Radiation is heat transfer by the emission of electromagnetic waves
which carry energy away from the emitting object. For ordinary
temperatures (less than red hot"), the radiation is in the infrared
region of the electromagnetic spectrum.
The Electromagnetic Spectrum
Radiation heat transfer is concerned with the exchange of thermal
radiation energy between two or more bodies.
"Thermal radiation is defined as electromagnetic radiation in the
wavelength range of 0.1 to 100 microns (which encompasses the visible
light regime), and arises as a result of a temperature difference
between 2 bodies. "
Thermal radiation encompasses more than visible light region. See
"The radiant heat you feel from an oven or a fire is infrared
"Thermal radiation is electromagnetic radiation emitted from the
surface of an object which is due to the object's temperature.
Infrared radiation from a common household radiator or electric heater
is an example of thermal radiation, as is the light emitted by a
glowing incandescent light bulb. Thermal radiation is generated when
heat from the movement of charged particles within atoms is converted
to electromagnetic radiation."
"Infrared (IR) radiation is electromagnetic radiation of a wavelength
longer than that of visible light, but shorter than that of radio
As for whether *heat* (in the form of thermal radiation) goes down or
goes up would depend on a lot of factors. http://www.elmhurst.edu /
Although there is such a thing as thermal radiation and radiation heat
transfer, there is still the fact that the energy goes through a couple of
conversions in the process. Heat is converted to electromagnetic
radiation, and electromagnetic radiation is converted back to heat when it
is absorbed. "Radiant heat" is still electromagnetic radiation.
- Don Klistein ( firstname.lastname@example.org)
Thermal radiation is mostly found in that range, but it does exist
outside that range. If the temperature is outside the range of roughly 30
to 30,000 Kelvin, then the peak of the spectral power distribution of the
thermal radiation will be outside the .1-100 micron range.
- Don Klipstein ( email@example.com)
On 6 Feb 2007 05:53:37 -0500, firstname.lastname@example.org wrote:
There is, of course, no such thing as "infra-red heat rays".
Infra-red is electromagnetic radiation (in a frequency range just
below the low end of the visible spectrum). Heat is the
mechanical vibration of molecules, something quite different.
You misunderstand the nature of the air movement it blocks. Insulation in a
wall cavity is not there to stop the transport of air through the cavity in
the wall; it's there to prevent convective circulation of air *within* the
cavity, which is a *highly* efficient means of transporting heat from the
interior wall to the exterior wall.
Hope you never have a fire. Styrofoam burns like there's no tomorrow, and
emits toxic gases while it does.
Doug Miller (alphageek at milmac dot com)
On Feb 6, 7:48 am, email@example.com (Doug Miller) wrote:
Seems what JSM has discovered is that one way heat can be transfered
is via radiation and is now dismissing the two other methods,
conduction and convection. It's the latter which is associated with
"heat rises", but which should be more appropriately referred to as
hot air rises.
Heat spontaneously/rapidly dissipates ( from hot to cold ) through metal.
Photons and circulating air, including isolated pockets of air, also do it.
Workers at my little grocery store measure the temperature of things
using a " gun " that measures the peak frequency of
" black body " ( i.e. a gaussian " bell " curve ) radiation.
The higher the peak frequency, the hotter the object.
The gas inside some galaxies ( at the center of galaxy clusters )
is so hot it emits x-rays ( and electrons run free, as a plasma ).
The tiles on the space shuttle ( there to prevent burnup on reentry )
are made of aerated silicon... Forgive me if I take their word over yours.
There are other measures of " coldness ",
e.g. the particles in a gamma ( or atom ) laser are at absolute zero
if they're perfectly coherent... as modeled by Bose-Einstein statistics.
Heat energy can be transferred from one area to another by three
methods: conduction, convection, and radiation.
a) Conduction is when the two materials are directly touching each
other. Heat flows from the warmer into the cooler.
b) Convection is when air is circulating between two materials,
absorbing heat energy from the warmer and tranferring it to the cooler.
c) Radiation is the photons given off by the material.
Proper insulation requires protecting against all three types of heat
transfer. Any reflective surface will guard against radiation, but a
layer of aluminum foil does nothing to protect against conduction or
convection. Yes, styrofoam is more efficient at guarding against
convection than fiberglass. It's also a lot more expensive for a given
R value, it's highly flammable, and when it burns it gives off toxic fumes.
You confuse the concepts of heat and hot air. While your post is a good example
of hot air, it differs from the hot air in a house. Hot air does rise. But
heat moves by radiation, convection and conduction. I would hazard a simple
guess that the bedroom is not any warmer because it is not getting much heat in
the first place. [Take something very cold and insulate it - will it get warm?
NO!] Besides, the nights probably got colder while you were doing your
Francis A. Miniter
So solly! But honored gentleman would seem to have brundered into
wong house! Perhaps he would do well to first attend to the matter of
just who in his erring judgment he would suppose himself to be
addressing after such ill-tempered, and disrespectful, fashion?
Confucius say, "Confusion is often to be found in the peanut butter
smear on some poor man's honorable spectacles!"
It is precisely the confusion of heat with hot air in the mind of
others which is the subject under consideration, here.
"A book is a mirror, if an ass peers into it, you can't expect an
apostle to peer out." - Georg Lichtenberg
"Who Did the Dahlia?"
"Then?" I drained the last of my coffee.
"Yes! What else can you dig up to convince me that the sleazy little
harlot got just what she deserved?"
I set down my cup, and was pleased to see that she was hailing the
waiter with her empty Martini glass: it looked like my ruse was
working. "You sure you want another? That is your third, darling."
"Darn tootin!" She lightly banged her pretty little fist on the table.
"Because ya know why?"
"Cuz now you've got me committed to the vindication of this woman, and
I'm gonna see it through."
I sat back. "No more giving the dough back to Maurice?"
"No way. I'm not scared, see? Why, just have a look at me. I'm a
private eye, aren't I?"
"One for the lovely lady Sam Spade!" said the waiter, having taken the
empty, to set down the full. "And one more for the gent." He
I looked at him. "Well? What you want--a hot tip on the horses?" He
turned on his heel and was gone.
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