What is the speed of good airflow in a smoker?

[Its_Raw]

Hello, all!

The obvious answer to this question is whatever turns out good food, but I would like to see if it can be quantified a bit. Have you read, or do you have an anemometer and know, the mph of airflow out of the stack when you believe your smoker is drawing air efficiently? Is it 2mph? 4 mph? Just curious.

Thank you!

 

[Newglide]

You should check out this video,
He had the same question. He explains airflow and used one on the stack but it didn't turn out so good because it was plastic and melted

 

[Its_Raw]

Newglide - I watched that video a while ago and noticed he melted his rather quickly. I have one and I just hold it over the stack long enough to get a quick reading. Only takes a second or so. Since the heat coming out of it is warm, but not necessarily hot, I am not sure how his stopped working. I am hoping others have had some success maybe. Just curious as to what the airflow rates might be.

 

[Smokin Okie]

I have a cheap hand held anemometer . I tried to use it one time, but the Franklin stack is too tall. I need to get a step ladder to use it and I've never gotten around to it.

I would like to know if there's a measurable increase in air flow with the Franklin firebox door open, compared to the door closed.

I just have to rely on what's visually coming out of the stack ...

 

[Its_Raw]

I would love to know those numbers as well and the internal temp at the time of the measurement.

 

[Chasdev]

So, speed or volume?
Which are you (we) after here?
If you seek higher speed, reduce the diameter, air will move faster, but less moves through.
The guys that design piston engine racing exhaust pipes have all the math down on paper if one cares to read up on it.
They get tangled up in reversion pluse wave tuning, so it gets a tad wonky.

 

[Smokin Okie]

I would love to know those numbers as well and the internal temp at the time of the measurement.

You can see the temp in that IG post, the analog gauge is reading 250* , or thereabouts.

 

[Its_Raw]

Chasdev, I am not seeing to increase or decrease velocity. I simply wish to measure the velocity of the air exiting the stack (because velocity is the easiest measurement to obtain) to see how various pits perform at a certain temperature.

 

[Florida Chris]

Chasdev, I am not seeing to increase or decrease velocity. I simply wish to measure the velocity of the air exiting the stack (because velocity is the easiest measurement to obtain) to see how various pits perform at a certain temperature.

I think Chasdev was leading you in the right direction with that post and question. Speed of airflow is just 1 part of the equation.

What you really need to know is volume of airflow. CFM. A 500 cu/in grill with a 2.5" stack will have much less CFM than a 1000 gal smoker with a 6" stack. But it's air turn-over that matters. You need to get that stale smoke out while still letting it linger long enough to make friends with the meat. And also draft properly to keep the fire burning at a consistent rate.

I'll give an analogy I use sometimes when I get into a "conversation" with people about cars. Horsepower vs. Torque.

Horsepower is a mathematical formula based on RPM. In theory you can have a 200 hp motor that you can stop with a pair of pliers.

You can also have a motor that turns 0.1 RPM at 200 ft/lbs of torque that you wouldn't ever be able to stop with pliers.

CFM is similar. Air moving at 1 mph through a 1" pipe vs. the same 1 mph through a 10" pipe. The volume through the 10" is going to be much greater. And that's where smoker volume comes in to the equation.

Speed of the air alone will not give you the enlightenment your looking for.

 

[Smokin Okie]

Maybe just me, but I don't want an exact measurement to compare with other smokers. I just want to compare with the firebox door open and door closed.

 

[Its_Raw]

Lets not get too deep in the weeds. I just want to have a ballpark idea what other smokers are doing - at a consistent temperature Franklin puts out air at X mph, a Yoder does X mph, an Old Country does X mph... I can look at the specs of each and surmise why one might have a higher or lower mph depending on the obvious variables.

 

[Chasdev]

IF somebody would just publish a spreadsheet with all the successful offset cooker's airflow specs.....
I would love to do it, so I'm officially submitting soliticitaions for funding donations!
Send me enough money to buy every top line cooker and I WILL publish the test results!

 

[Up_In_Smoke]

Lets not get too deep in the weeds. I just want to have a ballpark idea what other smokers are doing - at a consistent temperature Franklin puts out air at X mph, a Yoder does X mph, an Old Country does X mph... I can look at the specs of each and surmise why one might have a higher or lower mph depending on the obvious variables.

So go buy a $20 anemometer and go around measuring all the smokers you can find.

Measure yours and then make modifications and see how things go.

 

[Chasdev]

Don’t measure mine..I already know it sucks!

 

[SmokinEdge]

Lets not get too deep in the weeds. I just want to have a ballpark idea what other smokers are doing - at a consistent temperature Franklin puts out air at X mph, a Yoder does X mph, an Old Country does X mph... I can look at the specs of each and surmise why one might have a higher or lower mph depending on the obvious variables.

I just have thoughts,
The air flow is variable, never really optimal as a defined number. This is because many physical things are at play all the way through the cook and must be adjusted for, this is why it takes time to become a “pitmaster”. No amount of electronic equipment or gadgets will pull your curve up.

Variables, like pit volume, meat volume actually in the pit at cook, ambient temp, wood type to a degree, ambient humidity, and there are more but many variables.

As the pit comes to temp with vents all wide open (high air flow) we control temp by coal bed size and intake air. The hotter the coal bed the stronger the draw (function of hot air rising, the hotter the faster) we control this by reducing intake. As the temp goes down we may increase intake as we add fuel, then reduce intake as we stabilize temps, again it’s a variable air flow. This knowledge is being a pit master. Nothing per se is ever set solid on a bbq pit. Temp swings are normal and ambient changes are normal, changes in meat load change just so many variables. No set and forget. Just my initial thought.

 

[Its_Raw]

SmokinEdge, I understand, I am just wordering what some rough numbers might be despite the variables to satisfy the numbers nerd in me, nothing more.