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Hybrid Build w/ Ceramic Band Heater
CharcoalRoaster
Is it possible to utilize a fluidized bed for agitation of bean mass with a more gentle heat application?

I came across some ceramic heating bands and it got me thinking. Would it be an effective roasting method to have the lower portion of the RC heated by the band heater conducting the heat to the bean mass while the forced air agitates? Or would it be problematic as some beans would have more contact with the walls of the RC than others resulting in uneven heat distribution?

Anyway, I'm mostly curious about potential uses for a ceramic band heater as I haven't come across their use in any previous build threads.
renatoa
So you are talking about contact or IR heat transfer ? Not sure I understand where will be the ceramic bands placed, inside the glass chamber or outside ?
What is temperature these bands are supposed to be able to radiate ?
Edited by renatoa on 12/28/2019 1:53 PM
CharcoalRoaster
So here's a really rough sketch of what I was imagining in my mind.

Their used for injection molding and the ones I've seen are 240v @ 2000w or higher with some specs saying up to 1200*F

https://www.dropb...d.jpg?dl=0
renatoa
How I see this sketch, at first sight seems ceramic band should help more for minimising heat losses, than adding some heat, because IR action is as light, heats is where is line of sight, so maximum two bean layers near the wall deep, not more, because the inner beans will be in the shadow of other beans. So, could help decrease the hot air temperature, but not much.

At second sight... conversely, I am wondering about worse..., the layer near the glass wall has a lot less agitation than the inner core of fountain, so I wonder if this approach would not led to uneven "tan", because a bean that slides down on the wall usually does not rotate during descending, expose to the glass a single side all the way down. And this side will get the whole hit of IR.

For those wondering about other transfer ways, IR passing a borosilicate glass does nothing, does not heat the glass body, so no increase in contact transfer, or convection from glass to air.
CharcoalRoaster

Quote

renatoa wrote:For those wondering about other transfer ways, IR passing a borosilicate glass does nothing, does not heat the glass body, so no increase in contact transfer, or convection from glass to air.


Yes, which is why I would only have the heat band around the metal portion of the RC. So the RC would be conjoined steel + glass (I have an extra bake-a-around at the house) or all steel. I was thinking the heat transfer wouldn't be infrared but more like conduction in a drum roaster, i.e. heating band applies direct heat to steel (like burner to drum) then that heat is conducted to the bean mass. Agitation would be via fluidized bed vs. vaned drum rotation...
CK
If I understand correctly, in this scenario, you would be cooling the beans to fluidize/agitate them with the cool air supply from the blower, at the same time as trying to heat them with the band/metal sleeve combo. One system opposes the other and would defeat the intent of the process, or at least require much greater heat input from the band.
CharcoalRoaster
That's not what I was thinking but of course, my thinking tends to be flawed. If in a drum roaster heat is applied to the drum and air is pulled/pushed through it doesn't cool the beans down -- then in this scenario the heat applied to the pipe would also create heat in the bean mass in the same way wouldn't it since the bean mass would be in contact with the heated steel of the pipe walls?

Or are you saying that the airflow needed to loft the fluidbed will end up negating any heat produced?
Edited by CharcoalRoaster on 12/29/2019 12:02 PM
CK
A drum roaster uses mechanical force to agitate the beans. It requires much less airflow than a fluid bed to move the bean mass because the drum does the work, so heat lost/transferred to inlet air is minimal.

In a fluid bed roaster the inlet CFM is much higher, and requires more power for the temperature rise to be sufficient to roast... at least how I see it.
renatoa
As CK wrote ^^^...

Conduction heat transfer in coffee roasting is one of the biggest bogus and misunderstanding. You can't transfer heat from a plane heat source to a spherical object, via punctiforme contact area, without burning the contact point.
The most known method to roast beans using conduction is pan roasting, with deplorable results if the beans aren't permanently under a strong agitation.
Even stove placed whirley pop pot is more (auto) convection than conduction.

Back to your steel roast chamber, heated via infrared or other outer heat source.
In order to give it a chance I see this steel part of the roaster as a burner, not as a roast chamber, to avoid beans touching the hot steel, his role being just heat the air as for a regular fluid bed.
CharcoalRoaster
This is why I love this forum so much -- it's where roasters are born and also a graveyard for ideas Roflmao
allenb

Quote

CharcoalRoaster wrote:

So here's a really rough sketch of what I was imagining in my mind.

Their used for injection molding and the ones I've seen are 240v @ 2000w or higher with some specs saying up to 1200*F

https://www.dropb...d.jpg?dl=0


So, if the sketch posted is the layout you are pondering with band heater around the steel cylinder below the perf plate and would then not be transferring any heat to the beans via through RC to beans, then the only affect would be some transfer to the air stream heading up to the perf plate and a portion of the heat would be transferring to the ambient air outside the roaster due to losses from the band heater exterior surface. Due to huge losses to ambient air outside the roaster, this would be a very inefficient way to heat the air and would take lots of extra watts. You would also have a heavily stratified airstream unless there was lots of space between area of band heater and location of perf plate.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
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