Heat conduction? copper

[alpha2cen]

We know well heat conduction macroscopically.

Metal have a good property to conduct heat.

But we deeply don't know heat conduction mechanism microscopically.

How the heat flow form here to there?

Any good opinion?

[John Cuthber]

"But we deeply don't know heat conduction mechanism microscopically."

Is this the Royal We?

http://en.wikipedia.org/wiki/Phonon

http://en.wikipedia.org/wiki/Green-Kubo_relations

[alpha2cen]

"But we deeply don't know heat conduction mechanism microscopically."

Is this the Royal We?

http://en.wikipedia.org/wiki/Phonon

http://en.wikipedia....-Kubo_relations

 

Metal has many free electrons, but insulator has a few free electrons.

And metal has a good electron conductivity, but insulator has not one.

Those relations do not contain electron contributions for the heat conduction.

And then, does heat capacity have no rule in this mechanism?

[insane_alien]

heat capacity plays a role in how quickly steady state state heat conduction is achieved. a higher heat capacity will take longer to reach steady state heat conduction(all other things being equal).

 

but for steady state heat conduction it doesn't play any role because the conductor isn't changing temperature.

[alpha2cen]

Any heat conduction is needed the temperature gradient.

If temperature gradient is big, much heat is transfered.

In this forum we are focused on the atomic level heat conduction mechanism.

[lemur]

My lay reasoning process is that heat exists as kinetic energy (vibration) of atoms/molecules and/or as EM radiation. So either the conductor has to act like a photon conduit, in a fashion similar to fiber-optic cable OR it has to be able to transfer kinetic energy (vibration) of atoms/molecules very quickly between particles. Since good conductors seem to have the general trait of having a lot of (loose) electrons surrounding them, which seems to allow the electrons to conduct waves of electrical energy easily; I would guess it's the same "looseness" that allows the nuclei to vibrate more easily. What I don't get is why vibration of the inner core transfers through the particle-chain without transforming into an electrical current. Someone told me that this is because of the nature/size of the wave. I believe they said that waves of electricity are much smaller than waves of heat through the conductor. I would guess, then, that the reason the electric current can result in heat is because the waves get so strong that their energy extends their amplitude more than their frequency/length, and this causes the cores of the atoms to vibrate. Again, though, this is lay extrapolation from multiple sources.

[alpha2cen]

Let's think about this.

 

Thermocouple, copper- constantan

copper*****|-------------------------------------------------------------------------------------------------------------|

constantan |-------------------------------------------------------------------------------------------------------------|

************hot...........................................................................................................cold

Above picture, there are two wires made of copper or constantan .

Each end point are attached.

When we place one point hot place and the other one cold place, electric driving force such as electric voltage is generated.

Some of heat transfer ability is changed into electric potential difference.

How do we explain this phenomena - heat transfer and electric potential difference correlation?

Edited December 20, 2010 by alpha2cen

[John Cuthber]

I explain it as a heat engine using electrons as the working fluid. Much the same as a steam engine is a heat engine using water as the working fluid.

If I wanted to be more detailed I would talk about the contact potentials, how they vary with temperature and how there is no reason to expect the contact potentials of two different metals to vary in the same way as the temperature changes.

BTW, this has bugger all to do with the original question.

[alpha2cen]

I explain it as a heat engine using electrons as the working fluid.

 

The device is already developed for refrigerator. But efficiency is not so high than refrigerant using refrigerator. At the power station this technology is used for collecting waste heat.

Then, What is the free electrons contribution mechanism for conducting heat?