topbanner.gif
Login
Username

Password




Not a member yet?
Click here to register.

Forgotten your password?
Request a new one here.
Shoutbox
You must login to post a message.

snwcmpr
03/20/2019 4:17 AM
Eth Yirg Nat Idido Gr1 today.

snwcmpr
03/18/2019 8:15 AM
1 lb roasted lasts a week. I can taste the flavor increase to peak, then drop after. Still very good, but interesting to follow the wave of flavor rise and fall.

snwcmpr
03/11/2019 4:10 PM
Roasted Panama Gesha Esmeralda yesterday. Yummy.

Beebee74
03/11/2019 3:10 PM
I seem to have lost any roasting touch I thought I had. Very frustrated to be wasting time and money. I’m hoping someone can provide some insight on roasting at high altitude. I’m at 4400ft. Thank

aicardo
03/07/2019 8:50 AM
tb

Users Online
Guests Online: 1

Members Online: 0

Total Members: 5,859
Newest Member: Hozer56
In Memory Of Ginny
Donations

Latest Donations
renatoa - 2.00
JitterzZ - 50.00
PRABHATH COFFEE WORKS - 10.00
John Despres (Scene... - 25.00
snwcmpr - 10.00

View Thread

Who is here? 1 guest(s)
 Print Thread
Is ET drop during the roast ok?
TXRoaster
I have been roasting using the Hottop b-2k+ with Artisan 1.2. I have been working on eliminating the “crash and flick” described by Scott Rao. I have been successful in eliminating most of the flick, crash but to do so I have been dropping my power during 1C. The BT continues to rise and the delta BT continues to fall but never goes below +5. However, my ET temp levels off and then starts a slight drop during or at the end of 1C. My question: If everything else in the roast looks ok, is it acceptable to have a leveling off and slight decline in ET during and after 1C to the end?
 
TXRoaster
After cupping my lastest roast, I would have to say no. The roast was flat, underdeveloped, grassy. It looks like you have to have a rising BT, declining delta BT with no flicks or crashes AND a rising ET to be successful. I am trying to use my sight and smell as well but I am not experienced enough on that yet. The roast had a weak 1C and by my limited experience, my gut was telling me the roast was going to be underdeveloped. I’ll go back and try again.

I am new to this but being able to roast, sight, sound and with Artisan 1.2 is a blast! Being able to set up a roast using an alarm file in Artisan is really fun.

Any advice on roasting with the Hottop would be appreciated
 
allenb
However, my ET temp levels off and then starts a slight drop during or at the end of 1C. My question: If everything else in the roast looks ok, is it acceptable to have a leveling off and slight decline in ET during and after 1C to the end?


I'm roasting in a 1lb gas fired drum and what you're describing is exactly what takes place during all of my roasts. In a drum roaster, your primary heat source is the drum to bean long wavelength IR, not the air surrounding or passing by the beans. During the power reduction approaching and during 1C, ET will drop when the heat source that heats the air stream is reduced, even though BT is still climbing. Some drum designs may not perform this way but many do.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
Now you confused me... :) all knowledge I accumulated so far about (real) drum roasting tells that:
- during dry we have conductive heat majoritary
- during Maillard we have a mix of conductive and convection
- during development there is finally some radiant component that matters

Regarding OP issue, I think this is the normal behaviour of a roast profile whatever machine you have.
Mine is preponderent radiant+some convection and roasts have the same allure: ET tops when into FC, then remain stationary or decrease, and BT continue to rise, but mildly than before.
DIY: TO based IR to bean 750g
Moded commercial: Dieckmann RoestMeister, Nesco, popcorn.
TC4ESP, PID controllers, MS6514 USB/Artisan/Apps
Grinder: MBK Feldgrind, mod'ed Porlex to 47 conical burrs, vintage PeDe Dienes
 
allenb
Most discussions about drum roaster heat transfer whether between non-professional and non-academic or between people with engineering backgrounds, have for the most part assumed that conduction between drum wall and beans is the primary mode of transfer in a solid drum roaster. This has never been true and a couple of studies on thermodynamics related to drying systems equipment showed the difference in heat transfer efficiency between heating surfaces and differently shaped particles. Particles with mostly flat surfaces (75% or so) were able to efficiently accept heat from a hot surface while particles with mostly round or curved surfaces had very poor conductive transfer efficiency. Coffee beans, even on the flat side are mostly curved or spherical and have terrible conductive heat transfer efficiency. To make matters worse, the percentage of the time one bean out of the batch actually makes contact with the drum surface is a very short time out of the total roast time.

If heat transfer were only possible via conductance between drum and bean, the roast would take forever and the bean structure would be damaged badly.

Heat transfer in a single wall drum roaster is mostly long wavelength infra red emanating from the drum wall. This is possible with a relatively low surface temperature due to the large surface area involved. Surface temperatures only have to be in the low 500's F to efficiently roast coffee due to the close proximity of the beans to the radiating surface.

Convective heat transfer, although less than IR, is at play during most of the roast except during the so-called development phase when burner output is reduced to allow lowering rate of rise.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
fatboytx
I am trying to reduce my drying time and lengthen my 1st crack. From the above notes, it seems like I should be increasing the charge temp ... delaying when I drop beans into the drum. My B2K auto mode says to drop at 167F but I've been dropping beans at about 210F. The resulting drying time is about 6:30 mins. What say the crowd?

My roasts are a solid ok. Haven't had a great roast yet. So, I am shooting for a 4-4-4 roast profile.

Thanks, FB
 
allenb
Hi FB, yes, increasing charge temp would be the ticket if trying to shorten dry time. Try various dry times with keeping the rest fairly equal and see what differences show up in the cup. Lots of variables to sift through but you will eventually find what profile shines with various coffees.

Let us know results in the cup with the change in dry time.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
allenb
alllenb stated:

Heat transfer in a single wall drum roaster is mostly long wavelength infra red emanating from the drum wall. This is possible with a relatively low surface temperature due to the large surface area involved. Surface temperatures only have to be in the low 500's F to efficiently roast coffee due to the close proximity of the beans to the radiating surface.


After much experimenting and reading, I still maintain that in a single wall drum gas or electric under the drum heated roaster that the primary heat transfer mode is long wavelength IR from drum surface to bean but I'm finding that the statement above ( surface temps only have to be in the low 500's) is not accurate. I'm guessing the drum wall surface temperature is closer to the high 700's F near the lower portion of the drum where flame or electric element is producing the most transfer.

If anyone has an accurate means of measuring your single wall drum inner surface temperature throughout the roast I would love to hear the results. The problem is the beans are contacting the area needed to be measured. Measuring the outside of the drum just past the point where flame is visible might be of value also.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
The flame does not touch directly the drum, as far I am aware about some common builds.
What about the electric roasters, their drum surely is not in the 700F ballpark...

Also, how should we take the 270C max temp limit, that alter the cell cellulose matrix, if drum would be so hot ?

I am not roasting in a drum, but in my tests I measured my "roast chamber" wall temp, an Ikea steamer insert, and it is the coolest place after the bean in that setup. That is no wonder because in my case the roasting is a mix of hot air and direct to bean IR.
 
allenb
renatoa wrote:

The flame does not touch directly the drum, as far I am aware about some common builds.
What about the electric roasters, their drum surely is not in the 700F ballpark...

Also, how should we take the 270C max temp limit, that alter the cell cellulose matrix, if drum would be so hot ?



The combustion gas temperature hitting the drum will be close to the same regardless of flame contact or gap in between assuming it's not a large gap.

The 270C limit suggestion by Carl Staub and others was not drum wall temperature but was environment air temperature within the drum.

I've not been able to find anyone who has successfully and accurately measured drum wall temperature very near the point in the drum where the major mass of beans occupy.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
renatoa
The combustion gas temperature hitting the drum will be close to the same regardless of flame contact or gap in between assuming it's not a large gap.


I meant the perforated shields that are placed between flame and drum, not an air gap.

The 270C limit suggestion by Carl Staub and others was not drum wall temperature but was environment air temperature within the drum.


Can we consider the contact point between bean and the +500F wall as part of the environment ?

I've not been able to find anyone who has successfully and accurately measured drum wall temperature very near the point in the drum where the major mass of beans occupy.


During preheating seems more doable, when the whole system reach equilibrium, opening the drop door and using an IR/laser spot thermometer...
 
allenb
renatoa wrote:

The combustion gas temperature hitting the drum will be close to the same regardless of flame contact or gap in between assuming it's not a large gap.


I meant the perforated shields that are placed between flame and drum, not an air gap.

The 270C limit suggestion by Carl Staub and others was not drum wall temperature but was environment air temperature within the drum.


Can we consider the contact point between bean and the +500F wall as part of the environment ?

I've not been able to find anyone who has successfully and accurately measured drum wall temperature very near the point in the drum where the major mass of beans occupy.


During preheating seems more doable, when the whole system reach equilibrium, opening the drop door and using an IR/laser spot thermometer...


The actual temperature of the environment, even at point of contact with the drum wall, to my knowledge, has not been measured and published in the journals and papers commonly available to us. The infinitesimally short contact time that one bean truly makes contact with the drum wall will not allow equating the drum wall temperature with environment temperature.

During preheating seems more doable, when the whole system reach equilibrium, opening the drop door and using an IR/laser spot thermometer


The temperature we want to measure (drum wall) can only be measured while all elements of the thermodynamic process are at play. The heat exchange from drum to beans and air has to be at play or the temperature measurement is of no value.

I'm going to start another thread in a different forum so this can be discussed outside of the Hottop Roaster forum.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Jump to Forum:

Similar Threads

Thread Forum Replies Last Post
Roast profile from hacked P1 Roasting Profiles 3 03/18/2019 10:53 AM
Uniformity in Roast Roasting Coffee 6 02/13/2019 5:02 AM
SR 500 temp drop Fresh Roast 8 and NEW SR 500 6 02/01/2019 2:05 AM
Roast Control Options ??? Fluidbed Roaster 3 01/19/2019 8:26 AM
Holiday Roast Exchange Site Announcements 10 12/20/2018 2:24 AM
Homeroasters Association Logo, and all Content, Images, and Icons © 2005-2016 Homeroasters Association - Logos are the property of their respective owners.
Powered by PHP-Fusion Copyright © 2019 PHP-Fusion Inc
Released as free software without warranties under GNU Affero GPL v3
Designed with by NetriX