Post by Andrew on Mar 27, 2012 8:41:57 GMT
The clear sky temperature far above the surface can be surprisingly cold. Providing there is no wind and the air is very dry you can regularly create ice at night, when the ground air temperature is 45F or 7.2C
The solar oven is just a parabolic reflector to focus the suns rays, but you can do the same thing with just some foil placed crudely in a bucket.
All the warmth that is inside the foil has no heat source, other than the warm conducting and slightly radiating dry air. The dry radiating air extends far above the foil but radiates so little energy the bag can still cool thru the warmer air.
If the inside of the bucket made of foil, is undisturbed by air currents, the air is cooled inside the foil bucket and ice forms even though the foil is being heated by the warm air outside the bucket.
Related to this, in the driest hottest parts of the world, the night time temperature can be amazingly lower than the already reasonably high day time temperature.
books.google.fi/books?id=HZEAAAAAMAAJ&pg=PA417&dq=tyndall+heat+as+a+mode+of+motion+iron+grip&hl=en&sa=X&ei=n3lxT-uMGKqp4gTw2f2XDw&redir_esc=y#v=onepage&q&f=false
John Tyndall wrote in 1869 that Mitchell reported [at 1300 feet in Southern Queensland Australia] on 2nd of June 1846, -11.6C was recorded at sunrise, and 19.6C at 4pm, on the 12th the range was 29C but on many other days in June the range was almost 29C.
Dr Livingstone in June also recorded large temperature differences of 48F when away from the Zambesi river, but only 12F once once over the hills where the Zambesi river began.
These large temperature ranges were all entirely attributed to the absence of a concentrated radiating 'blanket' of water vapour. Water is however always present in even the driest air on earth in Antarctica.
The solar oven is just a parabolic reflector to focus the suns rays, but you can do the same thing with just some foil placed crudely in a bucket.
All the warmth that is inside the foil has no heat source, other than the warm conducting and slightly radiating dry air. The dry radiating air extends far above the foil but radiates so little energy the bag can still cool thru the warmer air.
If the inside of the bucket made of foil, is undisturbed by air currents, the air is cooled inside the foil bucket and ice forms even though the foil is being heated by the warm air outside the bucket.
Related to this, in the driest hottest parts of the world, the night time temperature can be amazingly lower than the already reasonably high day time temperature.
books.google.fi/books?id=HZEAAAAAMAAJ&pg=PA417&dq=tyndall+heat+as+a+mode+of+motion+iron+grip&hl=en&sa=X&ei=n3lxT-uMGKqp4gTw2f2XDw&redir_esc=y#v=onepage&q&f=false
John Tyndall wrote in 1869 that Mitchell reported [at 1300 feet in Southern Queensland Australia] on 2nd of June 1846, -11.6C was recorded at sunrise, and 19.6C at 4pm, on the 12th the range was 29C but on many other days in June the range was almost 29C.
Dr Livingstone in June also recorded large temperature differences of 48F when away from the Zambesi river, but only 12F once once over the hills where the Zambesi river began.
These large temperature ranges were all entirely attributed to the absence of a concentrated radiating 'blanket' of water vapour. Water is however always present in even the driest air on earth in Antarctica.