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Post by satamax on Apr 9, 2013 12:56:26 GMT -8
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Post by pinhead on Apr 9, 2013 13:07:31 GMT -8
That's a perfect example of a bell, though I suspect with such a large area the heating would be a bit uneven.
Great. Now I'm going to have dreams of building a 14-inch Petersberg stove to feed this huge bell... ;D
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Post by Donkey on Apr 9, 2013 14:27:21 GMT -8
 Yep, me too.. Interestingly, there are traditions of underfloor heating all over the world. In Korea , it's called the Ondol. On a more manageable scale, the Kang bed, from China.. Basically, a cob/stone layered bench/bed. Neat historical factoids.. An historical factoid that's maybe NOT so neat.. Apparently, the Romans wrote about hypocausts failing, cracking, leaking noxious gasses into the home/bathhouse and killing people. This fact didn't lessen the demand for hypocaust floors, simply everyone who WAS anyone wanted one... |
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Post by pinhead on Apr 9, 2013 18:50:36 GMT -8
Yep, me too.. Interestingly, there are traditions of underfloor heating all over the world. In Korea , it's called the Ondol. On a more manageable scale, the Kang bed, from China.. Basically, a cob/stone layered bench/bed. Neat historical factoids.. An historical factoid that's maybe NOT so neat.. Apparently, the Romans wrote about hypocausts failing, cracking, leaking noxious gasses into the home/bathhouse and killing people. This fact didn't lessen the demand for hypocaust floors, simply everyone who WAS anyone wanted one... I was kind of thinking they could be quite dangerous if the floor ever cracked. OTOH, if there was enough "left over" heat for a tall, extremely well-insulated chimney, shouldn't the entire sub-level be under a slight vacuum (such as in our smaller bells) once the stack temperature rose above outside ambient temp? I don't see any "stacks" and with that big, open arch it looks like they just threw wood in and lit it up making for a smokey, inefficient, noxious gas-producing burn. |
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Post by satamax on Apr 9, 2013 21:32:03 GMT -8
Guys, about the cracking, we have better materials than the romans.
I was thinking about a massive J tube, with the feed flush with the ground. Fited into a prestressed T beams and blocks floor. Something like a two or three inch slab poured onto this. I was talking about this with the guys at permies. Someone started talking about insulation. Tho, is it realy needed? Due to the convection in the flue gasses, the bottom of the bell shouldn't be heated. May be the sides could be insulated thought. A little straying could be using a hole in the floor, and fiting the whole J tube in it, with a gap on the sides which would serve as a barrel gap. Well, many ideas, and nowhere to put theses to good use.
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Post by Deleted on Apr 10, 2013 1:48:13 GMT -8
Guys, about the cracking, we have better materials than the romans. We like to think so. But is it realy true ? Pozzolan-lime cements used by the Romans can be very strong. Some buildings still exists. None of our high tech buildings will exist after two thousand years. The Egyptians used cement in around 2,500 BC. The oldest known surviving concrete is 3000 years older. |
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Post by redmohawk on Apr 10, 2013 15:36:47 GMT -8
In its time it was most likely the easy option , lead pipes were avalable along with clay etc but heating the floor in such a way was prob the best/easyest option.
Now we can heat the water/room without needing to risk issues with "Co" issues in such a way.
Though with a little well thought out planning I'm sure a few cracks would be of little consaquence , with a good draft from a well setup chimney/bell setup I'd be under the assumtion a negitive pressure would remain in the bell able to cope with minor leaks.
Why you would take the risk is the question, when other safer ,cheaper ,and probably more effecient option are now avalable is the question.
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Post by Donkey on Apr 10, 2013 22:44:55 GMT -8
Another interesting factoid on Roman hypocausts:
They often incorporated flue tiles into their walls, so that the heat would flow from under the floor through the walls in MANY places.
Their flue tiles were quite small, no single flue in the building could carry all of the load. As a consequence, the pressure differential was VERY slight, difficult to measure even with modern equipment.
It's likely that the extremely low draft, coupled with crack prone floors caused the problem.
Still, hypocausts were VERY popular. A few deaths didn't slow demand much..
Kinda like us with our cars.
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Post by kwillets on Apr 11, 2013 20:03:14 GMT -8
Here's the best reference on Ondols that I've found: home.snu.ac.kr/Html/ondol/1.htmChapter 5 has a lot of design diagrams, many labeled in English. CO poisoning can be a problem, so the floor design specifies layers of plaster and oiled paper to block gases. An extra chimney can help, but I think most CO poisonings occur when the stack effect is diminished as the fire dies down. |
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Post by aparker on Jun 12, 2013 9:56:46 GMT -8
If the end of the burn is the problem, you could design in a bypass and isolate the fire from the bell when it is down to coals. I saw a modern ondol on the internet with a draft inducing fan on top of the chimney. On PBS's Nova they built a Roman bath in Turkey with a hypocaust: www.pbs.org/wgbh/nova/lostempires/roman/builds.htmlThe hypocaust was not a bell in the sense that has been discussed at this forum because the chimneys did not start below the level of the inlet. I would be interested to see someone experiment with a large squat hypocaust-like bell with multiple small diameter chimneys. I wonder how the flexible membrane that is used under tile in showers and wet bathroom floors would hold up to heat? |
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