[Stoves] Equipment required for testing stoves

[Alex English]

Ron,

On 09/12/2012 8:33 PM, rongretlarson at comcast.net wrote:
> Alex etal
>
>   Thanks for the cite.  I think I understand most of the plot - which 
> was of amazing duration!.   I am especially amazed at how uniform (and 
> high) the flame temperature was in the late time plot, even as the 
> other plots were dropping.
>
It is a very steady gas producer. Conditions are constant except for the 
distance and path composition between the pyrolysis front and the 
burner. If it can be done over 100cm then why not 200 or 300.
> a.   Since you have this one from 2000, you probably have quite a few 
> more - from which I/we might extract a good bit more information/  Any 
> other similar plots around that you can post?
No I don't.
>
>      b.   I am surprised that the "pyrolysis gas temperature" was so 
> much lower than the temperature of the char. Where was the probe for 
> this measurement - and had there been some mixing of secondary air at 
> this point?
No mixing of secondary air at that point. That occurs in and above in a 
5cm burner mixing pipe.  The tmperature difference is largely due to the 
nature of unshielded thermocouples in gas.For the most part 
thermocouples radiate away heat according to the temperatures of the 
surfaces that make up the sphere around them. A thermocouple buried in 
the pellets that are all carbonizing at 700C will give a fairly accurate 
measurement. A thermocouple in the gas above the top of the pellet bed 
will radiate to the pellet bed and, in this case the uninsulated 
container walls. The more that pellet bed shrinks the larger the portion 
of the radiant sphere that is the cool container walls. The larger the 
thermocouple, the greater the radiant cooling , the lower the 
measurement. The higher the temperature the greater the radiant loss, to 
the forth power. All the gas is also radiating and convecting heat to 
the container walls. So there are two reasons for a slow drop in gas 
temperature, and one reason for not trusting either. The same holds true 
for the absolute value of  post combustion measurement.

There are gas-/aspirated pyrometers which shield a thermocouple with 
ceramic layers that approach gas temperatures and give better numbers. 
We will soon be using an 10 footer to probe the chain grate stoker 
gasses in carbonizer- pyrolysis-gasifier mode.

Grate fun.
/
>
>      c.  What is the present disposition of this equipment?
Its in the recoverable bone yard. I should have shown it to Crispin when 
he was here.....or perhaps not:)

Alex
>
> Nice work
>
> Ron
>
>

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