Alex English (Dec 18/97)
Check out a Thesis by Grant Ballard-Tremeer which promotes the use of vent hoods for the testing and evaluation of rural cooking stoves. http://www.ilink.co.za/~grantt/
After reading his thesis I was motivated to try and apply it to the testing of the One-Can Charcoal Making stove.
The stove fits inside the cut out oil drum. A short length of pipe on top leads to a small, high temperature, fan which provides just enough draft to capture all the combustion gasses. This was only clear to me when the stove lost flame and billowed smoke which did not come out the side opening. The draft showed very little effect on a flame held at the top of the side opening.
To determine the flow rate I measured the time it took to fill about 8 meters of a 15cm diameter tube. The fan with this set up could move about .57 m3/sec. This is about 5 or 6 time the volume of air used by the stove. This facilitates continuous sampling with my CO meter due to the lower temperatures of the gasses. It also means that during periods when CO concentrations rose they were still below the tools limit of 2000ppm.
Previously I had been taking samples from inside the stove at pot level with no assurance that the emissions were consistent on all sides of the shielded pot.
Most important for me is that I can now, by hooking up this fan to a chimney, isolate the emissions from my own lungs. This device will now ocupy a tiny corner of a heated room where tests can be made during the winter sheltered from finger freezing ambiant temperatures.
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