Where to place my fan in home build

[smokebandit]

Wooden smoker that uses a propane turkey fryer for a burner. I will have a fresh air intake at the bottom and an adjustable vent at the top.

Internal space in the smoker is about 20 cubic feet.

I'm unsure where to place the fan.

I have seen commercial smokers place the fan on top sucking the heat and smoke up and out.

I have seen homemade smokers have a fan blowing into the smoker just above the burner to circulate the smoke and heat. I have also seen the fans have way up.

Where should the fan be?

 

[dirtsailor2003]

If you are using a propane burner for your heat source you won't want a fan. You just need good adjustable air intakes down low and a fully open outlet up top.

 

[smokebandit]

ok I'll try it without the fan first.. If needed I'll come back for my advice

 

[bill1]

To me the advantage of the fan is you can have a way of predicting air flow rate (in, say, CFM) vs fan input setting (e.g. voltage). If you also have a mass flow sensor on your gas, you then have a quantitative way to play with mixing gas and O2. Presumably the best combustion mix (as a Chemist would tell you) would also give the best meat flavor, but that depends a bit on the size of your burner vs the size of your smoker, how big the tray is that holds your flavor pellets, chips, etc, and where it sits in relation to the flame, etc., etc.

Most folks would rather just look at the flame...the shape and color, tells you a LOT and experience will teach you the best air/gas mix of flavor, gas economy, etc. But you need to do this in normal (doors closed) operation. So I'd say it's important you can see your flame at any time. This argues against fans and for openings you can look into. (A couple cosmetic mirrors at 45degrees can "turn" the light so you can see it easily and safely.)

But you DO need a control on the gas flow...it's your main temperature control knob...and that requires then some control on the air flow as well. Like DirtSailor, I agree your best air throttle is down low (on inlet) and the exhaust should always be 2-3 times the area of your inlet. And of course your air inlet should be where your gas jets are, since that's where it's needed. So round burners in the center of a smoker with a single (adjustable size) hole in the bottom center works well.

This gets you on your way. Now if you want some automation to this (like set a temperature and walk away for hours) or you want highly-regulated (<20 deg temp swings) you'll need an adjustable fan and gas controller or at least a motorized control on the air damper (inlet throttle). But that's a massive amount of work for only occasional (hobby) smoking and it's probably easier to just get an electric smoker or a pellet burner if that's really important to you.

So watch your flame, temperature, and air inlet and have fun.

 

[smokebandit]

OK so I've built my smoker and used it a few times as is.. Here are some issues I'm having and things I've tried

1) Doesn't produce enough smoke. We smoked a chicken and ribs seperately, both were not smokey enough. We've done both on a commercial smoker and it was much smokier and better.
Ideas for this
-not enough wood chips-> We used lots each time.
-space inside smoker is quite bit, so smoke might not be filling it enough. We tried more heat to burn more wood chips, but smoker got too hot.
-We tried putting the frying pan that holds the chips on top of the flame more, but the wood chips light on fire.
-too much draft sucking smoke out? I tried closing the top vent, but then the burner goes out.


Ideas?

2) Temperature from top to bottom is about 30 degree difference, top being the warmer.
-I tried playing with the vents, but I think I need a fan.

ideas?



3) burner can't go low enough without going out.
-I haven't tried it yet, but I was thinking of making the fresh air intake larger, but I don't want to do this yet if I need to add a fan anyways.
-Another thought it adding a steel tube in the fresh air intake so that the fresh air comes into the smoker right at the burner. As is, hole is about 8 inches from the center of the burner.

Ideas?



I think a small variable speed fan pushing fresh air into the smoker will solve all my issues.
-the fan could force more fresh air to the burner, so I can close the top vent to keep some smoke in.
-fan would circulate the heat more to make it more even.
-fan would allow the burn to burn lower without going out.

 

[smokebandit]

Another option I just thought of to fix my problems

Add a internal fan for circulation. This fan will move air around inside the smoker, but won't be pushing fresh air in.

In addition, increase the size of the fresh air intake.

 

[bill1]

A convection fan inside, running slow, like convection fans in kitchen ovens, should help both your temperature spreads in space as well as put more smoke flavor in your meat. The idea is that using the natural draft, a smoke molecule pretty much follows the path of least resistance and goes straight out the stack. If the meat is along that path, a few stick to the meat for flavor. A convection fan just tries to put one or more added up & down loops to the path of those molecules. More chance to stick to the meat and keeps the internal temps more uniform. You don't want a lot of flow, just mix up the air you have a little better.

Most fans don't like heat so you'll want metal blades with a long shaft that can go through your case, and then keep the motor outside where it's cooler. Think about the flow...a fan has an inlet side and an exhaust side. It's most efficient when mounted in a plate and with ducting on both sides. (Note how they do it in kitchen ranges.) But for a quick expt you can mount it on top with an extra long shaft, sucking air up the middle and blowing it back along the outer walls after bending it over at the top. But you'll want to make sure you're not just helping blow the smoke out the existing exhaust...that's not what you want if you want more smoke flavor.

Most propane smokers work better with chunks instead of chips. You may need to put the pan then even closer to the flames. If you find you really prefer the chips but they keep flaming up, put a steel plate with just a few holes over the pan, or a ventilation louver, or something to limit how much air can rush into the pan.