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Post by Donkey on Mar 20, 2015 15:41:38 GMT -8
Today I called the business that makes those heat exchangers, talked to the guy for some time (nice man, interested in the project, tried to help with suggestions). Upshot of the conversation: those heat exchangers probably won't work very well for this application. The surface area of the pipes inside the exchanger is a LOT less than a reasonable copper coil and the added surface area of the fins isn't enough to compensate.
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Post by Donkey on Mar 18, 2015 12:39:22 GMT -8
Wolf, I noticed that and am sure it work anyway. What would the drawbacks be?
The water to water ones have SO little surface area, I doubt that they would be nearly as useful for this purpose. 60 feet of half-inch soft-copper costs around $200.. 2 of these is an excessively expensive heat exchanger.
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Post by Donkey on Mar 16, 2015 12:42:44 GMT -8
Sasha, your images are huge! For future reference, images that are intended for viewing on screen (web stuff, etc.) should be a MAXIMUM of 1000 pixels (dots) wide, your images are about 5 times larger. I've replaced the large images with smaller versions. OK, the project at hand. I think that if you are going with a batch-box, you can probably get away with a 6 inch model. If you were going with the J-tube design, I'd say 8 inch. The water barrel on mine is about 20 gallons, which seems like a good size. It heats up in a reasonable time and in one good heat, we can take 3 or 4 showers. My heat exchanger coil is 60 feet of 1/2 inch copper, which in retrospect seems a little small. At fully-on, it starts hot but then tapers off; if it is run at half strength, there is no noticeable tapering of heat. Tells me that the surface area of the exchanger is too little. I've been contemplating adding a second 60 feet of 1/2 copper next to (inside) the first. I calculate that my heat exchanger (the copper coil) has about 7.8 square feet of surface area. 50 feet of 3/8 inch copper is going to have less surface area yet, about 4.8 square feet. I think you will need much more than that. It seems to me that for the cost (or maybe a lot less) of enough soft copper pipe to do the job, you could get a different kind of heat exchanger that might work better. Something like this maybe.More later.
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Post by Donkey on Mar 15, 2015 19:38:18 GMT -8
I liked the "flowing around the outside of the hopper" one.. A double-skinned hopper with air flowing between the skins.
It could be built as a water jacket too. This would be a LOT more complicated, which is not my usual kind of thought form. Probably comes from talking to Ron over at Bigelow Brook Farm about his system.
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Post by Donkey on Mar 15, 2015 19:09:25 GMT -8
My solution to coal build-up has always been to wait a little while before adding more wood. The mass stove thing makes is easier to be patient in this way, I think.. Kind of a different mind-set, I suppose; Mass slowing down the heat, the inclination is to breathe a little; with lighter box stoves, I remember always rushing to cram in more wood quick, before the heat could slack on a cold night.
I noticed the oddly shaped P-channel too. What was the reasoning behind this? It obviously took a little doing, so there MUST be a reason. If it works, then it ain't broken so don't fix it. One possible thought is that if that piece of metal gets hot, it could prevent cool air from travelling down into the fire. Signs of that would be smoke streaming out of it and the possibility that it would be much easier to choke the fire by pushing all of the wood fully forward.
Nice beginning, carry on!
A lighter way to resize images ((in LINUX) if you don't want to deal with Gimp) is to use Gthumb. It has resize and rotate features, with batch-processing into separate folders and can be used while browsing images.
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Post by Donkey on Mar 12, 2015 7:13:20 GMT -8
Karl, you should write a book for the low-tech geopolymer tinkerer! Something light but informative and easy to follow. I'd buy a copy (or maybe even a case) in a heartbeat!
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Post by Donkey on Mar 12, 2015 7:08:56 GMT -8
When water turns to steam, it expands about 1000 (one thousand) times it's original volume. The pressure this can bring to bear outstrips any material that we (the common man/woman) can get our hands on. As long as that expansion has an easy place to go to, you've got no problems. Be aware that if you have hard water, boiling it in a tube will create calcium deposits on the inside of the tube, narrowing it. At some point, the tube may close entirely; then, you will have a problem.
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Post by Donkey on Mar 10, 2015 9:28:47 GMT -8
I think it's a little under-powered.. When I do this again, it's going to be either an 8 inch J-tube or a 6 inch batch-box. I'm contemplating turning this one into a batch box. Seems like a clever idea to me, the only real negative that I see is that the firebox will be down at ground level and the user will need to get down on hands and knees to feed it.
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Post by Donkey on Mar 2, 2015 8:07:06 GMT -8
One time I stacked a 12 inch J-tube out of firebrick.. It was ridiculous, just to look at the thing.. I didn't bother with lighting it or anything, just laughed at it, shook my head and kicked it apart..
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Post by Donkey on Feb 28, 2015 13:50:52 GMT -8
Depends on a lot of factors.. Seems that last summer the average was between 45 minuets and an hour or so. I think it should have been an 8 inch stove, rather than a six inch one.
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Post by Donkey on Feb 23, 2015 14:21:03 GMT -8
I believe there's a tile maker in Canada. Somehow, I'm failing to google her..
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Post by Donkey on Feb 23, 2015 11:04:23 GMT -8
In short, yes. But it's a thorny problem that will require a lot of thought and some compromise to pull off. Welcome!
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Post by Donkey on Feb 23, 2015 11:01:13 GMT -8
Bigelow Brooks pellet hopper is quite good, though he recently experienced a disaster with it. Alternately, you should read through the thread here.For the pellet/wood chip users, I think there is still some work to do to make a truly satisfactory feed/airflow system. I'm hoping to see more thought and experimental time put in on that score.. Remember to SHARE YOUR RESULTS!! Welcome to the boards!
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Post by Donkey on Feb 23, 2015 10:53:32 GMT -8
The hookah air scrubber has been tried. It was a fail! Not enough pressure can be generated by the stove to push through the water.
Daryl's got the right idea. Build the tin-can model, then build a 5 gallon can model, then do some project in the yard and grow it till it takes over your life and consumes your waking imagination!
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Post by Donkey on Feb 23, 2015 10:46:26 GMT -8
The beauty of this oven is that you can use it as it heats, at a range of temperatures; use it as long as you want at high heat while firing (maintaining heat); and let the fire go out and use it while it cools, at a range of temperatures. It's a thermal mass oven, so it will act like a traditional wood fired AND it can be stoked as it is used for, say, baking pizza for hours on end.
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