[Stoves] Comments about T-LUDs

[Thomas Reed]

Dear Gasifiers and Stovers:

The Downdraft and Inverted downdraft (or TLUD, thanks, Paul Anderson) 
are in many ways similar, but in one way quite different. 

The superficial velocity (gas production rate/area of pyrolysis zone) of 
the the Downdraft gasifier must be greater than ~0.05 m/s or natural 
convection begins to take over and smoke comes out the top.

The SV for the IDD (TLUD) is typically less than 0.1 or you will blow 
the charcoal bed out the top and sparks and soot all over.  The heat 
rate of downdraft gasifiers is typically 1 M Btu/ft2-hr, while for our 
IDD/TLUD camp stove it is ~100,000 Btu/hr-ft2.  (Recommend buying one at 
Woodgas.com and testing both in stove mode and gasifier mode (close off 
combustion air holes). 

TOM REED      BEF



Crispin Pemberton-Pigott wrote:
> Dear Andrew
>
> This sounds right to me - I have been wondering all along why the TLUD is 
> considered to be an IDD.  It is not really the same after all.  Micro 
> currents of air/gas will definitely affect the way heat moves around the 
> pellets (or elements) of the pyrolysis front.  It can't work exactly the 
> same when inverted.  Your analysis looks spot on to me!
>
> Thanks
> Crispin
>
>   
>> ...I think there is a slight
>> difference in the way the tlud works compared
>> with the down draught
>> and that is to do with how the heat is transferred  because the
>> convection currents work differently... AJH 
>>     
>
>
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