[Stoves] Trials on TLUD Gas Burners - Burner Diameter

[Julien Winter]

Dear Crispin and Stovers;

Thanks for your comments.  They are very insightful, as always.

You make a good point that I should mention viscosity.  I have read that
viscosity of gases increase as their temperature increases, but I don't
know why.  Does anybody have an answer and a reference?

The reproduction of slide 18 may not be very clear.  I am reporting all my
gasification rates as mg/min/cm^2.  Unless my equation is in error (side
14), this is loss of fuel dry matter / unit time / per unit area of TLUD.
I divided by the area of the TLUD to give a 'specific' gasification rate
that could be directly compared measurements on other TLUDs of different
diameters.

 When designing an experiment, the researcher often wants to hold certain
features constant, whilst varying an experimental factor.  This often leads
to situations which are not quite optimal.  In my case, I held the diameter
of the secondary air holes constant, whilst varying burner diameter.  That
way I was isolating the effect of diameter.  However, under practical
circumstances, it may be better to decrease the size of the secondary air
holes as diameter decreases.  Thus the 1x burner may work better with
smaller holes.  (I did try this on 16% moisture fuel with no success.)  So
a more thorough experiment would be to vary both hole size and burner
diameter.

I have varied hole size in another trial.  The gasification rate increased
when I increased hole diameter, but I decreased the number of holes to keep
the total area for secondary air constant.  I had 16x 1.45 cm, 12x 1.75 cm,
and 8x 2.05 cm holes.  However, this is another example of keeping
something constant and producing an impractical consequence.  If you
increase the hole size, but decrease their number, the space between holes
becomes too large; so in practical terms, you can't increase hole diameter
and keep the total area for secondary air constant.  The burner with 8 x
2.05 cm holes had to be scrapped.

The good thing about small prototype TLUDs is that you can run many trials
at low cost, and develop theories and hypothesis to be corroborated later
on full size models.  This trial had 90 experimental units for the lowest
three moisture levels.  I would not like to have tried that with a full
size stove without having run prototypes first.   However, when it comes to
developing real world stoves, prototypes will not suffice.  In the end, we
have to get the response curves for changing the dimensions of working-size
burners.

The MOST IMPORTANT thing I have discovered is that if you mix canned chick
peas with canned tomatoes, a lot of fried onions, and curry paste ... and
eat this mix with rice several times a day for a few weeks, you will have a
lot of tin cans.  It helps to wash it down with coffee that comes in large
cans.

Cheers,
Julien


-- 
Julien Winter
Cobourg, ON, CANADA
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