[Stoves] heat transfer, radiation, etc.

[Dean Still]

Hi Frank,

 

Ernestine has finished the paper on fuel use, emissions, moisture content.
If I remember correctly the middle value for moisture was best. I'll write
Ernestine and see what's up.

 

Up to plus or minus 50% of the heat can be captured. Combustion efficiency
plays a smaller role in decreasing how much wood is used for cooking because
even smoky fires turn about 90% of the wood into hot gases.

 

I look at the following to increase stove efficiency:

 

Increasing radiation to the bottom by decreasing distance, encouraging flame
to raise temperatures in the fire, radiation is temp. dependent.

 

Temperatures of hot gases to the bottom of the pot should be above 500C
hopefully more like 600-700C if everything is running ok.

 

Make stove top to maintain equal cross sectional area under the pot bottom
or even decrease a bit if the combustion is clean. This greatly improves
heat transfer by convection.

 

Use a pot skirt, even a short one (10cm high), that creates a small channel
of around 10mm up the sides of the pot to get 60-70% heat transfer to the
sides.

 

Use a pot with a big bottom and small top or use a pot with lid. Heat loss
from pots is largely from evaporation.

 

Clean up combustion, for sure.

 

Keep temperatures high in combustion zone by using insulation. Establish an
appropriate fuel/air ratio. Get mixing to happen of gases, air, flame. Meter
the fuel...etc., etc.

 

That's a large part of my mental checklist when I'm trying to figure out how
to get a stove to run better...I've tested Chinese stoves that shoot steam
into the fire. It did not decrease fuel used but did decrease emissions, I
think because of more mixing.

 

All Best,

 

Dean