| Topic: |
Science > Physics |
| User: |
"MBS" |
| Date: |
11 Dec 2003 09:42:26 PM |
| Object: |
Solar heat reflection? |
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
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| User: "Paul R. Mays" |
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| Title: Re: Solar heat reflection? |
11 Dec 2003 10:14:29 PM |
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"MBS" <mbstruss@bellsouth.net> wrote in message
news:bd9a8bf2.0312111942.1d00924b@posting.google.com...
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
I'm sure someone will correct me if I'm incorrect but
mirrored is what you would want...
Reasoning...
The full spectrum of light of the sun does not make it
to the surface due to filtering of the different layers..
In the case of direct IR wave lengths from the sun most
are reflected by the same greenhouse gases that keep
the IR produced by objects heated by all the remaining
spectra that passes the atmospheric filters. The IR wave
lengths that heat our ball are produced by "stuff" that
absorbs material specific wave lengths ( material
specific wave lengths just means that some stuff absorbs
some wave lengths and reflect others.. If it absorbs
it converts the inertial energy of the wave and you
get thermal conversion which is noted as a IR Wave ...
Which is a variable spread of frequencies that we
can wave form measure and detect as a "heat" source
to our skin...
So.. You get little IR wave lengths making through
the atmosphere and due to the Ozone you get little
UF end of spectrum... So to get coolest coat a mirrored
coat would reflect most energetic wave lengths that
would be converted to IR .... If you step out side our
balls protective gas.... You would want to add UV
and IR wave length reflective coatings also...To you it
would still look mirrored... But I think it would be gold
mirror color.....
IMHO.... But sounds good to me....
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| User: "Mark Folsom" |
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| Title: Re: Solar heat reflection? |
11 Dec 2003 11:19:43 PM |
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"Paul R. Mays" <uce@ftc.gov> wrote in message
news:XqWdnZ2sWaU-3USi4p2dnA@giganews.com...
"MBS" <mbstruss@bellsouth.net> wrote in message
news:bd9a8bf2.0312111942.1d00924b@posting.google.com...
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
I'm sure someone will correct me if I'm incorrect but
mirrored is what you would want...
Reasoning...
The full spectrum of light of the sun does not make it
to the surface due to filtering of the different layers..
In the case of direct IR wave lengths from the sun most
are reflected by the same greenhouse gases that keep
the IR produced by objects heated by all the remaining
spectra that passes the atmospheric filters. The IR wave
lengths that heat our ball are produced by "stuff" that
absorbs material specific wave lengths ( material
specific wave lengths just means that some stuff absorbs
some wave lengths and reflect others.. If it absorbs
it converts the inertial energy of the wave and you
get thermal conversion which is noted as a IR Wave ...
Which is a variable spread of frequencies that we
can wave form measure and detect as a "heat" source
to our skin...
So.. You get little IR wave lengths making through
the atmosphere and due to the Ozone you get little
UF end of spectrum...
http://www.inframet.pl/Education/Fundamentals/Transmission.pdf
I think you overestimate the absorption and reflection of infrared by the
atmosphere. The above website has some informative plots of same.
Greenhouse gases mostly absorb, rather than reflect infrared.
A mirrored surface is better than a diffuse reflective surface, because a
diffuse reflector allows for multiple absorption opportunities. Silver is
probably a slightly better reflector than gold, but it tarnishes and needs
to be protected by a transparent coating.
Mark Folsom
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| User: "Franz Heymann" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 05:32:46 AM |
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"MBS" <mbstruss@bellsouth.net> wrote in message
news:bd9a8bf2.0312111942.1d00924b@posting.google.com...
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
You would need to look up data on reflectivity versus wavelength if you
wanted a quantitative answer.
Qualitatively, an aluminised mirror is an excellent reflector of solar heat.
Experiments were done in India in which polished concave aluminium surfaces
were used as al fresco heat sources for cooking. Many people wounded their
hands seriously during the course of the tests.
To return to your last question:
Paint the surface facing the sun white and the opposite surface black.
Franz Heymann
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| User: "Sam Wormley" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 12:36:31 AM |
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MBS wrote:
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
Dielectric Coatings
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| User: "Mark Folsom" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 10:54:20 AM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FD961E5.A5DA278D@mchsi.com...
MBS wrote:
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
Dielectric Coatings
Dielectric coatings *could* make it absorb more.
Mark Folsom
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| User: "Sam Wormley" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 12:08:53 PM |
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Mark Folsom wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FD961E5.A5DA278D@mchsi.com...
MBS wrote:
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
Dielectric Coatings
Dielectric coatings *could* make it absorb more.
Mark Folsom
However dielectric coatings are generally tailored to work
at specific wavelengths and angles to provide maximum reflectance.
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| User: "Franz Heymann" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 02:44:44 PM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FDA0431.B1D527C8@mchsi.com...
Mark Folsom wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FD961E5.A5DA278D@mchsi.com...
MBS wrote:
I am curious about which surfaces or coatings on a metal would
reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
Dielectric Coatings
Dielectric coatings *could* make it absorb more.
Mark Folsom
However dielectric coatings are generally tailored to work
at specific wavelengths and angles to provide maximum reflectance.
Think of bloomed lenses.
Franz Heymann
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| User: "Mark Folsom" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 06:18:32 PM |
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"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FDA0431.B1D527C8@mchsi.com...
Mark Folsom wrote:
"Sam Wormley" <swormley1@mchsi.com> wrote in message
news:3FD961E5.A5DA278D@mchsi.com...
MBS wrote:
I am curious about which surfaces or coatings on a metal would
reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
Dielectric Coatings
Dielectric coatings *could* make it absorb more.
Mark Folsom
However dielectric coatings are generally tailored to work
at specific wavelengths and angles to provide maximum reflectance.
Unless they're antireflection coatings.
Mark Folsom
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| User: "John Popelish" |
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| Title: Re: Solar heat reflection? |
11 Dec 2003 11:34:01 PM |
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MBS wrote:
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
There are white coatings that reflect almost all incident light (and
infrared), and a mirror polish also reflests most light. The main
difference is that the mirror reflects spectrally (incident angle
equals reflected angle) while white reflects in all directions
(diffuse reflection). But the absorbed light can be very small (1% or
so) in either case. So either can keep the reflector cool, but if you
want to concentrate the reflected light someplace else in particular,
the mirror is way better.
--
John Popelish
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| User: "Mark Folsom" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 10:53:29 AM |
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"John Popelish" <jpopelish@rica.net> wrote in message
news:3FD9537F.FE234B2C@rica.net...
MBS wrote:
I am curious about which surfaces or coatings on a metal would reflect
the most solar heat. I know that a mirrored surface would relect the
most visible light but what about heat? I.e., would the underside of
the metal be the coolest if it had a mirrored surface or a glossy
white surface facing the sunlight?
Thanks!
There are white coatings that reflect almost all incident light (and
infrared), and a mirror polish also reflests most light. The main
difference is that the mirror reflects spectrally
that would be "specularly"
(incident angle
equals reflected angle) while white reflects in all directions
(diffuse reflection). But the absorbed light can be very small (1% or
so) in either case. So either can keep the reflector cool, but if you
want to concentrate the reflected light someplace else in particular,
the mirror is way better.
--
John Popelish
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| User: "John Popelish" |
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| Title: Re: Solar heat reflection? |
12 Dec 2003 06:49:28 PM |
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Mark Folsom wrote:
There are white coatings that reflect almost all incident light (and
infrared), and a mirror polish also reflests most light. The main
difference is that the mirror reflects spectrally
that would be "specularly"
Thank you. grumble...spell checker...
--
John Popelish
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