[Stoves] Vietnamese brick kilns

[Crispin Pemberton-Pigott]

Dear Marc

 

Your post was a 'keeper'. Thanks so much. You are doing very good work with
nearly nothing backing you. 

"What I think is responsible is that the particular chemical structure of
rice hull (high ash, a silica skeleton) acts as a brake on the "char
reactions" ."

I suspect it is worth looking at the ash and char content to see if there is
not a mistake being made relative to the application of the Siegert
constants. That will affect the final number and are rooted in the chemical
composition of the fuel, which has of course changed.

 

I believe we will one day be able to compensate for this in real time by
using a sum of the gases emitted. So far, just feeling for a way in the
almost-dark. Thanks for identifying the discrepancy and let's keep looking
for the reason. You can at least guess Siegert constants for the char based
on a guess at its chemical composition and report the difference it makes in
the final calculation. If it is greater than your measurement errors we have
something significant to talk about.

 

I have been having a very interesting time in Java talking to people using
stoves for 'industrial' purposes. We are going to have to redefine what
'domestic' stoves are! Rice hull is a widely available fuel and I have yet
to see a decent burner for them locally save a photo of an exact knock-off
of Roger Samson's Mayon Turbo Stove.

 

Here, in reply, is a simple test result for thermal efficiency on something
made locally. It shows how the thermal efficiency varies systematically with
power giving a policy manager valuable information about how it performs in
different circumstances. This was for one pot size only (large). Different
pots (and woks) yield different profiles and efficiencies at the same power.

 



The trend line is for both water heating and boiling.

 

 



The instantaneous efficiency values are provided for entertainment purposes
and are jumping around due to the (im)precision of the scale. The overall
efficiency of 23.0% is based on the overall mass measurement which is quite
precise (1 part in 450) so it meets (that part of) the IWA precision
requirement for Tier performance claims. The two charts are extracted from
the same set of data.

 

I wondered if the thermal efficiency was related to the water temperature
but have not corrected these thermal efficiency numbers for the power level
at the time. Here it is anyway:

 



The trend is for the heating portion only. It is too shaky to make a claim,
I want to see the power-corrected plot.

 

Regards

Crispin

 

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