Notices
Results 1 to 18 of 18
Like Tree4Likes
  • 1 Post By Harold14370
  • 1 Post By Strange
  • 1 Post By Strange
  • 1 Post By JonG

Thread: How do you make a heat condenser or condense heat ...........is there any way to keep electrons in an enclosed space

  1. #1 How do you make a heat condenser or condense heat ...........is there any way to keep electrons in an enclosed space 
    New Member
    Join Date
    Oct 2013
    Posts
    2
    How do you make a heat condenser or condense heat ...........is there any way to keep electrons in an enclosed space?
    Is there any way to condense heat


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Cosmic Wizard
    Join Date
    Aug 2013
    Location
    San Diego
    Posts
    2,227
    >How do you make a heat condenser or condense heat

    Condensers are heat exchangers. They radiate or conduct heat into the environment; this allows a gas to condense to a liquid. An example is a car's radiator or an air conditioning condenser.

    >is there any way to keep electrons in an enclosed space?

    What? What does that have to do with the first question? But yes its easy to keep electrons in an enclosed space. All matter does that. The negative plate of a capacitor keeps more electrons in an enclosed space.

    >is there any way to condense heat

    You seem to feel there is some similarities between "condensing heat" and "keeping electrons." What do you think the connection is?


    Reply With Quote  
     

  4. #3  
    New Member
    Join Date
    Oct 2013
    Posts
    2
    i thought the more electrons that are there the more energy that can be transferred
    Reply With Quote  
     

  5. #4  
    Forum Cosmic Wizard
    Join Date
    Aug 2013
    Location
    San Diego
    Posts
    2,227
    Quote Originally Posted by thethinkingdummy View Post
    i thought the more electrons that are there the more energy that can be transferred
    Electrons can be used as charge carriers to transport electrical charge. A given number of charge carriers moving from place to place in a given time is called "current" which is one measure of electrical power.

    That doesn't have much to do with "heat condensers."
    Reply With Quote  
     

  6. #5  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by thethinkingdummy View Post
    i thought the more electrons that are there the more energy that can be transferred
    It's true that more molecules will enable faster transfer of energy in the form of heat, via conduction or convection, as both of these processes depend on transferring heat by collisions between molecules. But this is about molecules, not electrons on their own.

    Electrons bound in atoms and molecules are responsible for some forms of radiation (mostly in the visible, UV and X-Ray regions) - which also transfer energy. But again, these are not free electrons.

    Other forms of energy transfer involve bulk behaviour of materials to do mechanical work, such as expansion of gases under pressure, falling weights, accelerating and decelerating objects, and so on. Electrons are not involved in these - except insofar as almost all matter is partly made of electrons.
    Reply With Quote  
     

  7. #6  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    So, electrical conductivity is related to the presence of conduction bands, and therefore "free" electrons, in metals. There appears to be some rough correlation between thermal conductivity and electrical conductivity ... I don't know the physics behind that ... but I wonder if that is what the OP is thinking of. (Although it doesn't sound like it )
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  8. #7  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by Strange View Post
    So, electrical conductivity is related to the presence of conduction bands, and therefore "free" electrons, in metals. There appears to be some rough correlation between thermal conductivity and electrical conductivity ... I don't know the physics behind that ... but I wonder if that is what the OP is thinking of. (Although it doesn't sound like it )
    Could be. Re the physics behind it, I imagine the difference is that heat will be transferred mainly via changes to the amplitude of vibration of the atomic cores, as these have almost all the mass and hence the KE involved in heat energy transfer. I seem to recall things called phonons, which are lattice vibrations. Perhaps there is also a continuum of possible vibrational states of the lattice, which would allow very easy excitation of successive modes of vibration and hence heat dissipation. Or something.

    But you're right we need a real physicist here, rather than a chemist speculatively speaking ex ano.
    Reply With Quote  
     

  9. #8  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,795
    Thermal conductivity - Wikipedia, the free encyclopedia
    In metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law, as freely moving valence electronstransfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. Highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator, but due to its orderly array of atoms it is conductive of heat via phonons.
    http://en.wikipedia.org/wiki/Wiedemann-Franz_law
    Strange likes this.
    Reply With Quote  
     

  10. #9  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by Harold14370 View Post
    Thermal conductivity - Wikipedia, the free encyclopedia
    In metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann-Franz law, as freely moving valence electronstransfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. Highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator, but due to its orderly array of atoms it is conductive of heat via phonons.

    Wiedemann
    And behold! A real physicist popped out of the woodwork...and all was light. Thanks very much. So phonons are important in insulators but electrons can conduct heat in metals.
    Reply With Quote  
     

  11. #10  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by exchemist View Post
    And behold! A real physicist popped out of the woodwork...
    Or he thought to look it up.
    Harold14370 likes this.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  12. #11  
    Forum Isotope
    Join Date
    Feb 2012
    Location
    Western US
    Posts
    2,857
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by exchemist View Post
    And behold! A real physicist popped out of the woodwork...
    Or he thought to look it up.
    And thus pass the Turing test for physicist-equivalency.
    Reply With Quote  
     

  13. #12  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,795
    Who needs a real physicist when you have Wikipedia?
    Reply With Quote  
     

  14. #13  
    Forum Junior
    Join Date
    Sep 2011
    Location
    Manchester, UK
    Posts
    236
    As has been stated, in conductors, electrons do have an important role in thermal conduction, and this is what lies behind the Wiedemann-Franz law.

    In insulators, phonons transport heat from one place to another. An aspect of this that I have found interesting, is that what gives rise to thermal resistance in insulators is the scattering of phonons - phonons can "collide" with each other and, in crystals, they will also be scattered by defects in the crystal structure. However, if one had a perfect crystal with no defects then there would be no defect scattering. Also, if the vibrations in a crystal lattice were harmonic (as opposed to anharmonic), there would be no phonon/phonon scattering either, as such interactions can only occur through anharmonic effects. A crystal of that sort would have no thermal resistance and infinite thermal conductivity!
    Reply With Quote  
     

  15. #14  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by JonG View Post
    As has been stated, in conductors, electrons do have an important role in thermal conduction, and this is what lies behind the Wiedemann-Franz law.

    In insulators, phonons transport heat from one place to another. An aspect of this that I have found interesting, is that what gives rise to thermal resistance in insulators is the scattering of phonons - phonons can "collide" with each other and, in crystals, they will also be scattered by defects in the crystal structure. However, if one had a perfect crystal with no defects then there would be no defect scattering. Also, if the vibrations in a crystal lattice were harmonic (as opposed to anharmonic), there would be no phonon/phonon scattering either, as such interactions can only occur through anharmonic effects. A crystal of that sort would have no thermal resistance and infinite thermal conductivity!
    Interestlng. Unfortunately, chemical bonds do not have harmonic (=parabolic shaped?) potential wells. Though I suppose that if only the first few vibrational states are excited, i.e. at the bottom of the well, they might be close to harmonic. If that were true, one might expect thermal resistance would decline at very low temperatures. Does this happen?
    Reply With Quote  
     

  16. #15  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    It would be ironic if thermal superconductivity is only possible at absolute zero.
    exchemist likes this.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  17. #16  
    Forum Junior
    Join Date
    Sep 2011
    Location
    Manchester, UK
    Posts
    236
    Quote Originally Posted by exchemist View Post
    Interestlng. Unfortunately, chemical bonds do not have harmonic (=parabolic shaped?) potential wells. Though I suppose that if only the first few vibrational states are excited, i.e. at the bottom of the well, they might be close to harmonic. If that were true, one might expect thermal resistance would decline at very low temperatures. Does this happen?
    In a perfect insulator crystal, thermal conductivity would rise (and resistivity fall) as the temperature is reduced. However, in real crystals, this behaviour doesn't persist down to very low temperatures. At very low temperatures, the effects of lattice defects would overshadow the component due to anharmonic behaviour. A plot of thermal conductivity against temperature would then show a peak. For germanium, the peak is at around 20 K. (The electronic conductivity of a semiconductor is very low at such temperatures).
    Last edited by JonG; October 16th, 2013 at 07:24 AM.
    Reply With Quote  
     

  18. #17  
    exchemist
    Join Date
    May 2013
    Location
    London
    Posts
    3,414
    Quote Originally Posted by JonG View Post
    Quote Originally Posted by exchemist View Post
    Interestlng. Unfortunately, chemical bonds do not have harmonic (=parabolic shaped?) potential wells. Though I suppose that if only the first few vibrational states are excited, i.e. at the bottom of the well, they might be close to harmonic. If that were true, one might expect thermal resistance would decline at very low temperatures. Does this happen?
    In a perfect insulator crystal, thermal conductivity would rise (and resistivity fall) as the temperature is reduced. However, this behaviour doesn't persist down to very low temperatures. At very low temperatures, the effects of lattice defects would overshadow the component due to anharmonic behaviour. A plot of thermal conductivity against temperature would then show a peak. For germanium, the peak is around at around 20 K. (The electronic conductivity of a semiconductor is very low at such temperatures).
    How fascinating, thanks.
    Reply With Quote  
     

  19. #18  
    Forum Junior
    Join Date
    Sep 2011
    Location
    Manchester, UK
    Posts
    236
    Quote Originally Posted by Strange View Post
    It would be ironic if thermal superconductivity is only possible at absolute zero.
    There are ironies concerning absolute zero:

    First law of thermodynamics:
    You can't win, you can only break even.

    Second law of thermodynamics:
    You can only break even at absolute zero.

    Third law of thermodynamics: You can't get to absolute zero !
    Strange likes this.
    Reply With Quote  
     

Similar Threads

  1. Covering one's heat signature in space
    By kojax in forum Physics
    Replies: 5
    Last Post: March 14th, 2014, 08:26 AM
  2. need help with heat
    By richie401 in forum Physics
    Replies: 2
    Last Post: April 7th, 2012, 06:49 AM
  3. heat
    By numb3rs in forum Astronomy & Cosmology
    Replies: 3
    Last Post: March 17th, 2008, 11:30 AM
  4. So what is a good way to make tons of heat?
    By itstemo1 in forum Physics
    Replies: 7
    Last Post: September 16th, 2006, 01:43 AM
  5. Heat limit: highest heat
    By chamilton333 in forum Physics
    Replies: 3
    Last Post: March 30th, 2006, 04:01 PM
Tags for this Thread

View Tag Cloud

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •