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Info On Centrifugal Roasters???
seedlings
John, the whole centrifugal aspect is such an effecient method of transferring heat to the beans, I bet LESS heat is actually required. The sides of the bowl shouldn't be any hotter (and probably less hot) than in a nice drum.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
farmroast
I noticed that in the article on centrifugal roasters they mention a roasting gas. When I was working on my roaster I had a thought about wind burn or the effect of high speed oxygen on the surface of the bean. My pot has about a 3' circumference and I generally run about 200rpm, 10'/sec.(240rpm top speed) but didn't put a higher speed motor motor in due to this concern. Could super high speed air contact cause a negative effect to the bean surface :( ?
farm
Ed B.
DreamRoast 1kg roaster, Levers, Hand Mills http://coffee-roa...gspot.com/
 
seedlings
OK, David, what am I doing wrong? I can open your deep dish chart (and I had hoped it was pizza recipes, dang it) but with Jim's, it keeps telling me the file is corrupted. I can download the zip folder and see the eXcel and PDF files in it, but if I try to open one or "extract all" then my computer pukes out a helpful message saying the file is corrupted. I know it's only my dHell craptop that's corrupeted. Well, and the wireless card. And the small-town AT&T service. But not the file.

If anyone has a moment to e-mail it to me, that'd be pretty sweet.

[email protected]
CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
EddieDove
Hey Chad,

I sent you the files ... see if those work ...
Respectfully,

Eddie Dove

The South Coast Coffee Roaster
vita non est vivere sed valere vita est
Home Coffee Roasting Blog and Reference
http://southcoast...gspot.com/
 
http://southcoastcoffeeroaster.blogspot.com
Dan
Could super high speed air contact cause a negative effect to the bean surface?


Ed, I dont' see how. The purpose of convection heating is to strip away the boundary layer of air, which acts to insulate the object from heat transfer. The more you strip away the better. And the more you replace the air that was cooled by being in contact with the colder object, the better.

It isn't the air speed that effects the beans, it is the heat! After all, roasting is just a controlled burn of a cellulose material. Or, to put it another way. Imagine a very high speed airflow, but using ambient air. Nothing much is going to happen, right?

Until you get above the speed of sound I don't see airflow being a problem. Oh, how about a Mach 10 roaster? No heat needed, just the friction between air molecules and the beans. :)

 
http://www.intactamerica.org
seedlings
EddieDove wrote:
Hey Chad,

I sent you the files ... see if those work ...


Got em. Only problem is the physics-to-playground-talk converter didn't come through. Fortunately I have many prayers and one wing still on hand.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
seedlings
Dan wrote:
Until you get above the speed of sound I don't see airflow being a problem. Oh, how about a Mach 10 roaster? No heat needed, just the friction between air molecules and the beans. :)


Who has contacts in the Air Force? It'd be great to set up a picture of someone holding a long rod with a container on the end into the exhaust flow of an F-18, and then have a contest to put on a cliche roaster caption.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Chad, I was thinking more along the lines of re-entry speeds where air friction supplies all the heat! Anyone have contacts in NASA?
 
http://www.intactamerica.org
seedlings
I know first hand that Bill (bvwelch ) has some German rocket scientist contacts... perhaps... Bill?


On another hand, what about pressure cooked coffee?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
MarkBart
Oooo, how about we sneak into a KFC and pressure deep fry some beans?
I'm so Bad, I'm Good! www.homeroasters.org/php/images/smiley/cool.gif
I'm putting the small back into Small Business!
 
seedlings
MarkBart wrote:
Oooo, how about we sneak into a KFC and pressure deep fry some beans?


Heat the oil to 475 and letter rip!

I take mine with extra salt.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
cup_in_hand
Wow! A lot going on while I was gone!
Jim, wonderful work!s:1

I wanted to share some information from my conversations with Karl Shmidt from Probat.
I'm lazy so instead of diagrams I'm going to include his slide show again here.
I'll start with the fins on the lid. Air foils! As the air blows straight down into the bowl, through the beans, and up the sides, the fins direct the air back to the center to be sucked out the top.

Now about the concepts.
Probat wanted to build roasters using more convection heat, similar to a fluid bed roaster but without its drawbacks.
The drawback of a fluid bed roaster according to Probat is its limits on airflow,(to little air, the beans won't spout, too much air chaotic beans) and poor bean mixing.

Part of Probat's philosophy of roasting is that to get even roasting of the beans, you need to have even, controlled, mixing of the beans in the roaster.
Part of his presentation included video inside each type of roaster, that showed how long it took to mix the bean. Basically half way through a roast they added beans that had been dyed/ painted white so that you could see the beans mix.
The fluid bed never fully mixed, the drum roaster was better, followed by the tangential roaster ,and bowl roaster, with the Packed bed roaster mixing the coffee in a matter of seconds.
More on that later.

On to the thermodynamics:
For a frame of reference according to Probat the heat in their drum roasters is approximately :

80%convection
16-18% conduction
>2% radiation

Contrary to popular belief, little of the conduction heat comes from the drum itself, rather most of the conduction heat comes from the heat of the bean mass as it gets hot.

In drum roasters the ratio of convection heat to conduction heat is determined by the ratio of batch size to drum volume, as well as air volume and velocity. Hence these numbers will vary from manufacturer to manufacturer.

By contrast a fluid bed roaster is approximately 96% convection heat with the remainder conduction and radiant heat from the bean mass.
With conduction heat a more efficient method of heat transfer you get faster roasting times and bean development at lower temperatures.

On to the "bowl" roaster.
The concept of the bowl roaster is to get the convection ratio of a fluid bed roaster with more controlled mixing of the beans.
A bowl roaster uses 95% convection heat to roast the beans.
This is achieved by blowing hot air over and through the beans while they are mixing in a rotating bowl. The way the mixing was described to me was to picture putting ball bearings in a square frame on a moving conveyor belt. The bearing tumble over each other and move around but are more stationary relative to the bowl. Sort of like pulling a tablecloth out from under dishes.

If you look at the animation of the bowl roaster from the link and either add beans or click the "trace path" button, you will so the direction that the beans follow. This is the "Coriolis effect" that seedling described. The key to this seems to be the small cone in the center of the bowl. It forces the beans around it creating the path.

For cooling, when the beans are done the entire bowl lowers, spilling the beans over the side and into a cooling ring that surrounds the bowl. Very unusual.

The only downside to this roaster is heat sinking. It takes too long for the roaster to cool down enough to charge the next batch.

Packed Bed Roaster
Karl Schmitd seemed to take particular pride in this one when he described it.

Part of the confusion from the descriptions on whether the roasting chamber was stationary or not, is because the roasting chamber consists of an inner bucked shaped chamber with air louvers inside a stationary outer chamber. The inner chamber spins at a very high RPM forcing the beans against the wall in a "packed bed".(Jim was right on that score)

The air is blown tangentially around and through the roasting "bucket"from the opposite direction that the bucket spins.
This roaster uses almost 100% convection heat with even mixing.

As far as the bean mixing goes Dan's Gravitron analogy was right on. The beans move exactly the same way ,around the bucket, up the side and when they reach the top gravity drops them back into the center to start over.
In that video I mentioned earlier about the bean mixing experiment with the white beans, the mixing was almost instantaneous. I think I might like to try this experiment with my future roaster designs. It was very enlightening.
Heat sinking is not a problem with this roaster and he couldn't think of any problems.
I asked him why I had such a hard time finding information on this roaster and why its no longer on their website. He said they still make it and the market is primarily Asia and Europe. They made a temporary marketing decision to concentrate on promoting their newest bowl and tangential roasters.

I have more specifics but I have to pour over my notes.s:7
Edited by cup_in_hand on 05/07/2008 3:14 PM
Anton
A life without coffee is a life not worth living.
 
Brainiac
Well done Sherlock - sorry, Anton

Well, it appears as though the plot has thickened (if not exactly packed).

The spinning-bed roaster described in US Pat 5068979 and referred to earlier in this thread (stationary bucket) is quite different in operation to the Probat packed-bed roaster described by Anton (spinning bucket).

Intuitively it would seem that the Probat roaster would require less airflow and a simpler aperture design - maybe better for a home-roaster adaptation?

BTW, congratulations on your win s:2
 
dBndbit
Terrific info, Anton!!! That's a lot to think about. I'd love to see those videos. Please follow-up with any more info you might remember.

95%+ convection heating is complete different than any of what I've read before. And his comments on the relative mixing in drums vs. air-spout roasters changes some of my thinking as well. And I'm having trouble understanding the super-mixing if the beans are merely being slowed down at the rim to falling back over the rotating bed, not being scooped back toward the center in a little arc over the bed. Dang, I wish I could see the videos!!! I'm just going to have to do some experiments, no matter how much the neighbors want me to cut my grass.

Thanks much for the great details.

Farmroast, did you say your bowl rotates in your dream machine, not just the spinner rotates? I missed that entirely in looking at the photos. Sounds like you may have the world's only homebuilt centrifugal roaster! But no matter what it's called, with that bean action it's an impressive machine.
s:1
Edited by dBndbit on 05/08/2008 1:49 AM
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
seedlings
Anton, this is amazing! Whenever you have time to sit, remeber and type, please, please do! Here are some of my questions:

How "deep" is the bed of beans in the bowl roaster? In my mind they should at most be a few beans deep all the time. If they are much deeper, then conduction would take over. Plus, is there less friction at the bottom of the beans, at the bowl than there is at the top of the bean bed? This would be the opposite of a river flowing. In a river the topmost water flows the fastest. I'm still having trouble seeing how this method is the best for mixing the beans.

A fluid bed air roaster IS the most effecient at transferring heat, just not so good at mixing the beans. Interesting.

Great, GREAT stuff. We're so glad you're here!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Anton, Thanks SO MUCH for taking the time to gather that information and report back. s:1 You've clarified a lot if issues we've been discussion, and you got it straight from the horse's mouth, as they say.

How do the beans get dumped from the Packed Bed roaster?

I've used the painted bean trick, too. It really works and you can see what's going on in your roaster design. You only need to paint about 10% of the beans, not half. I pick them out and save them for next time.

The fins direct air? Oh joy. Grin

Brian, I agree, a spinning bucket (even thought it adds a motor and bearings) is simpler for DIY because you can use readily available perf metal.

Jim, It's my understanding that in the Packed Bed roaster the beans are also tumbling over each other as they crawl up the side of the bucket to fall back down. This would increase mixing.
 
http://www.intactamerica.org
farmroast
dBndbit wrote:

Farmroast, did you say your bowl rotates in your dream machine, not just the spinner rotates? I missed that entirely in looking at the photos. Sounds like you may have the world's only homebuilt centrifugal roaster! But no matter what it's called, with that bean action it's an impressive machine.
s:1
My theory is that the spinning bats at the bottom of the pot would hit the beans upward with a bit of a slice effect (like a golfing slice) due to the angle of contact. Like a right handed batter aiming for the left field green monster wall at Fenway park. The bats keep hitting/peeling the beans from the bottom upward and the beans on the top of the whirling mass lose momentum and drop to be batted up again producing the mixing effect with a spiraling motion. The speed control motor allows me to adjust bat speed with load size and speed of convection desired. The adjustable fan speed adjusts the power behind the convection air flow. I thought of spinning the pot but thought it was unnecessary with the amount of load. A matter of depth of bean mass compare to circumference of pot.I will try the white bean trick with my adjustable stroboscope to see what the mixing pattern looks like.
Congrads Anton s:2 s:2 s:1 and thanks for the info from Probat
farm
Edited by farmroast on 05/08/2008 4:49 AM
Ed B.
DreamRoast 1kg roaster, Levers, Hand Mills http://coffee-roa...gspot.com/
 
dBndbit
I suppose...

on the strength of the info from Probat/Karl Shmidt I'll have to accept that the curling vanes in the lid of the roaster photo are for air and not beans.

And I owe Dan a half-cup of cold coffee. He was right.

Does the post office have a tupperware flat rate box?

----------------------

But it sure is an amazing coincidence that the numbers show beans at the top of the bowl, hitting a small curling scoop just like in the picture, would make a perfect trajectory back to the bottom of the bowl in the hot air stream. So if I actually build one of these things, that's what MY curly vanes will do.

What's the good of having prejudices if you have to listen to a bunch of logic?
Edited by dBndbit on 05/09/2008 1:53 PM
Jim
11 years old... forever!
ReeferDoor.com
>home-built roasters and fair trade
 
http://www.ReeferDoor.com
Brainiac
Jim

Go with your prejudices, I say...

The "airfoils" are necessary to deflect the beans back to the bottom of the bowl - if they didn't, the beans would just smoosh (technical term ;) ) up against the junction of the rotating bowl and the stationary lid, and the centrifugal force would be assisted by the airflow in keeping the majority of the beans there - certainly not optimal mixing.

My (admittedly rudimentary) experiments with various bowl shapes at various speeds show that the beans need the "airfoils" (deflectors) to circulate, with or without forced airflow.

I believe that the deflectors are airfoil in shape because you need to treat the moving mass of beans as a fluid.

This is mind-expanding stuff!!

Brian
 
MarkBart
Just use the standard Tyvek postal envelopes and write Tupperware on the front. Be sure to address the labels before putting them on the envelope or you might cause leakage during shipment. Your mileage may vary.
Edited by MarkBart on 05/09/2008 9:16 PM
I'm so Bad, I'm Good! www.homeroasters.org/php/images/smiley/cool.gif
I'm putting the small back into Small Business!
 
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