[professional coffee roasting] effect of barrel speed on roasting temperature and time of coffee beans

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It's a very interesting discussion about barrel speed, especially when two masters say the opposite.

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For those of you who can adjust the drum speed. I know Rao is suggesting increasing speed toward the end of the roast but Boot suggest to decrease the speed at the end of the roast. Anybody tried the different options and found any difference?

Scott Rao recommends increasing the drum speed before the end of the baking, but Willem Boot says to reduce the speed before the end of the baking. if your machine is adjustable, do you have any other ideas or find that adjusting the speed has any difference in the baking results?

Boldjava (who has a deep relationship with Mill City, which is consistent with what Mill City said in the film) believes that the volume of beans during baking will increase by 35% and 45%, and he will increase the speed before finishing the baking to reduce the contact time between beans and rolling buckets.

Most people do not agree with lowering the speed at the end of the baking, because the purpose of increasing the speed is to increase the effect of hot air in the barrel and reduce the effect of barrel temperature on beans, while Willem Boot believes that slowing down the speed will slow down the heat transfer of the reasoning behind decreasing the drum speed later in the roast appears to be to slow down the transfer of heat (i.e.reduce convection) (video: https://coffeecourses.com/coffee-roaster-drum-design/) (for example, reduce the effect of convective heat)

People who bake beans feel that what they say is correct, because the general saying is that the semi-hot fan of the general single-layer pot body is used, and the temperature of the pot body is quite high, so it is reasonable to pull up the hot air at the end of the baking period to reduce the contact heat of the barrel temperature, and to increase the drum speed. The Willem Boot uses Giesen W6A, which is not only a double-layer pot body, but also conducive to heating hot air, so it is reasonable to reduce the rotational speed of the drum at the end of baking and reduce the effect of hot air on heat transfer.

What is most surprising is that the operating guidelines of a dryer indicate that "use low speed for high soybean quantity and high speed for low soybean quantity]. It does not consider the effect of rotational speed on baking, but when using low soybean quantity, if the rotational speed is too low, the beans will not be able to sample too low. it also makes sense.

What does the above tell us? Many masters' famous quotes have his truth, but they also have his background, and the result of taking them out of context is that their heads are knotted.

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