"Nonexistence of Heat Momentum" - Page 3

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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EddyQ
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#21: Post by EddyQ »

Almico wrote:Exactly, but my query is why the RoR would increase (significantly) almost 2 minutes after the burner has been shut off.
You have a piping hot drum. After FC while your bean has less water (thermal mass) leaving a cellulose insulating blanket. No need for gas or flames.
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HoldTheOnions
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#22: Post by HoldTheOnions »

Almico wrote:Exactly, but my query is why the RoR would increase (significantly) almost 2 minutes after the burner has been shut off.

Next time I do a darkish roast, I'll record the screen.
Curious what roaster you are using.

Marcelnl
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#23: Post by Marcelnl »

crunchybean wrote:I dont understand this, real observations are still based on that one person's machine, setup, environment, etc... you and Almico both have conflicting data. Secondly, all those "physics" equations are chemistry equations...
To me it seems more like a combination of chemistry and physics, perhaps looking at data from an empty roaster or a roaster filled with a load of beads with known thermal properties helps isolate the effect of the beans a bit. Sounds like a PhD thesis for someone to me.
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Almico
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#24: Post by Almico »

HoldTheOnions wrote:Curious what roaster you are using.
It's a 5kg typical Turkish roaster. Mild steel drum, 1/2" thick cast iron faceplate etc. Fixed speed drum and air. I control airflow with a damper on the exhaust tube.


crunchybean
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#25: Post by crunchybean »

Marcelnl wrote:To me it seems more like a combination of chemistry and physics, perhaps looking at data from an empty roaster or a roaster filled with a load of beads with known thermal properties helps isolate the effect of the beans a bit. Sounds like a PhD thesis for someone to me.
Yes it is a combination of sciences, the proper word is thermodynamics, a branch of physics. But just like the use of "exothermic", like coffee beans, people do not want to change..that was a bad physics joke.

HoldTheOnions
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#26: Post by HoldTheOnions »

Almico wrote:It's a 5kg typical Turkish roaster. Mild steel drum, 1/2" thick cast iron faceplate etc. Fixed speed drum and air. I control airflow with a damper on the exhaust tube.

image
Yeah, that's a serious roaster, I have no relevant comment for that :wink: ROR increasing 2 minutes after turning off burner does sound really weird to me though.

false1001
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#27: Post by false1001 »

Maybe i'm just being slow here, but steam pressure rupturing pockets of cellulose is an exothermic reaction, no?

I do agree that the idea of the beans entering some sort of exothermic "phase" between 1C and 2C is a little absurd, but the actual moment of a bean hitting 1C has to be exothermic... right?

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EddyQ
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#28: Post by EddyQ »

false1001 wrote:Maybe i'm just being slow here, but steam pressure rupturing pockets of cellulose is an exothermic reaction, no?
Absolutely not.
false1001 wrote:I do agree that the idea of the beans entering some sort of exothermic "phase" between 1C and 2C is a little absurd, but the actual moment of a bean hitting 1C has to be exothermic... right?
No. Exothermic means the medium is generating its own heat. If a material is exothermic, you could pour it into an insulated container and the temperature would rise and eventually catch fire.

At first crack, the bean is rupturing with release of water pressure. And since the pressure in the bean suddenly drops, there is just the opposite of an exothermic reaction going on. Energy is lost and temperature drops.
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Bret
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#29: Post by Bret »

My first college class (many many years ago) was chemistry. One morning the professor snipped half the length of his necktie off with scissors. "This is a physical change," he announced.

He took the cut piece and lit it on fire. "That is a chemical change."

"My wife gives me a new tie every Christmas. This is what I use it for...."

I don't remember much chemistry, but I do remember him.

Rush
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#30: Post by Rush »

HoldTheOnions wrote:Yeah, that's a serious roaster, I have no relevant comment for that :wink: ROR increasing 2 minutes after turning off burner does sound really weird to me though.
Oh man, if I do things perfectly (wrong), I can get ror to rise after 1C crash for 3-4 minutes with zero heat being applied to the coils on my 1kg electric drum roaster.