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Post by patamos on Jul 14, 2019 10:13:39 GMT -8
I wonder how much less 'push' the downdraft systems have? I know Matt's side drafting split riser set up benefits from a little more buoyancy in the exhaust flue to pull the gasses through a given harvesting mass.
Not to dis down-drafters, maybe they are great in this respect. But my guess is some extra resistance is involved. In all the discussion of combustion efficiency we often forget that in real world firing, optimal harvesting is no less important.
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graham
Junior Member
Posts: 74
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Post by graham on Jul 14, 2019 14:53:20 GMT -8
I presume that the down draft means more heat is radiated closer to floor just like a traditional wood burner.
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Post by patamos on Jul 14, 2019 17:28:16 GMT -8
Ya that makes sense. But i am referring to the drag on the flow of gasses through the system caused by pulling hot gasses downwards when they naturally want to rise upwards. It may not be a major factor. Just wondering if anyone has info on this
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ukdan
New Member
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Post by ukdan on May 8, 2020 22:36:16 GMT -8
Peter have you ever tried a secondary chamber underneath? A heater like the Walltherm need to be heated up in updraft mode for half an hour in order to create enough draft. During this heating up it burns as clean or dirty as a bog standard box stove. My goal has been a system that burns clean within 5 to 8 minutes, no more. This way the clean burning period in every run is as long as possible. Long ago I tested a Walltherm, twice. Maybe I could take this discussion to a new thread and dig up the results? Hi Peter Did you ever create a new thread about your downdraught testing? I'm a big DSR2 fan nowadays and am working on a stove for outdoor use as a hobby. Many years ago I nearly bought a Walltherm as my main home boiler but I didnt go through with it as the full costs (with ~1200litres of water storage, plus controllers etc) was not a sensible economic choice.....for me. At the time, I could not find any emissions data for the warm up phase so I did have a few lingering doubts too. Nevertheless, I'd love to see and discuss any downdraught data that may be around. Thanks Dan
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Post by peterberg on May 9, 2020 2:38:08 GMT -8
Did you ever create a new thread about your downdraught testing? No I didn't, mainly because it seemed to complicate building one such device. In theory it could probably be done, for instance a chamber underneath the normal firebox and a port in the rear wall of that. There should still be a riser behind it and secondary air provision need to be done in a completely different way. How to do all this and to cram the whole of it in a simple to build heater might be another year of development away. The main problem is how to create enough draft in the system in the first stage of the burn. Otherwise there won't be downdraft at all, it need to be a self-starting system to some degree.
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Post by ahansen on Jun 3, 2020 14:55:18 GMT -8
little boost: if the chimney is closer to the core it would already be a bit warm from last fire. maybe the chimney on top of fire box with som kind of (self closing...) draft door direct from fire box to chimney closing when chimney pulls enough to take the down draft
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