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Topic: Graph of exothermic evidence (26 msgs / 640 lines)
1) From: Ed Needham
Barry's graph showing possible evidence of an exothermic bean reaction is
up...http://www.homeroaster.com/exotherm.htmlI'm sure more experiments could refine the results and isolate extraneous
variables, but this is pretty neat!
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
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2) From: Jim Schulman
On 23 Jan 2003 at 23:32, Ed Needham wrote:
<Snip>
It is neat; but I'm avoiding any experiments that 
take my beans to 520F! Wasn't the fire a give away 
;)
Jim Schulman
<Snip>
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3) From: Mike McGinness
From: "Jim Schulman" 
<Snip>
I don't know, I don't think I've every pushed it beyond about 480f. Might
be *fun* to see what happens! (I'm am a pyro at heart after all, just
remember to duck on the 4th of July:)
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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4) From: Oaxaca Charlie
--- Mike McGinness  wrote:
<Snip>
 If you push the bean temp over 600F you'll get your fun. It
helps to cut off the airsupply to build up combustable gases if
you really want an impressive bonfire-something hard to do in a
hotair roaster, too bad.;o) If Barry had left the heat supply on
a while longer and then turned on the air a fire that would take
several fire extinguishers(at least) to put out would have
erupted.(Barry knows that) Very high ignition temp, but coffee
oil burns like kerosine only hotter.  I'm glad I discovered this
interesting fact using an outdoor roaster with a water hose
handy and no burnable or meltable parts on my roaster. To see
some pics of the unmeltable roaster go to Ed's homeroaster.com
site . Ed put some new pics there and I promised to mention it. 
Charlie
<Snip>
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5) From: Jim Schulman
On 23 Jan 2003 at 23:30, Oaxaca Charlie wrote:
<Snip>
I can see it now: "How to the build a tandoori or 
pizza oven roaster -- after all, anything under 
800F is underroasted"
Jim
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6) From: Ken Mary
<Snip>
Equally as important is the point at 12.5 minutes where the graph suddenly
begins to deviate from the normal gentle curve. The rise becomes less steep
indicating that some reactions are consuming heat. This is the first crack
"endotherm" where the beans require more heat. Failure to supply enough heat
at this point may let the bean temperature fall out of the reaction zone and
may lead to baked flavor. Then at 14.5 minutes the slope becomes greater
than that of the earlier (heatup) portion of the curve indicating that the
"exotherm" begins here.
--
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7) From: Paul Furuta
<Snip>
Yes, if you take the 1st derivative of the curve, it would show the rate of 
change in the slope, giving a clearer veiw of the endotherm and exotherm 
(like a DSC).
Paul
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8) From: Dan Bollinger
<Snip>
steep
<Snip>
heat
<Snip>
and
<Snip>
That's how I read the curve, too.  This matches the curve in the Hobbie &
Eggers article, btw.  Dan
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9) From: AlChemist John
Sometime around 05:17 1/24/2003, Dan Bollinger typed:
<Snip>
I am NOT (I say NOT AGAIN) saying it does not prove exotherm...It may be 
worth noting that the bean temperature never rises past the high point of 
the input temperature.  That would truly prove an exothermic reaction.  I 
think this is just heavily circumstantial evidence (although very good 
data, and indicative of the system being exothermic)
--
John Nanci 
AlChemist at large
Roasting and Blending by Gestalt
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10) From: Jim Gundlach
A very interesting graph.  Based on some of the previous discussion I 
had moved from an exothermic doubter to generally believing that there 
was an exothermic reaction.  This graph moves me back into the doubter 
camp.  Briefly, here is why.  If you note the two lines from about 3.5 
to 12.5 minutes you see that the temperature of the drum air and the 
beans are increasing at about the same rate, that is both lines are 
straight but not parallel.   This is quite reasonable given the 
constant input of heat with the gas burner set on high.  Then soon 
after 12.5 minutes, the rate of increase in bean temperature slows 
down.  Here, as the beans approach the second crack, something is going 
on to cause a reduction in the rate of transfer of heat from the drum 
air to the beans.  Could this be related to the sheen?  Around this 
point the slope of the line showing the temperature of the drum air 
starts to take a slightly steeper slope.  If I understand the argument, 
this steeper slope is considered evidence for exothermic reaction.  I 
would interpret it somewhat differently.  Given the constant addition 
of heat from the burner to the air and a reduction in the rate of heat 
transfer from air to beans, you would expect the slope to increase just 
because the air is not getting rid of the heat as fast as it was 
earlier.  Hope this makes sense.
Jim Gundlach
On Thursday, January 23, 2003, at 10:32 PM, Ed Needham wrote:
<Snip>
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11) From: Marchiori, Alan
Consider that the heat is shut off at about 16 minutes, yet the bean temp
rises 50 degress from 16 minutes - 18 minutes, without external heat being
applied.  I guess the exothemic camp is saying the beans heated themselves
these exta 50 degrees.
alan...

12) From: Ed Needham
He told me it was just an experiment.  No intention of actually using the
very dark charbeans.
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
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13) From: Ed Needham
Maybe old coffee beans could be substituted for the standard pellets in the
Traeger .
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
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14) From: Ken Mary
<Snip>
Thinking about it some more, I wonder why the slope of air temp increases at
about 12 minutes. Then, we are speaking as if what we see on the graph is
what really happened. From a chemical engineering perspective, I do not like
the smooth curves and slow response to the bean addition. This shows a delay
in measurement from temp probes with large thermal inertia. Maybe the slope
changes are artifacts of the measurement process. A big unknown is the drum
metal temp. Maybe we (myself included) are grasping at straws trying to find
evidence that suits our own preconceived notions.
--
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15) From: steve_w
Quoting Ken Mary :
<Snip>
I think that a careful study of the beginning temperature readings is most
instructive.  If I am interpreting the graph right the drum was preheated,
then a batch of beans at ambient temperature is dumped into the drum at T=0.
The "bean temperature" probe starts at 390 degrees and drops down to 200 F in
just under 3 minutes.  Now, assuming that the beans really were at room
temperature at T=0 then the bean mass probe is giving a wildly false reading
for at least the first 2 minutes, indicating a bunch of thermal mass in the
probe.  This makes me doubt the bean temperature readings throughout.
The temperature lag from drum air to bean mass probe could be significantly
effected by the thermal inertia of the bean mass probe, and the dip and
rise in bean temp rate increases in the 1st and 2nd crack region could
be time lagged severely.  And this is the roaster we're holding up as
a model for the home roaster?
Steve Wall
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16) From: Oaxaca Charlie
--- Ed Needham  wrote:
<Snip>
 They're being used to fire power plants in Brazil. The "coals"
left after 5 lbs of beans burned in my basket for a while before
being put out with lots of water were dumped on a pile of wet
wood being saved for a summer bonfire. An hour later that pile
of stumps and knotty wood went up in flames. Is Vietnamese Blue
Cloud cheaper than wood pellets???Hmmmm.
Charlie
<Snip>
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17) From: Mike McGinness
From: "Oaxaca Charlie" 
<Snip>
 Is Vietnamese Blue
<Snip>
Oh my god!!!! The SMELLLLLLLLLLLLLLLLLLLLLLLLLLLLLL ARRRGGGHHHHH
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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18) From: Mike McGinness
From: "Ed Needham" 
<Snip>
Oh sure, he really sold them to Charbucks!
MM;-) aka Kona Konnaisseur miKe mcKoffee
Dual Variable Transformer Rosto Roasting
Rocky grindin' - Miss Silvia brewin'
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19) From: john kangas
<Snip>
But maybe a Kona-fueled smoker? Mmmm, kona-smoked turkey/beef/pork...
I'd have to agree on the Vietnamese beans, I'd probably rate that a few 
steps below a dried cowpatty smoker.
John
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20) From: Les & Becky
Well, we are back on the endothermic vs. exothermic thread again.  I didn't
want to post what I am going to say in fear that it would begin again, but
now I have no fear as it has begun again!  Because of the intense discussion
on the group, and my son reading all the great posts on endo vs. exo, he got
an A on his chemistry test due to an in-depth understanding of the two
concepts!  Personally, if the coffee tastes good that is all I care about.
I saw an ultra cool graph of coffee compounds at Alchemist John's place of
employ from his phenol experiments.  That was worth it, and he let me smell
the pure essence of coffee after it had be run through his super extraction
machine.  It would make a great potpourri!
Les
Roasting and Turning tampers in S. Oregon
www.thortamper.com

21) From: Ed Needham
Since Barry Jarrett is not on this list, I am posting a response from him
concerning the graph...
Please send him an email of any replies to this post.
barry
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
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 >If I am interpreting the graph right the drum was preheated,
 >then a batch of beans at ambient temperature is dumped into the drum at
T=0.
 >The "bean temperature" probe starts at 390 degrees and drops down to 200 F
in
 >just under 3 minutes.  Now, assuming that the beans really were at room
 >temperature at T=0 then the bean mass probe is giving a wildly false
reading
 >for at least the first 2 minutes, indicating a bunch of thermal mass in the
 >probe.  This makes me doubt the bean temperature readings throughout.
Barry's response:
Uh...  no.  The thermal mass and inertia of the bean mass far outstrips that
of the probe (1/4" diameter stainless sheath,
grounded junction, no thermowell).  If you look at the initial slope of the
bean temp curve, you'll see that if it were
extended downward, the bean temp would be below 200F in well under 1 minute
absent further energy inputs.   Realize
the bean probe measures a mixture of drum air and bean temp, as the mass of
beans is constantly being mixed, and that
the heater is on.  There is convective, conductive, and radiant heat.  The
bean probe isn't going to plummet immediately
to room temperature because of the energy in the drum which is being mixed
with the beans.  The bottoming out of the
graph at about 2:45 is the 'turning point' of the roast, and represents the
point at which the system has overcome the
thermal drain of the bean charge and everything begins to heat up.  This is
not an overpowered air roaster doing 1/4lb
batches;  this is an underpowered drum roaster doing 12lbs at a time.  Things
do not happen quickly.
If it would help alleviate your doubts, I'd be happy to datalog some probe
excursions into cups of hot and cold water, so
you can see that the probe really *does* respond in a decent timeframe.
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22) From: Ed Needham
It's really a cool concept if we can keep our brains connected to the
keyboard.  I hope it can be an intelligent discussion, and not a cowboy
shootout.
Ed Needham
To Absurdity and Beyond!http://www.homeroaster.comed
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23) From: Ben Treichel
The thing that wasn't clear to me is if the fan was still running at its 
normal speed with the gas off. I'm just looking to see if there was a 
difference in bean/air movement past the probe after the heat was turned 
off.
Ben
Ed Needham wrote:
<Snip>
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24) From: Dan Bollinger
I don't understand why it would begin again. I thought the consensus was
that coffee roasting did enter an exothermic stage during normal roasting.
All of the evidence points that way and if you recall, there were numerous
references to scientific articles agreeing including the Hobbie and Eggers
articles.  Dan
<Snip>
didn't
<Snip>
discussion
<Snip>
got
<Snip>
smell
<Snip>
extraction
<Snip>
addition
<Snip>
heat
<Snip>
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25) From: Steve Wall
On Saturday, January 25, 2003, at 01:03 PM, Ed Needham wrote:
<Snip>
I don't think it'll be necessary.  You would expect water to transfer 
heat
to or from your probe much faster than a pile of cold or hot beans.  Or 
cold
beans mixed with hot air which, as Barry says, is probably what the 
bean mass
probe is sitting in for the first few minutes.  I'm curious about the 
location
of the bean mass probe though.  Does it sit deep in the beans from the 
start
or do they need to expand a bit to fully cover it?
It'd also be interesting to have a reading of the drum temperature 
throughout.
I think that a drum that is still hot could explain a lot of the heat 
rise in
the bean mass after the gas is cut off.
Steve Wall
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26) From: Oaxaca Charlie
<Snip>
 And an other idea that was kicked around was that the heat
inside the beans just started coming out and raised the temp
around them...
Charlie
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