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Author Topic: Does A Vacuum Affect Temperature ?  (Read 13484 times)

Offline neilep

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Does A Vacuum Affect Temperature ?
« on: 28/03/2008 00:19:42 »
Dearest Vacuumologists,

There's been a recent windfall of vacuum orientated questions recently and I felt the need to add my own ?


See this Vacuum chamber ?



Nice eh ?...Now that's a quality piece of air extraction kit !!

Tempereature relies on molecules banging away at each other yes ?....so...if I place a hot piece of metal in the chamber...suck out all the air....will I be able to feel the heat ?....or....perhaps I should ask...will I be able to feel the heat as efficiently as if there was air still there ?


How does a vacuum affect temperature of stuff ?


whajafink ?

*le thank ewe*








 

Offline turnipsock

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Does A Vacuum Affect Temperature ?
« Reply #1 on: 28/03/2008 00:58:48 »
I think not.
 

another_someone

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Does A Vacuum Affect Temperature ?
« Reply #2 on: 28/03/2008 00:59:26 »
Heat is the transfer of energy, and the simplest way is through kinetic energy, with atoms/molecules bumping into each other, but it is not the only way.

If you have a hot piece of metal sitting in the vacuum, it will be radiation infra red radiation, and you can feel that heat, but it will only be a small proportion of the energy you would feel if you could touch the hot metal.
 

Offline turnipsock

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Does A Vacuum Affect Temperature ?
« Reply #3 on: 28/03/2008 01:32:39 »
What would happen if you had one of these cameras that show my groin as red, you know the ones that show heat. Would that still respond to a bit of hot metal inside a vacuum chamber?

The shape of that vacuum chamber gives me an idea.
 

Offline Supercryptid

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Does A Vacuum Affect Temperature ?
« Reply #4 on: 28/03/2008 01:45:43 »
The hot piece of metal would remain hot for a much longer period of time in a vacuum chamber than in room-temperature air. In air, the hot metal can relinquish its heat through conduction (that is, the metal can transfer its heat to the air that surrounds it). It can also release heat as radiation such as IR as was already said before me.

In a vacuum, only radiation can cause the temperature to drop in the metal. So no, you wouldn't feel it as efficiently in a vacuum chamber as you would in air if you tried to feel the heat at a distance. If you were in the vacuum chamber with the metal, and touched it, it would still feel as hot as if you touched it in air. This is because the heat is being directly conducted by your hand in both cases.
 

Offline Soul Surfer

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Does A Vacuum Affect Temperature ?
« Reply #5 on: 28/03/2008 11:15:14 »
You "feel" heat by the infra red radiation emitted from hot objects.  The infra red radiation absorbed by the air is pretty small so if you placed your red hot iron bar in the vacuum chamber with air in it and covered it with the belljar and felt the heat radiating from it through the air and the glass and then evacuated it to create a vacuum you would not notice the difference however as there is no air to absorb any infra red radiation you would get a slight increase in the radiation you are receiving.
 

lyner

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Does A Vacuum Affect Temperature ?
« Reply #6 on: 30/03/2008 12:14:50 »
Quote
Temperature relies on molecules banging away at each other yes ?
This is an old chestnut; the difference between heat and temperature.
Temperature IS actually the average Kinetic Energy of the molecules (or, in the case of a metal, the electrons, too). The few molecules of air in your vacuum chamber may have the same average KE as if the jar were full of air; both can be at the same temperature. However, the AMOUNT of energy is greater in the full jar because there are more molecules. Nowadays we refer to Heat as Internal Energy.
Your nerves 'detect' temperature changes on your skin surface. You can change the temperature by transferring heat by any of the known heat transfer processes - conduction(touch a hot/cold brick), convection (blow hot/cold air), radiation (under the grill) or evaporation (blow on a wet hand). There is also RF heating.

BTW, anyone who has a red groin must need some suitable cream applied to it!
« Last Edit: 30/03/2008 12:17:15 by sophiecentaur »
 

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Does A Vacuum Affect Temperature ?
« Reply #6 on: 30/03/2008 12:14:50 »

 

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