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

[frank]

Dear Penn,

Robert Penn Taylor wrote:

> Frank,
>
> I have a few questions for you about your setup:
>
> 1. What are the details of the flow measurement, especially what type 
> of flowmeter?

It is a needle valve below a meter with a small ball that floats  in the 
air flow (sorry-forgot the name of the type meter)

> 2. Are you monitoring pressures in the system? If so, where and what 
> are they?

No - only keeping the flow constant. The fish aquarium pump pushes more 
than enough air and I reduce it with the needle valve to what I want.

> 3. When the CO2 is injected, is it via a pressurized pulse or are you 
> relying on a venturi effect to pull a measured volume of CO2 into the 
> system passively? If it's a pulse, what is the timing on it? Either 
> way, what is its pressure?

I inject using a syringe from a pure CO2 gas flow from a CO2 tank 
bleeding out air.  The intergrater on the computer is going. I wait and 
inject at a specific time ( being measured every second) Record that 
start time and then record the time when the peak height is at the 
highest.  No pressure.

> 4. I assume your analyzer measures CO2 concentration. If you integrate 
> the concentration the analyzer reads over the time of the experiment, 
> do you end up with the same amount of CO2 you put into the system?

I think the amount of CO2 is not important. As long as I use the same 
amount for both (A) and (B). I am looking for Time of Travel.

>
> I suspect you've set up a constant volume flow rather than a constant 
> mass flow. Your hypothesis of faster movement in the restricted setup 
> is based on the assumption of constant mass.

Over my head! 

Thanks
Frank


>
> -Penn Taylor
>
> -- 
>
> Robert Penn Taylor
> Graduate Research Assistant
> Department of Mechanical Engineering
> Iowa State University
> (515) 294-5311
>
> frank wrote:
>
>> 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