Purely-Radiant Cooling

Hi:
I thinking of a cooling mechanism for houses and building in which the cooling -- in the direct sense -- involves only radiation and no convection at all. Sorta like a radiant-stove-top in reverse. Indirectly, however, some amount of convection and conduction will be needed [liquid nitrogen/helium, cold metals]. The cooling panels are on the ceiling and walls.
My visualization is that the radiant cooling panel contain extremely cold metallic coils [cooled by liquid nitrogen and/or helium], this would probably be deepest part of the panel.
Layer 1: a material that allows heat radiation to pass through but is a very poor conductor of heat Layer 2: the same material found on the very top of radiant stove tops Layer 3: this is the deepest part containing the cool metallic coils. Inside these coils are where the liquid nitrogen/helium would be flowing through]
Sorry is my visualization is vague, I myself am getting confused by it.
Can anyone think of a more efficient way for direct radiant cooling?
By direct radiant cooling, I mean that if you place your body at a noticeable distance from from panel, you'll feel cold because the extreme cold of the coil will draw IR radiation away from your body. OTOH, if you touch the panel, you won't feel as cold because the 1st layer of the panel is a very poor conductor of heat.
Thanks a bunch,
Radium
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How are you going to deal with the condensation and the resultant water runoff??
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and what if the kids are already pole lickers? you'd need tongue defrosters.
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I don't know, that's why I'm asking about this theoretical cooling device in these NGs.
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wrote:

Thats fine, but please consider that if your theoritical cooling device worked without having humidity and condensations problems, then everybody would already have one. Think radient floor heat, and then what is gonna happen if you try reverse it and cool the floor.....its gonna get real wet.
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So would this cooling device world best in low humidity -- so that there is little condensation?
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Green Xenon [Radium] wrote:

Why, yes, but you also need low CO2, low oxygen and low nitrogen in the room "air". What you are descibing, actually, is called a "cryopump". It will end up condensing not only the water in the air, but ALL the air! CO2 will freeze onto the coils, and Oxygen and Nitrogen will condense and drip onto the floor, thereby making puddles of liquid nitrogen and oxygen on the floor. Since the nitrogen will just be cooled to saturation, it will disappear immediately, leaving puddles of liquid Oxygen behind. If you have anything but ceramic floors, such as hardwood, vinyl tile, etc. you will likely have a violent explosion rather quickly. Liquid oxygen is basically gaseous oxygen compressed 1000 x, and therefore an extremely powerful oxidizer.
Why cool something to 77 K to cool off a human body at 310 K. Aside from the safety aspects of having something so dangerously cold around, it can't be efficient. And, you won't get your purely "radiant cooling", there will be HUGE sheets of insanely cold air falling off the cold plates and collecting on the floor. Within minutes, the room will have a thermal divide, with totally frigid air from the floor to the bottom of the cold plate.
Jon
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Ok. What if the CO2 and water-vapor are removed as completely as possible and the nitrogen & oxygen are repeatedly re-circulated and heated to at least 70 Fahrenheit upon recirculation? Convective heating prevents the N2 and O2 from liquefying. Would this help?
I know it's ironic that the air would have to be heated in order to assist in preventing the radiant cooler from failing. Still interesting, though.
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wrote:

My visualization is that the radiant cooling panel contain extremely cold metallic coils [cooled by liquid nitrogen and/or helium], this would probably be deepest part of the panel.
Another important fact. Remember in my 1st message:
The radiant cooling panel is the ceiling. It has 3 layers.
Layer 1: a material that allows heat radiation to pass through but is a very poor conductor of heat Layer 2: the same material found on the very top of radiant stove tops Layer 3: this is the deepest part containing the cool metallic coils. Inside these coils are where the liquid nitrogen/helium would be flowing through]
Layers 2 & 3 don't have any air molecules around them. The cold metal coils are in a vacuum so they are not exposed to any air that would solidify/liquefy.
About using nitrogen. I change my mind. I think it's better to use helium. Extremely cold liquid helium.
http://en.wikipedia.org/wiki/Liquid_helium
Here, another question arises. Which is better to use -- Helium-3 or Helium-4? Which one would have a stronger cooling effect if both were at the same temperature?
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wrote:

It is not theoretical
If you live in a humid place you are going to need dedicated outside air units, and dehumidifiers.A disaster waiting to happen in my opinion, if a system goes down you will have an indoor rain maker.
Not a rain maker because the surface of the panels is cold engough to make conditioned air sweat as the panels will be 60 something degrees, but cool enough if the ventialtion system went down, the humdity in the ventialtion air would make it rain.
They use it in europe, one internet guy uses it a fair bit in the pacific nw, you can use it in hospitals - you are not blowing germs around.
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To solve the wetness issue, the air in the room can be de-humidifed.
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wrote:

Which defeats the purpose in the first place. Air conditioning is 90% humidity control, and 10% temperature control.
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My idea is to have the dehumidification separate from the cooling.
Dehumidification is done by air processing devices on walls -- left, right, back, front. These walls give out and take in air. There is both re-circulation and fresh air. For fresh air, all vapors molecules are let into the room excluding H20. For re-circulation, air in the room is sucked, dehydrated and then blown back into the room. In either case, the amount of air-molecules-per-second-per-square-meter that is sucked out of the room is the same is the amount of air- molecules-per-second-per-square-meter the is blown into the room -- and visa versa. Hence, the subject in the room doesn't feel any sucking or blowing.
Cooling should should be purely-radiant as possible.
Yes, heat absorbed into the radiant cooling panels is carried off using convection -- but this is not what the subject inside the room feels. The direct cooling effect on anything/anyone inside the room is radiant.
The radiant cooling panel is on the ceiling of the room.
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I thought radiant heat worked cause it put out infared energy. I know of no such radiant cooling.
The three ways to move heat are conduction, convection, and radiation. You can do conductive cooling, of course. If the air is very still. But, since air is an insulator, it won't be very effective.
My sense is that the laws and principles of physics aren't going to cooperate with you, here.
--
Christopher A. Young
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Your first problem...

Which you don't have...
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Stormin Mormon wrote:

Yes, basically. There is no "cold", only heat or absence of it. But, your body is at some sort of equilibrium with the rest of your immediate environment. So, you are receiving thermal radiation from the walls, floor and ceiling. If you put a cold plate between you and that warm surface, that radiation is cut off, and you become a more effective thermal radiator, as you are farther out of equilibrium with your surrounds, you lose more heat in balance, as you are receiving less. Of course, you DON'T NEED to cool those plates to 77 K to get the cooling effect!
Jon
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On Sat, 12 Jul 2008 12:58:25 -0700 (PDT), "Green Xenon [Radium]"

Hope you have your raincoat ready.
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