[Stoves] [Fwd: Superficial Velocities of Power gasifiers and WoodGas Stoves]

[frank]

Stovers,

Trying to understand the movement of air through small fuel I set up a 
simple experiment (see below) where I measured the time air took to pass 
through an empty one liter chamber and again with the chamber filled 
with plastic balls (fuel). Thinking the time of travel would be faster 
with the balls due to reduction of void space by ~50%.causing the air to 
rush faster past the balls.
Flow was constant at 0.5 LPM.

I found just the opposite! It took about 18 seconds without the 'fuel' 
and about 56 seconds with the 'fuel' between the injection of CO2 and 
the peak height. ????

Crispin mentioned awhile back he thought Surface Area was an important 
factor to know.
A) I am wondering if this increased surface with the balls is the cause 
of the increased time it took for the air to pass?
B) Can we determine the surface area of a small fuel doing this 
experiment (standardized against beads).
C) Can we calculate the speed air is going past the fuel surface with 
this experiment?
D) Am I (once again!) way off base?


Thanks for any enlightenment.

Frank



> EXPERIMENT
> Purpose:
> To show that when fuel fills a container the air travels faster 
> through the fuel than in the same container without fuel due to the  
> reduced void space.
>
> Set-up:
> I used a one liter squeeze water bottle for the fuel container and 140 
> plastic spheres that each are 3.7657 cm3 for the fuel.
>
> Train from back end to front:
> flow meter and needle valve set for 0.5 LPM
> Aquarium air pump sucking air from up stream and flow controlled by 
> needle valve. Steady flow.
> CO2 analyzer
> Out flow of the water (fuel) container piped to analyzer. Fuel 
> container (A) not filled and (B) filled with total 527 cm3 plastic 
> balls (fuel) leaving 47.3 % of total void space.
> Two hole stopper fitted where the cap was. One hole for injecting in 
> CO2 and the other with continued flow of CO2 free air being drawn 
> through the train
> CO2 free air comes from head space at the top of a large bottle of 
> water with NaOH to remove the CO2 from supply line
> Compressor on roof supplying air to the NaOH scrubber.
>
> Procedure:
> (A)
> System run until CO2 meter indicated a steady baseline with CO2 free 
> air and *no fuel in the fuel container*.
> 250uL CO2 injected
> Time from injection to high point of peak.
>
> (B)
> System run until CO2 meter indicated a steady baseline with CO2 free 
> air and fuel container *filled with fuel* .
> 250uL CO2 injected
> Time from injection to high point of peak
>
> Results:
> (A)
> Time (seconds) from injection to high point of peak (NO Fuel)
> 18
> 17
> 18
> 16
> 20
>
> (B)
> Time (seconds) from injection to high point of peak (Fuel)
> 63
> 56
> 58
> 56
> 50
>
> Conclusion:
> It takes longer for air to pass through the restricted flow (due to 
> fuel) than with an open fuel container.
>
>
> Frank
>
>
>
>
>
-- 
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