[Stoves] flames touching pot
Crispin Pemberton-Pigott
crispinpigott at gmail.com
Sun Sep 11 23:25:22 CDT 2011
Dear Paul
>But if the secondary air is hot as it enters the burner and if there is not
too much of it,
should there not be a relatively high flame temperature from such a blue
flame?
There can be a high temperature. That does not mean it will be, of course.
The greatest enemy of temperature is excess air which directly impacts heat
transfer efficiency. The heat transfer efficiency of a crummy stove (one no
better than an open fire) can be tripled by perfecting the excess air alone,
with no change in combustion efficiency.
In the case of your present stove and the central fire prototype you should
test it with a pot on, because it will be very different. In fact the flame
temperature is not a particularly good measure of a stove because if it is
really hot in one spot, and cool 15mm away from it, there is nothing one can
know about how it will perform. As a thermocouple in a flame is only an
indicator, not a meaure of flame temperature, it rapidly becomes an academic
exercise.
Something helpful is the temperature of the gases just after the flame
finished burning, and at the gas exit where the gases move into the open air
away from the pot (at the exit point with no ambient air diluting it). That
is also a good place to measure the excess air and CO/CO2 ratio because from
those number you can calculate the system's heat transfer efficiency and CO
mass emitted without using a hood.
Regards
Crispin
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