Deft. Coffee Roasters. » air flow

Chaff collection box…

Dave — Thu, 17 Jan 2008 00:55:36 +0000

Okay, three last images. They simple show the difference in air flow for low and high air flow. Noticeably more chaff gets around the corner with high air flow.Here they are:

Low air flow:

High air flow:

Comparison of high and low air flow – the magenta overlay shows the difference when the high airflow was done (second):

Video of the airflow prototype (version 1.3)

Dave — Thu, 10 Jan 2008 23:34:56 +0000

I am figuring out the design of the air flow—mostly to allow for control of the air flow, but will need to catch the chaff as well. I based what I am doing on what I know of older Gothot sample roaster —why reinvent this? I don’t have one to play with, so am reverse engineering based on my memory and images I have found on the internet.This video is of the easy portion—where the air exits the roaster and enters / moves through a wind tunnel of sorts, separating the chaff from the airflow. you can see where the chaff is caught in the dead zone below the hole it enters through. Still a couple refinements to figure out, but it is working.The Cheesecloth was there cause it is a normal fan and not a n impeller, and I wasn’t sure it would work (well, it didn’t at first, which is why it is version 1.3 -)

AIRFLOW PROTOTYPE: Version 1.3 (the airbox)

Dave — Tue, 08 Jan 2008 00:23:10 +0000

I’ve been making on the fly tweaks to the form of the air box, and have almost nailed down the general design. It is based on older Gothot sample roaster designs that I have seen. I am basically re-creating this from memory and what images I could cull from the interweb. I don’t feel that I need to re-invent this part of the roaster, but am toying with how to build some efficiency into the heating, similiar to how the Kestrel roasters work. That may be phase two though.I need to run through the tests again, but feel that I am fairly close.

Learnings:

Having the air/chaff enter from an overhang (rather than flush with the back wall) creates a nice little dead zone that traps chaff quite well

That if the gap leading to the exist hallway is too large, the fan/impeller will simply pull all the chaff around the corner and out the venting—with lower airflows. The final design will have a slit of a gap.

I may add a fine mesh screen in front of the impeller entrance just to catch any errant flakes, but they could also be caught with t-shaped venting after the impeller (which I should do anyway). A tiny bit of chaff isn’t going to hurt the impeller, after all.

Next I want to repeat this with a larger amount of chaff, and with dry ice (to see what it looks like). and then begin dimensioning this out. I like that it’s really simple and works.After that, I need to add on the air as it comes from the cooling try, which sits on top of the airbox. It’s a bit more tricky, as it will feed both the airbox and the drum—toggling between the two…