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Current Heater Testing at Lopez Labs

February 26, 1997

(9:50 a.m)

Our new technician, Clover Ardern, has done a baseline series of 20 test runs with fairly random wood loads on a 22" Heat-Kit heater with bakeoven.

Next, we did an 11 run series with a controlled wood load. All pieces in a given run had the same moisture content, and are split from hardwood boles between 8" and 14" in diameter. The most recent test that is online (with links to previous tests) is the 8th run in the series, Run HK-f29

Yesterday, we started a new test series with a modified air inlet. The inlet has an adjustable jet plate that uses the strong draft available at the end of the burn, combined with a small air requirement, to create extra turbulence for burning the charcoal faster. Today, we were able to debug it a little further, but were unable to make the planned air adjustments at the end because of a technical problem. Nevertheless, we are seeing less excess air and 2 - 3% higher overall efficiency compared with the 11 run baseline.

We experienced some calibration problems with the oxygen analyzer yesterday due to temperature swings in the lab, and are now ensuring that the analyzer has a temperature-stable environment and keeping a daily calibration log.

Today's wood load consists of 9 pieces and 2 lb kindling. The pieces are stacked in a 3-2-2-2 log cabin configuration. The rows are stacked tight, with the bark down (see fuel load photo).

We used a Kodak DC-50 digital camera to document the burn progressions. Below are the images from today's test run, which finished at 11:00 a.m. Downloading the images from the camera, processing them, and uploading them to the server takes about 45 minutes.

It is a little early yet to start drawing conclusions, but our basic thesis is that wood sizing and stacking has as large an influence on heater performance as any other factor, including heater brand.

We have not really looked seriously at the air supply yet, because we want to be able to separate out the fueling effects first.

RUN No. HK-f34
Number of Pieces
Total Weight, lb
Wood Moisture %
Fuel Surfac/Vol


Average Stack Temp, F

+/- 0.1

Average O2 %

+/- 0.2

Stack Dilution Factor
g/kg CO
Combustion Efficiency %
Heat Transfer Efficiency %
Overall Efficiency %

+/- 1.5

Average Output, 24 hrs, Kw




Click on thumbnails below for larger image. The set of thumbnails is also repeated vertically, below, with descriptions attached.

2 minutes
Kindling is piled left to right in front of pile.
Fire has a slow, smoky start.
With the new air supply, too much air is blowing onto kindling
5 minutes
Fire catches and smoking stops.
10 minutes
Air jet is reduced 1/4" at 12 minutes
15 minutes
20 minutes 
Very brisk fire
Oxygen bottoms out at 9.2%
Stack temperature is 409.4 F
25 minutes
30 minutes
At 38 minutes, air jet is reduced a further 1/4"
40 minutes
Spacing in pile is getting quite open
Pile is poked at 47 minutes. See next image.
50 minutes

60 minutes
Pile fell at 63 minutes
Fire poked at 65 minutes
See next image
70 minutes
80 minutes
Interrupted by phone call.
Test finished by technician without further intervention
90 minutes
100 minutes
110 minutes
120 minutes 
0 minutes

This page last updated on April 9, 2003
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