Fluid Beds: Keep max loft
-
MNate
- Posts: 959
- Joined: 8 years ago
In today's Roast Magazine free webinar summit, Rob Hoos talked on airflow. He actually mentioned Fluid bed roasters quite a bit! Some relevant info he reported (if I have it right):
-keep airflow at maximum bean movement (but without it getting in the chaff collector)
-this evens out the heat transfer to all the beans, helping them roast consistently bean to bean
-this also prevents burnt tips because bean movement keeps the beans from getting stuck by the heat source
-modulate temp with just the heat setting
-however as you have to adjust the fan down throughout the roast, use some tricks to hide that drop... (what he talked about may have been more with drum roasters but I get the impression he would not have you raise the heat setting to offset the fan drop but might say to stagger the heat setting drop and the fan setting drop so the curve is more smooth...
-sure, your probe may be measuring more air temp than bean temp and so read higher, but he emphasized that probes are always measuring somewhat air and somewhat bean so you just live with the data you have in your machine.
He seemed to argue a bit that high airflow is not an enemy, it's not responsible for drying out beans, (that has more to do with relative humidity), and fluid bed roasters shouldn't be discounted because of it. Also that even in drum roasting much much more heat transfer happens through the air than through the metal so again, fluid bed setups aren't inherently worse here.
Well, it's certainly different than how I had been roasting on my SR800 but it may hold promise to fix my obvious mistakes and lack of good flavor in my results.
We shall see! Part of the problem may be just keeping the loft consistent. It may be easier to keep low than keep high.
-keep airflow at maximum bean movement (but without it getting in the chaff collector)
-this evens out the heat transfer to all the beans, helping them roast consistently bean to bean
-this also prevents burnt tips because bean movement keeps the beans from getting stuck by the heat source
-modulate temp with just the heat setting
-however as you have to adjust the fan down throughout the roast, use some tricks to hide that drop... (what he talked about may have been more with drum roasters but I get the impression he would not have you raise the heat setting to offset the fan drop but might say to stagger the heat setting drop and the fan setting drop so the curve is more smooth...
-sure, your probe may be measuring more air temp than bean temp and so read higher, but he emphasized that probes are always measuring somewhat air and somewhat bean so you just live with the data you have in your machine.
He seemed to argue a bit that high airflow is not an enemy, it's not responsible for drying out beans, (that has more to do with relative humidity), and fluid bed roasters shouldn't be discounted because of it. Also that even in drum roasting much much more heat transfer happens through the air than through the metal so again, fluid bed setups aren't inherently worse here.
Well, it's certainly different than how I had been roasting on my SR800 but it may hold promise to fix my obvious mistakes and lack of good flavor in my results.
We shall see! Part of the problem may be just keeping the loft consistent. It may be easier to keep low than keep high.
-
hercdeisel
- Posts: 160
- Joined: 5 years ago
Oh interesting! Thanks for sharing.
I think it might matter a lot what the baseline bean movement/air flow of a set up is.
The difference in bean movement for me with the SR800 and the stock tube and the 9.5" razzo is (as you know) wildly different. With the stock tube the beans do that putt putt chuff chuff movement where they sort of shoot up the middle and work their way down and that movement pattern speeds up a bit but the same movement pattern lasts well into the roast. With the razzo even when I first add the beans to the roaster they roll in a continuous circular motion in the chamber. I've never had any issues with tipping with the razzo, that's for sure.
From my set up I definitely find I can get a more baked/flat flavor profile when I keep the fan higher and try to use primarily heat setting. That produces a *lot* of movement.
So, some of this may be a matter of 'what is your baseline air flow/bean movement' setup since different setups can produce pretty radically different air flow.
This is super interesting stuff though. I'm happy to hear there are some serious investigations being made into fluid beds!
I think it might matter a lot what the baseline bean movement/air flow of a set up is.
The difference in bean movement for me with the SR800 and the stock tube and the 9.5" razzo is (as you know) wildly different. With the stock tube the beans do that putt putt chuff chuff movement where they sort of shoot up the middle and work their way down and that movement pattern speeds up a bit but the same movement pattern lasts well into the roast. With the razzo even when I first add the beans to the roaster they roll in a continuous circular motion in the chamber. I've never had any issues with tipping with the razzo, that's for sure.
From my set up I definitely find I can get a more baked/flat flavor profile when I keep the fan higher and try to use primarily heat setting. That produces a *lot* of movement.
So, some of this may be a matter of 'what is your baseline air flow/bean movement' setup since different setups can produce pretty radically different air flow.
I think this is spot on. I've noticed I can get far more lively, brighter roasts by keeping my bean rotation constant and smooth but with as low a fan setting as possible (although I've also found that roasts with similar development times with lower fan settings end up darker than with higher fan settings, so for similar overall development I've been shortening roast times a bit). The flow is still constant and smooth rolling but it isn't a super high roll.MNate wrote:Part of the problem may be just keeping the loft consistent. It may be easier to keep low than keep high.
This is super interesting stuff though. I'm happy to hear there are some serious investigations being made into fluid beds!
-
hercdeisel
- Posts: 160
- Joined: 5 years ago
These videos are available on the Roast Magazine youtube channel now. Here's the airflow talk:
