[Stoves] Temperature datalogger

Julien Winter winter.julien at gmail.com
Wed Sep 17 15:39:19 CDT 2014


Hello Roberto and stovers;

I can't say whether the Pax temperature datalogger is accurate or durable.

However, I am using a four-channel Omega Insturments HH1384 datalogger with
TJ36-CAXL-18U-12-SB-SMPW-M thermocouple probes.   To date, I have over 90
runs, and it is still working very well.

I am in the middle of a study on fuel bed temperature of a natural draft,
top-lit updraft gasifier.  Provisionally, I am finding that for wood
pellets and chips, the pyrolytic front is between 500 to 750 °C for very
low to high primary air, respectively.  The main effect of turning down
primary air is to slow down the velocity of the ignition front.
 Interestingly, with wood chips there is an increase in channeling down the
sidewalls as primary air is reduced.  The more channeling happens, the more
likely (I believe) that some of the wood chips pyrolyze in the absence of
oxygen.  Channeling doesn't seem to be a problem with wood pellets.

When sticks of 1 to 3 cm diameter are the fuel, the temperature in the fuel
bed can go as high as 900 °C.  I suspect that this is because with large
pieces of fuel, there can char combustion on the surface of the fuel
particles while pyrolysis is still proceeding at a lower temperature in the
interior.  At low primary air, channeling of the fire can also occur in a
bed of sticks.

I will post on the Stoves list the results of my investigations in a couple
of weeks time.

All the best,
Julien.


-- 
Julien Winter
Cobourg, ON, CANADA
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