Myth: Heat Rises

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And it still isn't, regardless of how many times that myth gets posted!

and nonsense.
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Wrong :-)
Nick
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On 6 Feb 2007 16:07:48 -0500, snipped-for-privacy@ece.villanova.edu wrote:

There's a "problem" with reality. It often won't do as it's told. Heat and IR continue to be completely different things.
--
Mark Lloyd
http://notstupid.laughingsquid.com
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Wrong again :-)
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

Care to elaborate?
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Mark Lloyd wrote:

Hot (and even cold) bodies emit infrared, so they're often confused.
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Same here.

Heat Radiation http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html 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 http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html#c1 ------------------------------------------------------- Radiation heat transfer is concerned with the exchange of thermal radiation energy between two or more bodies.
http://www.efunda.com/formulae/heat_transfer/radiation/overview_rad.cfm says
"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 below
http://www.weatherquestions.com/What_is_infrared_radiation.htm "The radiant heat you feel from an oven or a fire is infrared radiation"
http://en.wikipedia.org/wiki/Thermal_radiation "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 radiation: http://en.wikipedia.org/wiki/Infrared_radiation
"Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. "
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 / ~chm/vchembook/globalwarmA5.html

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Amanda wrote:

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 ( snipped-for-privacy@misty.com)

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 ( snipped-for-privacy@misty.com)
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Wrong.
Nick
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On 6 Feb 2007 05:53:37 -0500, snipped-for-privacy@ece.villanova.edu 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.
--
Mark Lloyd
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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.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Feb 6, 7:48 am, snipped-for-privacy@milmac.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.
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Hi J_Seymour_MacNicely, 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.
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How did your workers get the gun to the galaxies and the space shuttle?
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J Seymour MacNicely wrote:

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.
Chris
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Yes, styrofoam is more efficient at guarding against

which can cause daine bramage :)
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J Seymour MacNicely wrote:

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 "testing".
Francis A. Miniter
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wrote:

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
-- Mackie http://vignettes-mackie.blogspot.com / "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?"
"No idea."
"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 straightened up.
I looked at him. "Well? What you want--a hot tip on the horses?" He turned on his heel and was gone. -- http://vignettes-mackie.blogspot.com /
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Hot air does NOT rise. Cool air FALLS displacing warmer air forcing it upwards. PHYSICS.
--
JET_FEATHER

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Tell me -- does ice float? Or does water sink?
--
Regards,
Doug Miller (alphageek at milmac dot com)
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