Airflow meter

[Angela]

A quick look on Google Scholar shows someone has bean modelled before! https://www.sciencedirect.com/science/a ... 7412002063 but behind a paywall. Chris, you can walk in to Dunedin Uni library and ask for free online access!

[Angela]

Well lets wrap this up then.
The lack of further engagement in this thread probably signals the 'da management' do not want to wash their dirty linen in public.

Air roasters are now ubiquitous. As far as I can see they all ignore the big issues of stable air flow and proper computation of the thermal energy transferred to the beans. They will likely roast OK - some of them - some of the time.

I've been pushing the the fact that air pressure changes alter a roasts quality for over a year. I was heartened to see of the acknowledgement of the issue in this thread at last.

I've recently imagined the effect of air humidity. If you roast in a stable weather environment where the days are wall-to-wall sunny and dry you would not know what I'm talking about. But if you roast in a changeable climate you'll know that wet day roasts stand a good chance of being rubbish; or at least different from a roast a few days before. There is a repeatability problem folks!

But the silence here signals no one at Kaffelogic wants to talk about it. I'm often a bumptious idiot and make loads of mistakes; I can recognize that. My style most likely comes from my experience as a Senior Lecturer teaching post-graduates; it can be flippant, direct, challenging and know-it-all. My knowledge is broad skim lacking depth but I do think I have something relevant to say. I did a very quick trawl of the research around coffee roasting parameters. I found a couple of pertinent quotes, which didn't take long. If you don't want to believe me then believe these two Doctors of Science.

Author: Schenker, Stefan. 2000 taken from https://doi.org/10.3929/ethz-a-003889071
Hot air Humidity:
"The humidity of the hot air must be considered as another important process parameter. … Elevated humidities cause an increased specific heat capacity of the hot air and result in more efficient heat transfer. In addition, it is assumed that some reaction and changes that depend on water content are also affected."

Author: Budryn, Grażyna et al. 2013 https://www.tandfonline.com/doi/full/10 ... 013.805769
Correlation Between the Stability of Chlorogenic Acids, Antioxidant Activity and Acrylamide Content in Coffee Beans Roasted in Different Conditions
"Studies have shown that such parameters of coffee beans roasting process as roasting air velocity and humidity, next to temperature and time have a significant effect on the concentration of acrylamide in roasted beans."

But pertinently both of these researchers whilst acknowledging the role of air moisture in coffee roasting failed to get to grips with it. The prize awaits the person(s) who can.

We live in World where we can now model and predict behaviours of things before the expense of manufacture. Recently in the history of mankind, we humans in general, have learned how to move from the empirical - suck it and see - method of design and manufacture to the modelling of outcomes in software prior to a physical product being produced. For such computer modelling I give you the example of a simple kitchen door hinge. 50 or 60 years ago the hinge knuckle would protrude in front of the lay-on-door and visually impair the look of a run of cabinets and make cleaning a little more awkward. With the advent of the computers and CAD systems it became possible to 'model' in virtual reality. Designers were able to imagine, design and immediately produce a model for a hinge, involving multiple linkages, inside a computer. The hinge, when manufactured and fitted wholly to the inside of the cabinet, would allow the door to open clear of the carcase and swing through more than 90 degrees. The computer saved hundreds of man hours making umpteen real life examples of a hinge to test. Empiricism in the developed World began to die that day.

Technology has moved on in the intervening years. Aircraft and F1 cars' performance used to be modelled in a wind-tunnel, and still might be for final confirmation of parameters, but more and more a new method of predicting outcomes using software called Computational Fluid Dynamics is being used to mathematically model the performance of aerofoils and body shapes in moving air.

The literature I'm reading suggests hot air roasting is as much about heat transfer to the bean from contact with surfaces as from the air. The chamber too has an effect. I've wondering why there isn't a spike smoothly rising in the centre of our chambers around which the beans might rotate? I'm thinking beans bouncing is the wasted energy of chaos. I'm wondering if the a torus shape as used in the Tokamaks of nuclear fusion experiments might prove a better chamber design? I'm wondering if CFD software might usefully model the whole process? But these are 21st Century approaches and it would be remarkable if a small start-up, working from an enterprise centre, on a remote island could ever develop the vision and wherewithal to catch up. I chose to decline the chance to invest further in the company. I still see no reason to change that decision

[Geronimo]

Angela

Interesting reading, as are your comments always, very educational. Something I noted, is that you commented on your machine appears to cause tipping more now???

As an aside on the CFD, the America’s Cup 75ft yachts racing at the moment down here in Auckland are all modelled on the computer, in the rules this time around no tank or wind tunnel testing was allowed. Your boat Britannia (Rita for short) is doing extremely well. If you have seen them and know what I’m talking about, they are impressive beasts foiling around at multiple times the wind speed (53 knots is the fastest so far in the competition).

Cheers

[kaffelogic]

Hi Angela

We are certainly following this up, hence the plans to incorporate air pressure, temperature, and humidity sensors in an extension module when we build the Bluetooth connectivity module. However, we do not have have a large R&D budget, and although I would love to be able to complete the modelling project that you have outlined it is currently beyond our resources to do so. In the meantime, if other community members would contribute their experiences of roasting in differing weather conditions, especially humidity, this will be much appreciated as we try to build a better understanding of the practical implications for roast replicability. This will help us set priorities when we have resources that we can allocate to modelling.

There are some interesting questions here, the key question being can we, by adjusting fan speed and heater power alone, achieve very high roast replicability in the face of significant variation in humidity and air pressure? Another question is whether bean moisture content needs to be controlled or whether fan speed and heater power adjustments can compensate for differences in bean moisture content?

I will be following up the article that you provided in the hope that this might provide a model that can be implemented relatively easily.

The Kaffelogic is a very flexible piece of kit, and it makes experimental work very doable, especially when results are based on cupping and not modelling or chemical analysis. I invite other community members to let us know your experiences of how weather affects your roasting in the cup.

Chris

[lancruiser]

The Kaffelogic is a very flexible piece of kit, and it makes experimental work very doable, especially when results are based on cupping and not modelling or chemical analysis. I invite other community members to let us know your experiences of how weather affects your roasting in the cup.

Hi Chris, looking at my logs when I roasted the same bean in winter and summer, I really can't see any differences. I cannot identify any pattern that is related to weather or seasons. Perhaps the difference just eludes me.

Having said that, I do back to back roasts - usually 5 roasts of the same coffee to last me a week. I have noticed that the first roast from a cold roaster is usually the odd one out. For most coffee, the first crack is at a lower probe temperature to the subsequent roasts. Obviously, the logs at the start of the first roast looks different as well.

Perhaps, as a low hanging fruit, you can introduce a manual warm up cycle in the menu to heat up the roaster without any beans? This will ensure that every roasts start from a known consistent state.

[kaffelogic]

Hi Chris, looking at my logs when I roasted the same bean in winter and summer, I really can't see any differences. I cannot identify any pattern that is related to weather or seasons. Perhaps the difference just eludes me.

Thanks for sharing your findings. It may of course be that humidity in your house doesn't change much. Large swings in humidity might make a noticeable difference. More research needed.

Perhaps, as a low hanging fruit, you can introduce a manual warm up cycle in the menu to heat up the roaster without any beans? This will ensure that every roasts start from a known consistent state.

I take it you are using the latest firmware? The cooldown takes the roaster to thermal equilibrium, the catch being that with the motor running the transformer pumps out enough power to lift that equilibrium point 8 deg C above ambient. The warm up cycle would have to warm the whole unit by that 8 deg C. This is another topic, but I am more inclined to automatically modify the initial part of follow-on roasts to bring them into line - something that I will explore further.

[lancruiser]

I take it you are using the latest firmware? The cooldown takes the roaster to thermal equilibrium, the catch being that with the motor running the transformer pumps out enough power to lift that equilibrium point 8 deg C above ambient. The warm up cycle would have to warm the whole unit by that 8 deg C. This is another topic, but I am more inclined to automatically modify the initial part of follow-on roasts to bring them into line - something that I will explore further.

Yes, I am using the latest firmware. Cooldown is a bit long but acceptable. I will be happy with any solution as long as every roast is consistent.

[kaffelogic]

Yes, I am using the latest firmware. Cooldown is a bit long but acceptable. I will be happy with any solution as long as every roast is consistent.

If you are able to send me some logs, especially sets of same beans, same day, where FC has been logged showing the difference that you are experiencing, that will give me data to work on faster than I can generate it myself. I'm hoping I can provide a solution quite quickly.

[lancruiser]

If you are able to send me some logs, especially sets of same beans, same day, where FC has been logged showing the difference that you are experiencing, that will give me data to work on faster than I can generate it myself. I'm hoping I can provide a solution quite quickly.

I have sent you 5 back-to-back roast logs in an email. I Hope they are useful.

[kaffelogic]

I have sent you 5 back-to-back roast logs in an email. I Hope they are useful.

Thanks for the logs. It turns out the issue is caused by turning the roaster off while you are emptying it, which does affect the ambient temperature measurement. Changing your emptying technique should enable you to leave it turned on. See https://kaffelogic.com/community/viewto ... =291#p1861

That, of course, still leaves the air pressure/temperature/humidity question open. I appreciate your noting that you haven't noticed any weather-related differences in your roasts, but maybe you just don't have English weather to contend with! I would appreciate further comments from anyone who roasts in wildly varying ambient conditions.