Re: Second rapid boiling test - Jim Ross

["Crispin" <crispin@newdawn.sz>]

Dear Tom

>I recommend the format you have used to others aspiring to
>quantitative tests or winning coiling contests.

My nephew Ryan at the Univ of Alberta Edmonton also suggested a humidity
reading, and/or air pressure and altitude.

>1) I envy you your 2 gm precision on your (digital?) balance.

Yes, it is a 12.5 Kg with 2gm divisions, just big enough to handle a small
stove though not big enough to handle the Baking stove.

>2) I presume the data was taken "by hand"

We recorded the mass of everything individually before and after where
necessary.  The stove puts out FAR too much heat to run this test on top of
the scale.  The stove body near the pot is something like 400 deg C.

>3)  thermometer or thermocouple?

Thermocouple.  0-999 Deg C

>4)  What did you use as a heating value for the wood/paper?

15 MJ.Kg

>Looks like 4.44 MJ/.326 kg = 13.6 MJ/kg, seems low even for wet wood.

Don't forget to subtract for the wood left at the end.  It should work out
as 4.44 MJ/(15Mj/kg)

>5)  It would be particularly useful if you could give the moisture content
of the wood.

I will try to get something on this.

>It only requires a thermostated oven (electric or gas) that you can
maintain at 105C +/- 5 C.

I will put it in the microwave on high for a while until it hisses.  I
actually bought the oven first to dry soil samples!  With my wife in Canada
for 2 months I am heating my meals with it too.

>I'm guessing you might be 15-20% moisture (wet basis)
>in your high humidity environment.

I agree and the figure 15 MJ/KG is reasonable as a result.  In this test it
is not all that relevant as the efficiency is pathetic.  The temperature of
the 'chimney' was outrageous.  It burned the tin plating off the stove top.
I will try to get a fire temp on the next test - measured where it passes
under the pot.  It is going to be over 900 I am sure.  I can't put the
thermocouple in the fire as the wire will burn away before I can get it out
again.  The asbestos woven insulation over the pair of wire vaporizes in the
heat.

>However, an equally important criterion is "turndown"
>if you are interested in fuel efficiency.

I can get the power down under 1KW but it can be lower by not refuelling
very often.  It is a very easy thing to do.  Lower the power output with a
vert hot stove has been a problem.  The Tsotso was pretty good on that
score.  I would say 7:1 variation.  Choking it too much leads to unburned
smoke.

>Your ability to boil in 3 minutes is excellent for the contest,

We are amazed.  It is well under 3 minutes for a well built fire.  Jim's
test didn't com off so well because of all the humidity and the fuel shape
and quantity.  I am going to give each of the guys in the workshop a chance
to build a "fast fire" are run one test each to get an average.  With dry
material and no overloading (I think 325 gm was too much) I am sure we will
reach 120 seconds, match to boil.  It looks like 15 blow torches under the
pot when it is running!

>How is the Basintuthu for simmering?

Excellent and the way to get it is to let the fuel run down, the steel cool
off a bit then lotsa choke.  The briquettes (which will not give us a 3
minute boil!) are very good for simmering at 1/4 throttle = 7-8 minutes/MJ.

Regards
Crispin


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