[Stoves] Percent char possible

[Julien Winter]

Hi All;

All the mass values in the "Basic Operating Parameters" pdf are on a dry
weight basis.  This factsheet was limited to two pages, so many details are
left out.

A couple of extra pointers about Figure 2:

1) The reason the relationship between char yield and maximum temperature
is linear is because lower char yield meant that char had been combusted,
with a directly proportional release of heat.

2) The thicker the fuel, the more char was combusted than with thinner
fuel.  This is  because it takes longer for the center of thicker sticks of
wood to reach pyrolysis temperatures than 5 mm thick wood pellets or wood
chips.  Whilst the center is heating up, char is being lost at the
surface.  Fuel-dry wood is not a great conductor of heat, and the surface
can be 750 °C while the center is still 25 °C.

What I need to do is to find the ash content of the fuels so that I can
express some of the values on an ash-free basis.  However, the intent of
the factsheet is to provide numbers that anybody can measure with a simple
digital balance.

The research could also benefit from knowing the superficial velocity of
primary air, rather than grate aperture.  Again, grate aperture is
something that everyone can relate to.

Cheers,
Julien.

-- 
Julien Winter
Cobourg, ON, CANADA
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