HomeRoast Digest


Topic: Convection and Conduction ---> was: HG: air roast or drum (53 lines)
1) From: Tom & Maria - Sweet Maria's Coffee
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I have my analog thermometer right beside the inlet I blow air thru. 
I'm suspecting that the blast of air move the hot air in the grill 
around and raises the temp on the thermometer but probably the grill 
itself does not raise that much but with added 02 is does give the 
flames some added air and they do raise a bit, and with 
convection hot air it  raises the temps on my thermometer slightly, 
 but with just a short blast it should only be temporary at best.
But with a slow amount of air flow it should help in the roasting 
process much like the Dietrich.
I talked with a roaster here in town who roasts with a 12Kilo 
Dietrich and he said that with the air control lever in one  position 
there is 25% air flow thru the drum and when he dumps the batch into 
the cooling tray or flips the lever another position it puts 75% air 
to the cooling tray and 25% thru the drum. And in another position he 
can blast the drum with 75% air to blow the chaff out of the drum.
I guess the blast I run thru my drum and grill is such a small 
blast adds 02 to the fire and gets it slightly hotter then it just 
stirs up the heated air and that is why the temps rise a bit.I have 
noticed after the blast even with the burners on low to med that 
the flames get higher and sounds like it does when the grill is on 
high for 10 sec or so.
  It does blow the chaff out of the drum and even out of the grill 
thru the exhaust at the back.
Still experimenting
RK
I think you are dead on Ron, and my years of Diedrich experience 
jives with that too: up to a point, more air flow can raise drum 
temperatures by providing more oxygen to burners. The issue with 
Diedrich for may is that the burners are ceramic plate and are a bit 
underpowered, so the possibility of too much air flow through the 
drum can stall roasts. My Probat has more metal, more conduction, and 
will roll right through prolonged air flow increases. (well, up to a 
point). Both have their strong points. But in short, air flow is a 
great way to manipulate roasts, and adding some control to a grill is 
a great idea, my .02 cents.
Tom "leaving soon, wish me luck" Owen
--
                   "Great coffee comes from tiny roasters"
            Sweet Maria's Home Coffee Roasting  -  Tom & Maria
                      http://www.sweetmarias.com                Thompson Owen george_at_sweetmarias.com
     Sweet Maria's Coffee - 1115 21st Street, Oakland, CA 94607 - USA
             phone/fax: 888 876 5917 - tom_at_sweetmarias.com


HomeRoast Digest