[Stoves] Measuring Temporal Changes in TLUD Burner Heat Flux

[Crispin Pemberton-Pigott]

Dear Julien

Taking only your last point, if the heat transfer efficiency is known, the heat gain known continuously and a known mass change, can be, particularly late in the burn, be translated into an understanding of what is burning. This would be very helpful for analysing TLUD's.

More later of the signal delay and quantifying and correcting experimental and systematic errors...
Crispin

Hi Crispin;

A water heat exchanger is a reasonably inexpensive option
(
http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/2015-June/010408.html
)
 but I expect that there is a bit of a lag in responsiveness.   I think it
will be important to make sure that the mass of water is as small as
possible so that the rig is responsive to changes in time and magnitude.

I have been looking into heat flux sensors, such as the one sold by Huksflux
http://www.huksefluxusa.com/HF01.php?pSection=heatFlux
That is a more expensive option at $5,600 CDN not including the data
logger.  If a heat flux sensor was used, it would have to be calibrated
against heating water in various pot geometries.

The above sensor has a maximum operating temperature of 800 °C, and a
ND-TLUD running on a reactive bed of fuel could surpass that.

Since in the course of pyrolyzing a batch of fuel, the power output of a
ND-TLUD can decrease, characterizing the temporal profile of energy flux is
more informative that water-boiling tests, because water-boiling is only an
average.   A change in energy output from a ND-TLUD may affect the
interpretation of its turn-down ratio.

I suspect that the decreasing power output from a TLUD is caused by
diversion of some pyrogas to secondary char as the height of the char bed
increases.  The power decrease is greatest when primary air is greatest,
and the char bed is hottest.  The power decrease can be small to none if
the TLUD is run at its lowest primary air setting.

Cheers,
Julien.

--
Julien Winter
Cobourg, ON, CANADA
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