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Author Topic: Can something be hotter than the heater?  (Read 2620 times)

Offline Geezer

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Can something be hotter than the heater?
« on: 21/09/2011 22:57:23 »
When heating something, is it possible to make the thing that is being heated hotter than the thing that's heating it without doing anything other than transferring heat? (No compression, chemical changes, etc.)


 

Offline RD

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Can something be hotter than the heater?
« Reply #1 on: 22/09/2011 01:04:17 »
Not all the molecules are moving at the same speed ...

http://www.saskschools.ca/curr_content/chem30_05/1_energy/energy1_4.htm

So some of the heater molecules could be moving slower than some of the heated molecules.
 

Offline Bored chemist

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Can something be hotter than the heater?
« Reply #2 on: 22/09/2011 06:53:06 »
It's a matter of definition but you can get things very hot with laser heating.
 

Offline Geezer

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Can something be hotter than the heater?
« Reply #3 on: 22/09/2011 07:02:03 »
It's a matter of definition but you can get things very hot with laser heating.

Yes, that would work. A magnifying glass might work too.

I should probably qualify the question a bit. I was thinking of a situation where the heat is transferred primarily by conduction in some sort of heat exchanger.
 

Offline peppercorn

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Can something be hotter than the heater?
« Reply #4 on: 22/09/2011 11:42:23 »
I should probably qualify the question a bit. I was thinking of a situation where the heat is transferred primarily by conduction in some sort of heat exchanger.
This seems an odd question from someone of your, er, experience to be asking, Geezer.
...I'm guessing there must be something that makes you think that, what appears to be an unworkable situation, isn't necessarily so - could you share your thinking?


I actually had a similar thought some years ago when trying to think up a design for a solar-powered engine.
Ultimately though, any device I could conceive would still require a gas (air for simplicity) to be able to expand as it heated and then there is no way to avoid extra work being added if it's to be compressed (to allow higher T) again.
 

Offline lightarrow

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Can something be hotter than the heater?
« Reply #5 on: 22/09/2011 13:20:59 »
It's a matter of definition but you can get things very hot with laser heating.

Yes, that would work. A magnifying glass might work too.

I should probably qualify the question a bit. I was thinking of a situation where the heat is transferred primarily by conduction in some sort of heat exchanger.
But if you use laser, lenses, ecc, you are not using heat.
By definition, heat is the exchange of energy caused by a temperature difference only.
So, the heater *must* be hotter than the heated. Otherwise it's not heat...
 

Offline Geezer

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Can something be hotter than the heater?
« Reply #6 on: 22/09/2011 16:41:58 »

This seems an odd question from someone of your, er, experience to be asking, Geezer.
...I'm guessing there must be something that makes you think that, what appears to be an unworkable situation, isn't necessarily so - could you share your thinking?


I'm a amateur, particularly in matters Thermodynamic. I was playing around with a thermodynamic calculator and it allows the situation I'm referring to. At first I thought it was ridiculous, but I think it's legitimate.
 

Offline CZARCAR

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Can something be hotter than the heater?
« Reply #7 on: 22/09/2011 18:31:25 »
a cold brick is placed atop a hot brick in a perfectly insulated enclosure. Eventually, the 2 bricks the same temp & then?
a hot brick is placed atop a hot brick with same scenario, & then what?
Q= does conductive heat act like convective in that it rises vs gravity?
 

Offline CliffordK

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Can something be hotter than the heater?
« Reply #8 on: 22/09/2011 20:04:58 »
Heat is just a form of energy.

"Hotter than the Heater"?

What about a heat pump?  Start with a rarefied gas.  Heat it up.  Compress the gas, and your end product is hotter than the initial gas.

Focused light was mentioned above.  Cubic Zirconium is made with an interesting process, I believe with essentially focusing a beam of microwaves at the middle of the crucible which is made out of powdered cubic zirconium.  Anyway, since it must be quite hot, the middle of the powdered precursor is heated without heating the edges to a temperature hot enough to melt the container.
 

Offline Geezer

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Can something be hotter than the heater?
« Reply #9 on: 22/09/2011 20:14:33 »
Heat is just a form of energy.

"Hotter than the Heater"?

What about a heat pump?  Start with a rarefied gas.  Heat it up.  Compress the gas, and your end product is hotter than the initial gas.


Nope. No gas compression during the heat transfer.
 

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Can something be hotter than the heater?
« Reply #9 on: 22/09/2011 20:14:33 »

 

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