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Post by patamos on Oct 13, 2016 9:24:14 GMT -8
Thanks twd, Yes those are all valid factors. We've been discussing the matter recently on another thread 'a question for the experts.' My line of thought is that the smaller slower fire of 'burn-on-demand' metal box heaters must send a higher ratio of the generated heat up the flue to sustain optimal draft. Assuming excess air is a constant, a 1000c fire with exit temps of 80c will have about 20% greater harvesting efficiency than a 500c fire with 80c exit temps. I see four major factors in overall efficiency. 1 - combustion, how thoroughly are all the gasses being extracted from the wood and converted into heat. 2 - harvesting, how much of that heat is made available within the dwelling 3 - utilization, how much of that heat is warming our bodies (without creating unwanted atmospheric convection loops) 4 - operation, how easy is it to load and adjust when necessary. PVDB batch box excels at 1 and 2, can do so at 3 ( especially if you build a mass bench into it), but (presently) loses points at 4 due to a small fire box door low to the ground the Vortex and various masonry heaters are a bit less effective at 1 but more effective at 4. Some people are happy with this trade off. So the question comes down to: How much wood is being burned to achieve a desired level of comfort? If at the end of the day comfort and good health are what matter most, then the value of soaking up far-infra-red heat from a conductive bench is not to be under-estmiated. Factor 3 is thus the key element that sets mass heaters above the rest. my two bits worth
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Post by ericaus on Oct 13, 2016 13:11:19 GMT -8
I've just been going through AS 4012 ( www.dropbox.com/s/hz3i1ldtbtx63ct/4012-2014%28%2BA1%29.pdf?dl=0 ). This Australian Standard describes the procedural methods for determining the efficiency of wood burning heaters.It focuses on Joules in versus Joules out. The heater under test is set up in a calibrated calorimeter room and even uses an oil bath around the flue to reduce heat loss through conduction. It does exclude masonary (and rocket mass ) heaters. I'd be interested to hear what the protocol was at the decathalon.
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Post by matthewwalker on Oct 13, 2016 13:30:15 GMT -8
EPA Method 28, with some minor changes made for the masonry heaters in the warm up protocol.
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Post by ericaus on Oct 13, 2016 13:50:17 GMT -8
Thanks Matt. I'll check that out. I would have thought that if a calorimeter room wasn't involved that radiant heat energy from the individual heaters could not be compared or measured. Would this have been addressed in some other way? Edit: I just had a quick look at Method 28 and it seems that the focus is on particulate emissions and not so much to do with heat output efficiency. I would imagine the two to be mutually exclusive. What do you think?
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Post by matthewwalker on Oct 13, 2016 14:51:21 GMT -8
Testing was done via a Testo 330-LL with the particulate measuring option, and a comparable, uh, other manufacturer's unit. They measured both efficiency and emissions.
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Post by ericaus on Oct 13, 2016 17:24:10 GMT -8
I would have thought that testing for the burn efficiency would not necessarily be correlated to heat output efficiency.
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Post by matthewwalker on Oct 13, 2016 17:52:22 GMT -8
The machines measure efficiency in terms of heat from the fuel into the space.
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