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Post by mscantrell on Feb 26, 2015 6:40:34 GMT -8
Good morning!
I believe I saw the answer to this somewhere in the two long threads, but I'm not certain.
I recall that we determined there were two "modes" to run a batchbox:
either
1. "wide open", with unlimited primary air or 2. "controlled", with primary air supply being given in proportion to the rest of the system size.
And they worked equally well? Am I remembering that part correctly?
So. When running "wide open", do you still improve performance by adding a P-channel (or, now that a few other preheated secondary air delivery methods have been worked out, any of them?) Does secondary air still add any value in the presence of unlimited primary air?
Thank you, guys!
(For context, I'm mulling over my design ideas for this summer. My criteria are cost, ease of building, and performance, in that order. I'll be swapping out a 120-year old woodstove (yes, really) for this masonry heater, so I'm expecting a huge step up in performance, no matter what I build. So I'm willing to build something somewhat suboptimal, something somewhat less than state-of-the-art, if it will be cheaper and easier. My question here about primary air comes from considering door hardware. I can weld simple things, and I can do some forging (for hinges, etc), so I'd really like to build by hardware from scratch. Big difference in building a solid door or a door with just a window, vs. a door with two adjustable air inlets.)
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Post by Deleted on Feb 26, 2015 7:59:16 GMT -8
Aside of providing preheated air any kind of secondary air will significantly lower the speed of gas in the box and thus lower the amount of fly ash carried along.
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Post by DCish on Feb 28, 2015 6:29:28 GMT -8
To help with an answer to this, can you define "unlimited" primary air?
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Post by peterberg on Feb 28, 2015 9:39:52 GMT -8
Hmmm... Even with no door at all, the p-channel will still draw some air. By doing so, it will limit the main air stream slightly. The fire will burn, but it's not recommended to load it more than half full because of smoking back. Besides that, open fire is a hazard so you won't be able to leave the heater running unattended.
With a door of some sort the temperature inside the firebox will rise dramatically, the excess air figure will go down and the efficiency will go up, a lot. When in this state, opening the door in one go will cause all smoke break loose.
Try to think of a door without an air inlet which you can open just a crack and lock it in that position. This construction is not as effective as the inlet low in the middle but it will work. In that case only the p-channel would need a valve. And as a bonus the risk of flying sparks is limited.
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