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Author Topic: Can we pull heat from the ceiling with materials that shrink when heated?  (Read 4770 times)

Offline McKay

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Can we pull heat from the ceiling with materials that shrink when heated that are suspended in a carefully chosen fluid in which the material (like Zirconium tungstate) floats when at the temperature of the floor, but sinks (shrinks - gets denser) when at the temperature of the ceiling? That is, ceiling is usually quite a bit noticeably warmer than the floor, due to the fact that hot air rises.
If a material would sink to the floor level when heated, absorbing the heat energy from the ceiling, then rise again, when cooled a bit, giving the heat energy to the floor level (perhaps pipes under the floor) and expanded, that would make a passive system that puts the heat where its most needed, instead where it wants to go, wouldnt it?
(I am talking about about houses in the kind of climate where we would actually want to heat our houses, of course)


 

Offline alancalverd

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Neat idea, and the anomalous convection of water below 4 deg C accounts for a lot of natural phenomena. So the question is what fluid could you use that will float zirconium tungstate? Problem here is its density is around 5 g/cc  so you would need to package it into a just-floating pellet with some buoyant material whose coefficient of expansion is negligible.

There are plenty of heat-recovery airconditoners that take hot air from the ceiling and use it to preheat fresh incoming air, but they still require some energy input.
 

Offline McKay

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Sure, I know that fans can be mounted to pull hot air from the ceiling. But I like to be prepared and dont like to be dependent on the electric grid. Sure, solar panels and wind turbines, which I will want to install eventually, if money allows, but the more backups and independent systems, the better :D
I was first thinking about getting the required electric energy for the fans from the fireplace, that is the main heating source in the house, using temperature difference,  but then I thought if the energy from that would be enough and - could there be a even more passive system? (inspiration from lava lamps)

Zirconium tungstate is just the first such material I found in google, it doesnt have to be it. And I dont know if the right material combination can be found and actually be practical, but that why I ask here :) Just a thought I had.

 

Offline alancalverd

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I have a couple of fans driven by thermoelectricity, that sit on top of my woodburning stove. They certainly improve the distribution of hot air from the stove, with no external power source. If you wrap your chimney with thermocouples you can probably generate enough electricity to power a substantial ceiling fan to recirculate the hot air over a large area.  A small woodburner will be producing about 5 kW of heat, of which at least 20% goes up the chimney, so why not use it?   
 

Offline McKay

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Sure, sure, but I am wondering about this idea, because, well, fun ! :) and, potentially, might better - passive, less things to brake down (fans with their motors)
« Last Edit: 13/04/2015 19:23:04 by McKay »
 

Offline wolfekeeper

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If you could do the zirconium tungstate thing then you could keep a pool of cold water underground and plumb down to it; it would act as a huge thermal mass and even out the internal temperature, completely passively.

I don't know if it's practical, but Archimedes divers might work if you balanced them, and filled with the stuff maybe.

edit: Maybe you could play games with relative expansion coefficients. If you have some oil which expands a lot, and something floating in it that expands hardly at all, it should set up the same effect.

edit2: you could do much the same thing with a low pressure steam engine. If you had a low pressure boiler type thing on the ceiling, then when the radiator heats up the water in it, if it's at the right pressure, it will boil at 20C or so, and then the steam will then force its way through the piston engine down to the second radiator at ground level, where it will condense. You run a small 'makeup' pump powered off the steam engine to refill the top boiler with more water from the bottom radiator through a float valve. It should be pretty quiet, and only very slow pumping- water has a huge heat capacity.
« Last Edit: 13/04/2015 22:53:22 by wolfekeeper »
 

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