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snwcmpr
08/20/2019 3:47 PM
Roasted the last of the SM Kenya Nyeri Katogoto this morning.

snwcmpr
08/20/2019 3:47 PM
So, Allen gets notification. 'renatoa' gets notification. ... I do not. Funny stuff. But not earth shattering.

snwcmpr
08/20/2019 2:01 PM
PM sent

allenb
08/20/2019 10:32 AM
snwcmpr, send me a pm so can see if I'm getting email notifications now. Thx.

snwcmpr
08/18/2019 4:31 AM
Awesome I sent an email to AllenB and JackH The email to JackH failed. I had screenshots of my settings.

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CoffeeAir II Roaster Build
seedlings
Here are a few pictures... I had to get the square peg (heat tube) to fit the round hole (blower outlet).

i206.photobucket.com/albums/bb54/seedlings/13coffeeairii51.jpg
i206.photobucket.com/albums/bb54/seedlings/13coffeiarii52.jpg
i206.photobucket.com/albums/bb54/seedlings/13coffeeairii53.jpg
i206.photobucket.com/albums/bb54/seedlings/13coffeeairii54.jpg
i206.photobucket.com/albums/bb54/seedlings/13coffeeairii55.jpg

The elements will fit in this tube, and each element came with 2 sheets of mica:
i206.photobucket.com/albums/bb54/seedlings/13coffeeairii56.jpg

I'm waiting to get the hopper back from a coworker doing some welding. Once the hopper is here, I will jigsaw puzzle some contraption together to join the heat tube to the hopper.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
JETROASTER
Hi Chad,
This looks like a fun one. If that Kirby is old enough to have a metal fan, it could handle a small amount of recirc.
Most of those also had a high speed option built into the safety switch(front of fan housing).
Looking forward to your progress. Scott
 
seedlings
freshbeans wrote:
Hi Chad,
This looks like a fun one. If that Kirby is old enough to have a metal fan, it could handle a small amount of recirc.
Most of those also had a high speed option built into the safety switch(front of fan housing).
Looking forward to your progress. Scott


My previous attempt included recirculation, but I didn't have enough electric heat. I hoped to roast 2 pounds with 1800W element + recirculation. After reading more, I think my air-to-nichrome heat transfer was grossly inefficient. I did keep the recirc temps around 200F and the kirby just kept going. It really is a beast. There's even a heatslinger between the motor and the fan.

http://forum.home...post_10094

CHAD
Edited by seedlings on 05/05/2010 4:44 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
JETROASTER
Yup, that's good ol' fashioned American quality.
Rebuilding all these vacuum motors is just part of the daily grind for me. If you need parts, drop a line. Scott
 
bvwelch
CHAD - way to go! we're watching this project closely! I love the idea of using cement board too.

Possibly stupid idea-- connect a hose or some such to move the noisy motor further away from the entire setup?
 
endlesscycles
seedlings wrote:
... After reading more, I think my air-to-nichrome heat transfer was grossly inefficient. ...
CHAD


That sort of inefficiency doesn't exist.

temperature increase = heating power / airflow

It really is that simple. Either increase the power or decrease the airflow.
-Marshall Hance
Asheville, NC
 
seedlings
bvwelch wrote:
CHAD - way to go! we're watching this project closely! I love the idea of using cement board too.

Possibly stupid idea-- connect a hose or some such to move the noisy motor further away from the entire setup?


I've read that the longer distance between the blower and coffee, the more "bounce" the beans have (bouncing on the cushion of air), instead of a steady flow... My sound isolation plan is mass (cement board) and insulation. If it's too loud, add more mass because the three things that are sure to stop sound (at a given distance) are mass, mass and mass.

Marshall, I understand what you're saying. I have more KW this time around, but I thought the area of the heat surface was in the equation: http://www.engine...d_430.html

CHAD
Edited by seedlings on 05/05/2010 7:02 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
bvwelch
seedlings wrote:
I've read that the longer distance between the blower and coffee, the more "bounce" the beans have (bouncing on the cushion of air), instead of a steady flow...
CHAD


Any links to this info online?

Will your air be blasting thru a perf-plate before it strikes the beans anyway? Seems like that would mask just about everything below it... -bill
 
endlesscycles
100% of the energy leaves the element. Otherwise, it doesn't exist. First law of thermodynamics. Almost all of the heat energy goes up with the air regardless of layout, though some energy does radiate through the duct. If you are lucky, a lot of that energy goes into into the beans. That particular efficiency is determined by your roast chamber design and construction and is governed by the equations you link to.
For heating the air, it is simply:

temperature increase = heating power / airflow

In other words, it doesn't matter so long as the heating element is both on and in there.
-Marshall Hance
Asheville, NC
 
RoasterRob
I get the bounce toward the end of the roast when the air flow is dialed down. I believe Wes had some issues with it. He had the 2 VC blowers in another room and a longer or larger volume air path. The perf plate isolates it up to a point, in my case when the air is dialed down. Don't always get it, and don't get it when I roast 2.1kg or less.

Rob
Edited by RoasterRob on 05/05/2010 8:32 AM
VBM Minimax 2gp, 1gp Reneka Techno, 2 gp la Pavoni Pub, la Cimbali M28, SJ Maz, FB 6kg HM roaster and other stuff
 
bvwelch
Thanks Rob, that's good enough for me-- I will remember to keep the blower very close to the roast chamber.
 
allenb
seedlings wrote:

Marshall, I understand what you're saying. I have more KW this time around, but I thought the area of the heat surface was in the equation: http://www.engine...d_430.html

CHAD


Engineeringtoolbox.com you reference spells out clearly the other variables that do play into heat transfer efficiency of any heat exchanger system in addition to watts and cfm. Surface area of element and location within the air stream are just as important as power/cfm. If it weren't you could throw in any stovetop tubular heating element in the airstream for a 1/4 lb batch size roaster and achieve 500+ F. Wouldn't life be simpler!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
endlesscycles
allenb wrote:
...If it weren't you could throw in any stovetop tubular heating element in the airstream for a 1/4 lb batch size roaster and achieve 500+ F. Wouldn't life be simpler!

Allen



You absolutely could use a stovetop element. They are [email protected], which at 15cfm raises the air temperature by 400F. With the right blower motor and perforated plate design, you could build a fine 1/2lb roaster.

Consider that you are misleading and possibly discouraging some would be inventors out there.
-Marshall Hance
Asheville, NC
 
allenb
If anyone in this forum happens to take the time to throw a stovetop element into a duct and with 15 cfm of normal ambient room temp air flowing across it achieves an air temp high enough to complete a roast (past C1 in less than an hour), I will formally revise my statements concerning heat transfer efficiency.

Otherwise, I feel my last post is preventing the misleading of potential builders/inventors.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
endlesscycles
lh4.ggpht.com/_TqlH8Gwf4Xo/SdT4pshZicI/AAAAAAAADYY/ygRbqRfSByc/s640/IMGP0484.JPG


Temperature increase = Heating power / Airflow
-Marshall Hance
Asheville, NC
 
Koffee Kosmo
So
That's where the saying came from
"There is more than one way to skin a cat"

KK
I home roast and I like it
Blog - http://koffeekosm...gspot.com/
Bezzera Strega: Mazzer Robur Grinder: 5 Box hand grinders: Pullman Tamper Convex: (KKTO) Turbo Oven Home Roaster: CONA Glass Rod Syphon: Pyrex Brewer:
 
http://koffeekosmo.com.au
seedlings
Brilliant! Marshall, I won't [shouldn't] say another word. ThumbsUp

But I will ask the relationship between hot airflow and roasting beans. Is there an equation, or is experience the key? As an example, if that electric stove burner sample roaster were 10" off the burner instead of 2", how/why does that change how fast the coffee roasts?

CHAD
Edited by seedlings on 05/06/2010 2:06 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
endlesscycles
Thermodynamics of a bean are not so simple. My basic theory is to get the inside hot without a decrease in temperature from the rest of the bean. With that said, I think there is a problem with very deep bed air roaster designs in that the loss of temperature waiting for a convective pulse causes some flattening in the cup.

Here are some variables that come into play with your burner/distance question:

10" away: More roaster material to both retain and loose heat energy through. More even heat distribution at the drum. Longer lag time from heat adjustments.

2": away: Fast reaction to adjustments, possible hot spots, on drum. More system efficiency.

Obviously you want enough distance to even out heat distribution, maybe to temper sudden changes in output via mass of both roaster and air, and to reduce roaster inefficiency due to losses through the walls. For well insulated devices, the energy requirements are constant., but the larger one might need more warm up time.
-Marshall Hance
Asheville, NC
 
allenb
Alright, I grudgingly have to eat some crow here. Marshall's stating of basic thermodynamics (watts from an element have to end up being absorbed into the air stream) are fact and has to be applied to any forced air convection heater.

In doing further research it appears the only reason for going through the brain damage of calculating coefficients of efficiency etc... is to ensure sufficient heat exchange to avoid premature burnout from elevated element temperatures.

As Marshall stated earlier, the only reason a convection heating system may not raise the air temp sufficiently will be due to losses via conduction through uninsulated exchanger enclosure walls or radiant transfer to and through uninsulated walls. Otherwise, watts in-heat out.

I, unfortunately have built more than my share of poorly designed convection air heaters that wouldn't get it done and didn't realize it was due to losses and not perfect nichrome coil placement and spacing.

Unta and Seedlings, my apology if my statements caused any unnecessary changes in your convection heater design strategy.

Marshall, my apology for an inappropriate tone and sarcasm in my posts. Especially when my points are invalid.

Keep us honest and accurate!

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
seedlings
You and me both, Allen.

So, this means I can put the two heat elements side-by-side instead of inline and there will be little to no effect on heat (if the cement board does it's job to help prevent loss), which will make for a more compact design, and easier to install/replace elements.

CHAD
Edited by seedlings on 05/07/2010 7:29 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
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