Air flow theology

Ivan, My new 'convection' oven was supposed to do 5 racks of cookies at one time. Hah, the top and bottom racks burn before the 3 center ones bake properly. Conclusion, the one fan in the rear center is NOT enough! For your smoker, I'd put a matrix of 9 fans, 3 by 3 to form a 'wall of hot smokey air in motion'. If you use a convection oven as a start or steal the door off of it, you might be able to see the air flow pattern, maybe 4 fans will be enough. The trick is to get a more even air flow and more fans will do that.

hth jay

I happend into some Audel books on hvac in a 2nd hand bookstore, they gave some basic arithmetic for sizing & locating blowers and ducting for various purposes- no exotic math it seemed to be a compilation of practice. I found it pretty easy to understand.

Probably not, IIRC, the book touched on arrangements like this. If you want the air spread out, you have to really spread it out, sort of like an aquarium aerator, and suck it in a similar fashion. Since there's very little pressure differential from the duct to your space, the air stream isn't going to disperse much.

You might have better luck adding a bunch of smaller ducts on your intake and exhaust sides- so instead of one big stream in the middle you get more smaller ones dispersed accross it. Naturally the smaller ones have greater air resistance, you really can never win with this sort of thing... Since its simpler, it might be worth a try putting in a circulating fan to see if that improves matters.

Gregm

"Air flow theology".......

Damn!

These religious cults are getting stranger and stranger...............

How about a vertical conveyer to keep the racks slowly moving around in the chamber? 180 degrees isn't a horrible condition for a mechanical system and the motor and controls could be outside.

Richard Coke

The Church of the Divine Draft....

"To be civilized is to restrain the ability to commit mayhem. To be incapable of committing mayhem is not the mark of the civilized, merely the domesticated." - Trefor Thomas

"Bob Paulin" wrote: "Air flow theology".......

Yeah! PRAY tell us what this means. (Did you mean air flow teleology?)

Thanks, I'm googling Audel right now.

Okay, that answers my question.

That confirms what I thought also. I was thinking of pushing the air through a wall with a matrix of holes. On the opposite side of the smoker would be a receiving matrix.. To further fine tune each individual row of holes, I could have a sliding strip of sheet metal with holes cut in it also. Like you said, similar to an aerator. Does anyone feel like building something like this for me to test? Just ship it to Canada. :oD I work at a gourmet food processing factory where they are trying to crack into the jerky business. They are having similar problems with their huge industrial smoke houses.

Ivan.

Thanks

Sounds good, send me the plans! :o)

Look at a local hot dog place. The hot dog warmers sound like what you need, although on a bigger scale.

If you just put a sheet of holes in front of a single big inlet, I think you're still not going to achieve very much- the lack of pressure differential will make the air mostly just slide on through.

My guess is you'll have to get some real ducting in there- maybe a bunch of 6" diameter stuff, coupling back to a manifold. The idea being you're forcibly dividing the air up into a number of streams. This is likely better than a simple screen because you're adding air resistance by the manifold and ducting, yielding a bigger pressure differential divided over fewer holes for the air to go. You'd probably still need dampers on the duct outlets to compensate for the stuff in your smokehouse that interferes with the airflow.

You may well need something similar on the exhaust side, or your nice streams of air will funnel down like a cone.

I imagine a test manifold could be a plywood box, maybe in some proportion to the cross section of your smokehouse, a few feet deep with some number of 6" ducts, a few feet each, feeding the smokehouse. You might be able to be clever and arrange the ducts so those with the shortest path to the blower have the longest path to the smokehouse exhaust- in an attempt to keep the airflows balanced. This is of course off the top of my head, even the simplest table lookups and calculations will probably do better.

I think circulating the air or the product within the smokehouse is probably a better idea. Have you tried using fans?

Gregm

No, I haven't tried using fans yet, because our existing smoke house doesn't have the area needed to mount them without greatly reducing the payload area. But I'm tending to agree with using fans.

Yess! And just what is " teleology " ?? At least theology is a word I recognize. :-) ...lew...

Lewis Hartswick wrote: Yess! And just what is " teleology " ?? At least theology is a word I recognize. :-)^^^^^^^^^^^^^^ You had me worried, Lew, so I rushed over to my Webster's Unabridged to verify that the word is really there. And now I'm going to try to remember what I read: Teleology--the fact of being directed toward an end or shaped for a purpose, usually applied to natural processes. (Such as the design of air circulation systems.)

This would be my suggestion as well . How about hanging cradles suspended between two large diameter wheels inside the smoker ? Motor and electrics can be on the outside with only the shaft protruding ? I imagine the wheels could be simple plywood disks thick enough to carry what ever the weight requirement would be . The cradles open wire racks and as long as they hang lower then the pivot point . Seems a resonably inexpensive solution . Luck Ken Cutt

And turbulence, lots of turbulence. You don't want a smooth low restriction air flow. You want a rough turbulent flow. That distributes the air more uniformly about the chamber. (Well, at least it will if you design it right.)

Gary

A "brute force" method might be to have a plenum or manifold with a pattern of fairly small holes or slits. The idea is to have the pressure drop across the openings considerably more than any drop due to air flow within the plenum so the pressure in the plenum is relatively uniform. The air velocity and volume through the various openings would then also be relatively uniform.

A disadvantage to this technique is that it takes more energy (higher pressure blower) to operate than a multi-ducted distribution system, but it's simple and wouldn't take much space.

Thanks Leo. Hardly a day goes by that I don't learn something new here on RCM. My handy desk dictionary didn't have it. ...lew...

Something similar to a ferris wheel might work... with extra racks going up the 'spokes' to take advantage of all the space. This device would sit in a 'horseshoe standing on end' shape. Air would blow down from the front upright on the horseshoe, and exhaust on the other end of the horseshoe. This will allow air flow on both sides of the racks, the top side will probably still dry faster. You could put the heat source on the bottom to compensate. The shape for the horseshoe in the loading area side would probably have to be on some type of hinge to be put in place when the machine is ready to operate. The racks would slide into guides for easy access and loading/unloading. The speed of the device could be controlled using gearing. Just hit the timer switch to turn everything on....

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