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Re: Dew Formation

At 01:04 PM 3/13/2004, John M., you wrote:
>When dew forms on clear nights, it will heavily wet lawns but will
>hardly ever leave visible moisture on concrete walkways or asphalt
>roads. There are many factors that regulate condensation:
>temperature, available condensation nucleii, curvature, hydrophilic
>surfaces, etc. - but I am having difficulty identifying the primary
>one in this case. Any ideas out there?

The primary mechanism is radiation exchange with 2 pi steradians of a
3 kelvin blackbody plus high resistance thermal conduction pathways
to the ground and the (still) air.

John Mallinckrodt

If we are to believe John, a vacuum enclosure with a suitably
transparent lid would allow a black chromed copper square (say),
if well insulated at sea-level, to cool to 5 or 6 K overnight?
I don't think so.
I think you would find it rather difficult to radiatively
chill any object at sea level to below -100 degC

Perhaps someone would care to try it?

Brian Whatcott Altus OK Eureka!