General question about BT ROR - Page 3

#21: Post by **Felice** » December 23rd, 2017, 12:27 pm

So, in order for the beans to become exothermic, wouldn't they have to be hotter than the drum temp? I'm not clear on how the beans could be releasing heat against a gradient. Is that possible? I've always thought the rapid increase in temps after a perceived crash was a combination of the thermocouple catching up after the misreading around the crash, coupled with the beans being lighter in weight as well as darker in color.

#22: Post by **btreichel** » December 23rd, 2017, 11:26 pm

Nope, just means that the reactions in the bean are generating heat.

#23: Post by **drgary** » December 24th, 2017, 2:07 am

Sum up the heat already in the beans and in the roasting chamber and the heat being generated through chemical changes in the bean and heat can climb quickly to the point where turning off the heating source doesn't stop a rapid rise and you may need to blast the fan to keep it under control.

#24: Post by **drgary** » December 24th, 2017, 3:39 am

Back to driving through 1C, or not ..., I found this useful note from my friend, Henry Chang, in a 2014 thread,

Drum Speed: The physics, convection and conduction debated

chang00 wrote:For me and in my roaster, the most important equilibrium point is at first crack. If I aim for the "Nordic" roast like ~<1c/min rate of rise of the "bean mass temperature", I need to know the equilibrium point where the gas and damper opening gives a flat temperature curve at given green coffee charge weight. If I aim for 5c/min (my basic roast), I set the damper and gas setting for a slightly steeper rise, in which the damper is slightly more closed (less air flow) than the "Nordic" setting.

At charge temperature, the damper generally is closed, because the drum is transferring heat energy to the beans and I don't want to loose that energy.

This gets me back to Dave Borton's frequent reminder to cup and then cup some more.