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Energy to raise coffee bean temp?
endlesscycles
Is there a handy resource to determine the joules required to raise the temperature of, say, 1lb of coffee by 400F? This is of course assuming 100% efficiency / no losses.
-Marshall Hance
Asheville, NC
 
SteveN
I don't know... anyone have a calorimeter handy?

Is this a question for scaling heat requirements or purely academic?
 
endlesscycles
I'm contemplating a 20lb closed system bubble bed roaster with cyclone and electrostatic precipitator to clean the exhaust. There will be heat losses, but I'm pretty sure the energy requirements before losses and getting to 300F in 3minutes will be on the order of 5kW. In other words, very efficient.
-Marshall Hance
Asheville, NC
 
SteveN
I pulled the following reference:

Journal of Food Engineering
Volume 78, Issue 4, February 2007, Pages 1141-1148
Analysis of the heat and mass transfer during coffee batch roasting

They used 2.41 kJ/kg*degreeC for the specific heat capacity. Let me know if you'd like the paper.
 
endlesscycles
That's all I'll need. Thank you so much!
-Marshall Hance
Asheville, NC
 
scarter11
Actually, that sounds kinda interesting. I'd like it if it's not too much trouble...
 
endlesscycles
This got me half way to making sense of those units: http://www.wolfra...tt+minutes
-Marshall Hance
Asheville, NC
 
SteveN
for everyone else... 1 J (joule) = 1 W (watt) * s (second)

So

1 kg of coffee needs 2410W of energy to raise the temperature by 1 degree C every second.
 
Dan
The curious thing about small roasters is that the energy going into the beans is much less than the energy being lost to the environment. You should be asking how to calculate heat loss. What I've found is that the amount of heat to roast, say, 1/2 kilo versus 1 kilo, in the same roaster is just about the same.
 
SteveN
For an air roaster I might calculate the amount of energy you will need to heat the air (at a particular CFM). Sure there are complicating factors, but wouldn't that be enough?
 
seedlings
This will be helpful:

http://www.aseanf...017334.pdf

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Dan
Steve, that's a good point. It is the air that is being 'roasted' first. The beans just go along for the ride. Any heat they don't pick up is going up the spout.

To heat air, 0.018 BTU/cubic foot/?F
 
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