Building a smoke house/ outdoor wood boiler

Tracy · #1 10/13/10, 08:49 AM

Need some expert advise. We make dehydrated all natural pet treats as part of our pet food business.

We want to build a smoke house using panels from a walk in freezer. This would be built outdoors next to our Central boiler.

The boiler has 3 different zones. One is for the house and hot water, one is for the shop and the other I want to use for the heat source in the smoke house.
Temp needs to be 120 degrees or higher. What I want to use this for is drying meat [not smoking] like a big dehydrator.
This is where I am stuck, would a water to heat exchanger get hot enough to maintain that temp?
If not what could be used. I run commercial electric dehydrators now but it would be ideal if you could use the wood boiler instead and cut down on electric usage.

Any other suggestions would be appreciated. Am I missing something? Also any good plans for building?

Thank you,
Tracy

heavyrebel · #2 10/13/10, 09:23 AM

Tracy, does your pet food have a website?

uncle Will in In. · #3 10/13/10, 09:33 AM

How hot is the water comming out of the boiler? If your idea didn't keep the temp up to 120, you could use electric to bring it on up. Wouldn't take nearly as much electric as now and would give you the advantage of having the top temp controled.

ronbre · #4 10/13/10, 09:40 AM

don't know, I think if you ran it on a thermostat it might, but it might also make your other buildings too hot !! not sure...we have a wood boiler as well and when our son turns up his, ours gets so hot it has to keep running to take the excess heat off the pipes so there isn't a boil over..and we have had quite a few boil overs but our house runs constantly when the water gets too hot..so we end up opening doors.

Tracy · #5 10/13/10, 09:57 AM

Quote:

Originally Posted by heavyrebel

Tracy, does your pet food have a website?

http://www.hare-today.com

Tracy · #6 10/13/10, 10:01 AM

Quote:

Originally Posted by ronbre

don't know, I think if you ran it on a thermostat it might, but it might also make your other buildings too hot !! not sure...we have a wood boiler as well and when our son turns up his, ours gets so hot it has to keep running to take the excess heat off the pipes so there isn't a boil over..and we have had quite a few boil overs but our house runs constantly when the water gets too hot..so we end up opening doors.

Never had had any issues with boil over running the 2 zones now.
I guess what I am trying to figure out is if the heat exchanger would hold this higher temp. Being that we are using freezer panels to biuld this it would be well insulated so I am thinking that once we had the temp up to 130 degrees it would hold the ehat fairly well but I am not sure if the exchanger will get that high or what type of thermostat woudl be used for that high of a setting.

We heat our pool with a water to water exchanger in the summer and I can set that thermostat for 100 degree is I want. A big hot tub so to speak.

Tracy · #7 10/13/10, 10:04 AM

Quote:

Originally Posted by uncle Will in In.

How hot is the water comming out of the boiler? If your idea didn't keep the temp up to 120, you could use electric to bring it on up. Wouldn't take nearly as much electric as now and would give you the advantage of having the top temp controled.

Water setting can be set for 180 degrees for the boiler.

ROCKIN R FARM · #8 10/14/10, 01:52 AM

just thinking out loud here but.... large car radiator, electric fan, and a temp control switch to turn the fan and water flow on at say 115 degrees and off at say 125 degrees
if well insulated it shouldnt cycle very often . also fan could be the 12 volt kind used in automotive applications which would reduce the energy use considderably

||Downhome|| · #9 10/14/10, 03:36 AM

little more specifics maybe Tracy,

how big of an area needs to be kept at temp?

you are going to need air change to remove the extracted moisture and that will remove heat as well.

I would think auto radiators would work, though i think the old style cast iron ones would be better, you could even make your own with black pipe. which ever you decide I would think that it should be continuous circulation on its own loop.

from what I can figure out the boiler gets up to 180 degrees.

as a different option maybe a solar system with the boiler as backup. be more convenient in the summer.

**Ross** · #10 10/14/10, 04:57 AM

Heating air with hot water is complicated the hotter the air the lower the temperatrue rise. So air entering at 50f running hot water @180f you could easily expect an 80 to 90 degree rise, but the hotter the air entering the lower the rise so as the first 1000 cfm (how big is the dehydrator, 20,000 cubic feet?) rolls through the rad it picks up alot of heat, then its warmer coming in and the temp rise falls, so now you're heating 70 degree air so it only has a temp rise of say 75f and as the air temp goes up even more you extract less and less heat from the hot water source. From a practical point of veiw I'm guessing you aren't going to reach 120f using 180 water while exhausting moist air even with a huge heat exchanger and lots and lots of fans. So I wonder if making your shelves slotted and having long narrow rads like out of walk in coolers right under them so the 180 boiler heat is concentrated at the product and the rising hot air vented. Maybe you could even work in an HRV to help recapture some lost heat? I'm assuming your other heated areas are controled by thermostats but if those heat exchangers are set to use 180 degree water you could have issues like Ronbre faces. They're fairly easily fixed by reducing fan speed or adjusting water flow but fussy.

michiganfarmer · #11 10/14/10, 06:40 AM

I have thought about hanging meat right in my outdoor wood furnace to smoke it. Part of the time the furnace is only smoldering anyway

artificer · #12 10/14/10, 08:46 AM

More information is needed. What size is the dehydrator going to be? Ross's 20,000cubic feet seems... high. (50'x50'x8') If he meant 2,000sqr-ft, its much more reasonable, but thats still almost 16' x 16'. How thick are the walls, and what type of insulation does it have?

The next thing we need to know is how much material is going to be put into the dehydrator, and how long is the drying time?

Hot water coils for heating are usually 1-2 row type, and take incoming air at 60degF or so, and heat it with 140-200degF water. The difference in water temp is high, so its easy to do.

Chilled water, on the other hand, uses water that is typically only 45degF, and they want 55degF air temps out. This means they get to within 10degF temp difference. The way they do it is by using more rows of coils. You can either buy a commercial coil, or just stack two or more truck radiators. Commercial chilled water coils typically have 3-10 rows of coils.

IF your water is at 180degF, then I see no problem getting 120degF air out. A double row radiator from a truck or high performance car should work fine.

The next thing to know is what the outside temps are going to be. This tells you how much heat is needed to get to the 120degF, as well as how much heat is lost through the insulation.

One way of building the system is to put up the shell. Make an air box that contains a blower, air filters, and coils/radiators. The air will come from the dehydrator, and return to it. The box can be either inside the dehydrator (simpler) or outside. An exhaust port get put into the dehydrator on the opposite side from the air box. Ducted in the air box inlet is a duct to the outside. A damper get placed in the air box to controll the amount of makeup/fresh air you get. Open the fresh air inlet damper, and close the recirculating damper, and most of the air is fresh, and takes more heat get to temp. Another option is to put a permanet restriction on the recirculating inlet, and put a damper on the exhaust port. (sliding piece of wood...)

So, to make a long story, short... (way too late for that) yes, its possible to make a system. Fairly easy to do if you can handel the plumbing and ducting work.

Michael