2006-09-09 04:47:22 · 7 answers · asked by Ejsenstejn 2 in Science & Mathematics ➔ Physics
i was taught that the surface that absorbed most also radiated most. I qoute from Wikipedia
"In practice no material has been found to absorb all incoming radiation, but carbon in its graphite form absorbs all but about 3%. It is also a perfect emitter of radiation"
The question is about emission of internally generated heat. Convection and conduction play the role of getting the heat to the surface but emission of energy is a surface phenomenon.
Painting a surface black should therefore improve its emission property since black absorbs most compared to other surfaces. .
2006-09-09 06:02:16 · answer #1 · answered by rabi k 2 · 0⤊ 0⤋
Yes. Emissivity (between 0 and 1) measures how close a surface comes to emitting radiant heat at the maximum possible rate, which is that of a perfectly black body. Emissivity is, for thermodynamic reasons, the same as its absorption efficiency, and an (ideal) black body absorbs all incoming light (ie reflects none). A surface with emissivity of 0, for example, reflects all light, making it white, while a surface with emissivity of 1 is perfectly black.
2006-09-09 13:37:13 · answer #2 · answered by Dr. R 7 · 0⤊ 0⤋
Black surface paint does not facilitate the emission of internally generated heat as it is absorbs energy from the sun in the form of rays.
Note; All it depends upon the chemical structure of dyestuff used for dyeind of the goods.
2006-09-09 12:35:42 · answer #3 · answered by niceboy302 1 · 0⤊ 1⤋
Heat is radiated in the thermal infrared region at wavelengths larger than 2 micrometer.
The color of the surface at these wavelengths determines the emission coefficient. This color is not necessarily related to the color in the visible wavelength region (0.4-0.8 micrometer).
It turns out that both black and white painted surfaces are almost black in the thermal infrared region and have a high thermal emission.
Metal surfaces like copper or chromium have a very low thermal emission.
2006-09-09 12:10:06 · answer #4 · answered by mitch_online_nl 3 · 0⤊ 0⤋
No, unless the surface is rougher after painting than before. The emission depend on area and the thermal conductivity of the 2 mediums.
The black paint will help the absorbtion of energy, not emision, only if that energy comes as radiant energy (like electromagnetic energy from the sun) but it won't affect the transfer thru convection (contact).
2006-09-09 12:06:28 · answer #5 · answered by Zeke 2 · 0⤊ 1⤋
No, black surfaces are also good reflectors of heat.
2006-09-09 12:00:15 · answer #6 · answered by ag_iitkgp 7 · 0⤊ 1⤋
yes. internal colour isn't black.
2006-09-09 11:52:22 · answer #7 · answered by DarlaTremere 2 · 0⤊ 1⤋