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G0TEZ > TECH 28.02.04 13:49l 36 Lines 1348 Bytes #999 (0) @ WW
BID : 860387G0TEZ
Read: DB0FHN GUEST OE7FMI
Subj: re: Visible Colours and Heat.
Path: DB0FHN<DB0FOR<DB0MRW<DB0RGB<OK0PPL<DB0RES<ON0AR<ZL2TZE<GB7YFS
Sent: 040228/0947Z @:GB7YFS.#26.GBR.EU #:40453 [Bourne] $:860387G0TEZ
From: G0TEZ@GB7YFS.#26.GBR.EU
To : TECH@WW
A great man. Not just me, said that a body radiates as much as it
receives. The man I'm thinking of is Kirchoff who made the very self
evident statement that as much current flows away from a point as flows
into it. You probably did it for the RAE.
His statement about heat transfer is just as obvious. Your Black car
absorbs and radiates all wavelengths fron UV to IR. While your white one
reflects most of it.
In the cool of the morning, the calorific value to use an old term, of
your black car is much higher than the white and, keeping to Kirchoff's
law it radiates it's heat at the rate it absorbed it at high noon. This
melts your snow. The white car will also melt the snow. especially if it
gets some help from the sun but not as fast as the black one.
I remember replying to this topic a while ago and mentioning that people
in very hot countries where dark, loose clothes.
When I was young, this was little old ladies in Southern france, wearing
loose black clothing and shawls. I believe that Greek and Spanish grannies
did the same. The idea being that the all black ensemble radiated heat
faster than anything else.
A sort of 'black body' radiation.
All the best - Ian, G0TEZ @ GB7YFS.#26.gbr.eu
Message timed: 21:44 GMT on 25 Feb 04
email: ian@g0tez.fsnet.co.uk
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