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Post by Andrew on Aug 29, 2013 10:12:37 GMT
Today in Helsinki the sky temperature was -9.6C measured in the North East at about 20 degrees from the verticle at 11am with a clear view to blue sky. Later at 12:50 it was -8C, and with a cling film cover over the radiation thermometer the temperature was -5.4C. The local air temperature was about 20C as measured by an ordinary thermometer.
Therefore it seems possible to build an enclosed insulated box that points towards the cold sky away from local warmer objects such as trees and buildings and cool the inside of the box to quite low temperatures which are significantly below the temperature of the near surface air.
Essentially the fridge will be a radiation thermometer.
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Post by numerouno on Aug 29, 2013 10:24:53 GMT
I'm sure you will be documenting everything carefully? The people in the developing countries will be delighted with the free ice, so I can see marketing prospects!
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Post by Andrew on Aug 29, 2013 11:12:00 GMT
I'm sure you will be documenting everything carefully? The people in the developing countries will be delighted with the free ice, so I can see marketing prospects! Ice via cooling to space would have been the preserve of rich people rather than hobbyists with time on their hands to test that what seems probable is factual. Anyway my tech will be very simple and science is not developed just by making well documented claims. Instead other people build the things and use them. The hard part at the moment is unblocking my foam gun! :-)
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Post by numerouno on Aug 29, 2013 11:48:02 GMT
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Post by Andrew on Aug 29, 2013 12:24:36 GMT
I have an arrangement ready and set up. Very difficult to position it at ground level without it being in sight of local objects - likely have to go on the roof. It is now about 20.7C in the protected shade here, and there is quite alot of high cloud and the sky temperature is higher than -3C and it is going to take ages for the thermal mass of the insulation to be overcome. Even so some sort of reduction in the shade temperature should be possible. The gadget is currently reading 24.7 but i built it in a sunny location. It was 28.6 when i put it in position Edit: I have put it on the roof where it is being heated by the sun. So it will have to be for night time testing only.
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Post by numerouno on Aug 29, 2013 12:52:18 GMT
But you have put the aluminium foil within the insulation somewhere, have you not?
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Post by Andrew on Aug 29, 2013 13:38:37 GMT
But you have put the aluminium foil within the insulation somewhere, have you not? Yes. I made a box and lined it will foil and put a cling film window on it. I have moved the device to the roof where it will have to wait for night time readings as it is now being heated by the sun. Unfortunately on the roof it still has line of sight to very tall trees.
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Post by numerouno on Aug 29, 2013 13:59:24 GMT
"Yes. I made a box and lined it will foil and put a cling film window on it. "
Fine, but no cheating with cling film as that was not the Indian way for sure, and you have not checked its radiation properties.
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Post by Andrew on Aug 29, 2013 14:15:08 GMT
"Yes. I made a box and lined it will foil and put a cling film window on it. " Fine, but no cheating with cling film as that was not the Indian way for sure, and you have not checked its radiation properties. ? The idea is simply to demonstrate that cooler temperatures can be achieved at the surface than the air temperature thru which the radiation has to pass. The cling film is only to make the test possible in windy conditions - assuming that idea works Clingfilm is semi transparant to radiation. Quite possibly it will work better without it as the sky temperature is significantly warmer when measured thru cling film. I dont think we need to control for magical properties coming from cling film at this stage.
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Post by numerouno on Aug 29, 2013 14:56:44 GMT
Andrew, I don't know if you have noticed the fact that the cling film will very effectively limit any heat loss by evaporation, so the circumstances will not be authentic and/or comparable.
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Post by Andrew on Aug 29, 2013 15:09:21 GMT
Andrew, I don't know if you have noticed the fact that the cling film will very effectively limit any heat loss by evaporation, so the circumstances will not be authentic and/or comparable. There is no water in my device. Anyway evaporation cools water. Supposedly you can get 10F under the local air temperature with this kind of device at night in dry clear sky conditions. The idea has been fairly extensively tested for a passive night time cooling system using the radiating surface of a metal roof and using low power fans to circulate the warm air inside the house against the inside of the metal roof It is an ancient idea and is far from being rocket science. The green house effect depends on it being factual. The hardest part of observing the effect is the dry clear sky conditions and the absence of wind to warm the radiating surface and an absence of local objects that are in the line of sight of the plate that radiates to space/the very cold upper atmosphere.
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Post by numerouno on Aug 29, 2013 15:57:28 GMT
Oh, but I thought the whole objective was to reproduce the ice-making of the ancient Indians, as this I think you started from and told us would presumably work? But of course they would not have had the shining foils either.
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Post by Andrew on Aug 29, 2013 17:04:23 GMT
Oh, but I thought the whole objective was to reproduce the ice-making of the ancient Indians, as this I think you started from and told us would presumably work? But of course they would not have had the shining foils either. I need dry clear windless nights for best capability to make ice John Tyndall got travellers to collect temperature and humidity data and observed that it gets very dry in parts of Asia, Australia and Africa so that it is possible to observe extreme night and day temperature differences. I am more or less surrounded by water here, so I doubt I can produce ice on an Autumn night like the Indians apparently could. I have had 13.1C here so far at sunset with an air temperature of about 17C, but it is very difficult to measure air temperature accurately and I have no method for that at all. The Sky temperature is not very low now so 13.1C is not bad 20:23 12.2C -------------20:30 Sky temperature -5.8C diffuse high cloud 21:00 9.3C air 15.1 sky -9.8 Probably quite humid as sky has grey tint. Dusk. 21:32 9.5 air 14.5 sky -3.0 some high cloud. Saw 8.4 before the sky warmed 06:00 8.0 air 12.2 sky +3.0 overcast
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Post by icefisher on Aug 29, 2013 17:32:59 GMT
Anyway my tech will be very simple and science is not developed just by making well documented claims. :-) My thats an interesting statement. Is this going to be the proof of greenhouse warmingcooling?
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Post by nonentropic on Aug 29, 2013 18:55:26 GMT
I don't think there is any such thing as sky temperature. realizing that as I write this there may well be a translation imperfection.
but regardless the point of this is that the mixing up of radiation with conduction is the issue. technically space has a temperature defined by the molecular velocity and mass of the very sparsely separated atmosphere out there. a thermometer will tell you nothing.
I have solar panels that regularly show a low thermocouple temperature inside the units (there are several in the system)on a cloudless night after some hours of exposure to a dark clear sky relative to the surrounding environmental air.
the conditions for such a 'Sky Fridge' to exist limits it real-world application, but the sky needs to be very dry and cloudless the solar units are well insulated from beneath the glass panel is sealed and is able to insulate from the top and it needs to be able to reradiate a significant portion of the IR from the surface of the copper panels.
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