[Stoves] air for gazification

[frank]

Greetings stovers,

Yes - I did a search on ASK for my new word 'Superficial Velocity' and 
it lead me back here and to Tom Reed. Who would have guessed : )

But that leads to another question (no end in sight!!). My thinking is 
we cannot measure the  SV in the fuel bed based on flow meters  of the 
gas entering the stove.  If we have a SV of 10 m/s and we stick in fuel 
that takes up half the space the SV will increase in the fuel bed to 20 
m/s  because there is half the void space available and the gases must 
travel faster. I think its this measurement of velocity through the fuel 
that is important and the speed of the gas as it goes through the 
primary burn. Not sure, but from reading the procedure I think this was 
not determined. I think determining the speed of gas around each little 
fuel particle is a goal. I think if we have gas going through a 50cc 
space, and the space is one large opening, the gas will travel slower 
than if the 50cc void space is around many small particles where the gas 
is squeezed and redirected on all different directions. Perhaps its the 
speed of gas around each fuel particle that is important. All this is 
probably not important with large fuel, but I think could be very 
important with small fuel and the TLUD where the gas is blowing the heat 
away from the fuel.

Perhaps this can be calculated based on the void space -but I think not 
because I think shape and size of the void space will effect the SV. 
Another way may be to pull gas from a port at the bottom and another at 
the top at the same time and measure the distance between the two peaks 
on a chart recorder from spiking with CO2 in the inflow gas. Problem I 
see is the CO2 meter and recorder may not be fast enough for a 'stove' 
size fuel chamber and the fuel chamber may need be extended a much 
greater distance packed with the fuel of choice.

I am not sure how the pressure drop system works.

Thanks
Frank

.




Bruno M. wrote:

>~~~~~~~~~~~~~~
>At 03:37 20/06/2007, Jeff wrote:
>  
>
>>Frank wrote:
>>    
>>
>>>Is there an 'air
>>>conductivity'
>>>term for air going through a packed material?
>>>      
>>>
>>Maybe not what your looking for but there is "Superficial Velocity" (SV).
>>Jeff
>>
>>--
>>Jeff Davis
>>Some where 20 miles south of Lake Erie, USA
>>_______________________________________________
>>    
>>
>
>A good idea Jeff,
>
>... for flowrates in a (packed)bed:
>
>Vs =  Superficial velocity;  Vs = Q/A  where Q is the volumetric flow 
>rate of the fluidum
>                                     and A is the cross-sectional 
>area of the bed
>Vs is in m/s if Q is in m3/s and A is in m2
>
>And for a good explanation about " Superficial Velocity " in gasifiing Stoves,
>some dude called Tom B. Reed  ;-)  and his fellow's wrote in 1999 a 
>nice 8 page PDF titled :
>" SUPERFICIAL VELOCITY - THE KEY TO DOWNDRAFT GASIFICATION "
>maybe you can find it on the Stoves pages or else here :
>www.woodgas.com/Superficial%20Velocity.pdf
>
>no need to reinvent the wheel.
>;-)
>Bruno M.
>
>
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>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com