concern as far as a galvanized pipe. Perhaps use a length of clay out..then switch to a standard heat duct/HVAC pipe. Custom collers can be made to fit the diameters for a slip-on fitting by any large HVAC contractor.

richtee · Apr 14, 2008

A couple other ideas WRT heat dissipation:

You could pop-rivet or screw "fins" of thin duct metal along the first few feet err... metre of pipe to act as a heatsink.

Or perhaps a small output water nozzle to mist a couple meters of <non jointed> pipe area closer to the fire box.

If the pipe run can be shaded, I'd apply a coat of flat black Hi-temp paint to it. This will also aid in heat dissipation from the pipe.

goat · Apr 14, 2008

I would use the clay pipe. I would not bury it either. If you build a small fire in your fire box and the smoke has to travel 5 to seven meters to get to the smoke house, I do not see any problems. If you keep the smoke below 90*F, you should have no problems. If you need to cool it just wet down the clay pipe and the ground under it with a water hose and let evaporation take over.

I hope this helps and good luck.

cowgirl · Apr 14, 2008

I've used the trench method in the past...dig a trench from the firebox to the smoke chamber using boards to cover the top of the trench.
This was for a section of about 10' though.

Here are some pictures that might give you more ideas...http://www.wedlinydomowe.com/photo_g...es/abratek.htm

Good luck and keep us posted on how your project is going.

geob · Apr 14, 2008

I use the flexable 5" stainless off an old 18 wheeler exhaust. I also used some of the SS pipe. Works great but touch it. I should have gotten the heat shield off the turck but didn't this I would need that. WRONG!!
Just an idea.
geob

shadders · Apr 14, 2008

Thanks for all the suggestions... I've been looking at flexible foil ducting, so far I've found this:

http://www.polyaire.com.au/products_duct.htm#ASSEMBLY

which gives operating specs

and this one show's a price of about $12 for 6 metres. A lot nicer than the cost of stovepipe!

http://shops.adroit.net/premium/meta...420/c422/p6283

I'm thinking with the ultra thin foil walls and the rough inner surface to create lots of turbulence this should be ideal for dissipating heat quickly.

My only worry is whether it's just plain aluminium or if there's something else added to it. And the maximum operating temp is listed as 80c (176 F). I'm guessing the exhaust from the firebox is going to exceed this. perhaps just one length of stovepipe on the way out would help to get the smoke temp down a bit before it starts the long run through the foil tubing...

shadders · Apr 14, 2008

bugger, just called them and it has a mylar inner coating... back to the search...

bb53chevpro · Apr 14, 2008

Here is a link to the same site Cowgirl posted but will direct you "fireboxs". It also shows a few dif diagrams of styles and baffles etc. There are a few in here that you could benefit from letting (directing) the heat in the fire box.
Hope this helps.
Andy.
http://www.wedlinydomowe.com/smokehouse-firebox.htm

shadders · Apr 15, 2008

Thanks for the link... That'll come in handy doing the firebox part...

well I think I've solved the problem...

http://www.westaflex.com.au/_pdfs/vn...t_semiduct.pdf

semi-rigid aluminium duct... It's about $25 for a 3 metre length of 6" so I'll need two but still a lot cheaper than stovepipe. It's rated for up to 250 deg C (480 F) and it's a bit tougher to. The joiners are galvanised but I believe I can fix that by putting them in the fireplace for a few burns...

since it's flexible I might even zig zag it a bit up the hill to keep the airflow nice and turbulent to help with heat dissipation...

richtee · Apr 15, 2008

You'll not have to worry about the galv down the line. Takes temps in excess of like 400Â° f to cause worries

bb53chevpro · Apr 15, 2008

I stand corrected. Thanks Richtee. I thought the temp was much lower than that. Sorry for the incorrect info.
Andy.

bigun · Apr 24, 2008

I am just curious why it would be better to keep the pipe above ground I know the temperature difference plays into it but the soil should still have the ability to absorb more heat quicker. Much like a water cooled engine is more efficient and generally runs cooler than an air colled engine even if the coolant is around 190 degrees and the air is around 70 degrees. I didn't think air was that great at absorbing heat.

shadders · Apr 29, 2008

I haven't actually done the math on thermal transfer rates but given the over all average temp here is 22c and the soil will not vary from that much I might be looking at a soil temp of maybe 16-17c minimum... The soil is quite dry and sandy as well which reduces its thermal conductivity.

So on a cold night I might have air temp of 5-8 degrees and a soil temp nearly 10 degrees warmer... I think I'll basically need to take advantage of the temp extremes to get cold enough... i.e. night time in spring/autumn and maybe some parts of the day in winter... summer forget it, you're lucky if you get below 20c in the middle of the night... Soil's high thermal mass tends to dampen the extremes of the temp fluctuations to a smoother curve... i.e. higher low temps and lower high temps...

water cooling is much more efficient because the liquid is higher density = more molecules in contact with the heat source to carry it away... but both air and water have the advantage of flowing warmed up molecules are constantly being replaced by cool ones. Soil doesn't do this... actually soil is a pretty average heat conductor...

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