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Post by mscantrell on Oct 16, 2014 10:32:27 GMT -8
These are limited to the melting temperature of the pipe, right?
You couldn't stick one into the hot part of the heat riser without melting the copper?
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Post by Donkey on Oct 16, 2014 12:24:23 GMT -8
I wouldn't do that anyway.. Never take heat from the heat riser itself, always wait till just down-stream of the heat riser outlet at the earliest.
To actually answer the question, I don't really know that. The pipe is moving heat very efficiently and spreads the heat totally evenly all the way down, from end to end. I suppose that, left long enough the pipe could rupture and then melt or just get hot enough to melt without rupturing.. I suppose anything is possible down the extreme end of things.
If it turns out to be practical, I would place one end down into the first few feet of bench, or inside of a bell, take the other end upstairs to heat a space above and insulate the middle as well as possible.. Something like that.
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Post by mscantrell on Oct 16, 2014 17:36:39 GMT -8
Right, you wouldn't want to rob heat from any spot where combustion is still happening. I just meant to express, a spot that's much hotter than the melting point of copper. But you're saying, you think the coolth of the room might be enough to keep the hot end from melting, even there? Fascinating. I'm picturing a little copper stub coming out of the wall of the heater horizontally, then turning downward for a couple inches. So you could put a pot of water onto and boil it by immersing the stub.  |
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Heat Pipes
Oct 16, 2014 21:00:37 GMT -8
via mobile
Post by ronyon on Oct 16, 2014 21:00:37 GMT -8
Could one be made to include a radiator?
I am thinking of one end in a thermal mass and the other in the return air duct of a forced air furnace.
Insulate the crap out of the mass, heat it when convenient, when the furnace kicks on you preheat the forced air.
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Post by Deleted on Oct 17, 2014 2:55:02 GMT -8
The gas coming out of the riser is very hot,
but the energy density is very low compared
to a solid or liquid of the same temperature.
The corona of the sun is in excess of 1000000°C,
but within the corona someone would rather freeze to death,
than be roasted.
If the heat can be moved away faster than
it can be delivered by the hot gas the hot end
of a heatpipe can not become significantly hotter than the cold end.
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Post by photoman290 on Oct 17, 2014 3:06:29 GMT -8
is that a variant of the party trick of boiling water in a paper container?
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Post by Deleted on Oct 17, 2014 3:40:26 GMT -8
Yes, the party trick works because the heat
is moved away faster than it can be delivered.
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Post by Donkey on Oct 18, 2014 10:52:33 GMT -8
I did the experiment with 1CC of water and I think that it was not enough. I left the pipe sitting in the sun for most of the day, then heated the entire pipe with a torch to drive away the last of the moisture (accidentally de-soldered the bottom cap, had to redo to insure it worked). With the pipe completely dry and still quite warm, I injected 1CC of water, heated as above and capped it off tight. Testing with hot water, heat travelled a short distance up the pipe and stopped entirely. My assumption is that there was not enough water for return/recycle. There was almost certainly some loss when heating, though no way to know how much. So, I decided to try again in a different way, perhaps a bit less scientific. I overfilled the pipe, shook it well to wet the entire inside, poured out what would pour out easily. Now, assuming that the inside was fairly well coated with droplets and/or generally wet, I heated (as before) and sealed. This one works pretty well. I haven't been timing heat movement in the pipe (though it seems obvious that I should) but I would say that it takes a bit more than a solid minuet for heat to move all the way to the top. Immediately after placing the pipe in hot water, I place my hand around the middle of the pipe and can feel heat moving up. It quickly gets uncomfortably hot, so I slide my hand up, keeping in the warm zone and moving when it gets uncomfortable. In this way, my hand is in constant motion, moving at the rate of a child (curtain climber) crawling with purpose. I think I'll try a smaller pipe next. |
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Post by Deleted on Oct 19, 2014 4:01:45 GMT -8
One minute is far to long.
Though the mass has influence too.
How thick is the wall ?
Pipes needs to be very clean, remove any fat or oxide.
The complete pipe nedds to be above 100°C.
For thicker tubes solder or weld a plug with a small hole,
which can be closed very fast.
A friend used hollow rivets to close the small hole and then soldered hard.
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Post by photoman290 on Oct 19, 2014 6:08:02 GMT -8
i thought of using compression fittings with a blanking plug. you can get a thick brass washer with a taper on one side which fits under the compression fitting nut. that would be a very quick way to seal the end as you only need a quarter turn to seal it. you could solder it afterwards if needed. not sure if compression fitting will hold a vacuum but they hold 10 bar ok so i dont see why not. i know that is not true for tanks though.
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Post by Donkey on Oct 19, 2014 20:35:48 GMT -8
One minute is far to long. Though the mass has influence too. How thick is the wall ? Pipes needs to be very clean, remove any fat or oxide. The complete pipe nedds to be above 100°C. For thicker tubes solder or weld a plug with a small hole, which can be closed very fast. A friend used hollow rivets to close the small hole and then soldered hard. The pipe is thick walled, 3/4 inch copper that has been sitting around for a long time. It's bent, dented and likely rather dirty inside. I'm going to use some 1/2 inch stuff that is quite a bit cleaner. I think I'll figure a way to clean it out before I start. It also makes sense to use distilled water (which I have NOT been using). Perhaps in a day or two. |
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