Hi,

I made a mistake. You say that temperature is a measure of average kinetic energy, not proportional to it. If you'd like to see an example of when this is not true, take a look at the Nuclear Spins section of the Wikipedia entry on negative temperature at http://en.wikipedia.org/wiki/Negative_temperature. There the energy involved is potential. This is not at all a criticism of your video, just me being pedantic.

James

Yep. I actually did see that article during my research, but decided, since I wasn't really going quantum or dealing with entropy, to stick to the classical definition of temperature. Thanks!

David

Great Stuff! Incredibly impressive stuff from such clever young people! Keep up the great work! The students at my school where I teach were very impressed and they are 18 years old and want to know how you are cleverer than them........Our video "Convection, heat transfer, who cares?" was also in the comp! You can see it here...hope you like it.. http://www.fqxi.org/community/forum/topic/2136

Dear Kristen,

I watched your cool video and I liked it a lot! I learned very interesting things about heat and refrigerators and conditioning air. Good luck in the contest!

Victor

Hi David,

I think I watched your video two or three times in a row and then looked at my refrigerator with new eyes. It is cool to see how through basic processes like condensation and vaporization make it work. I was reading a bit about cooling techniques afterwards and found this article. Apparently there is a refrigerating method that uses the magnetocaloric effect to create the heat pump needed for the cooling process - which could save a lot of energy in the future. I thought you might find it as interesting as I did.

I hope we make it both among the finalist and wish you best of luck! Of course we will vote for you and hope you do the same - if you haven't done yet. We would greatly appreciate it :)

Madeleine

    That is very interesting. I'm surprised I didn't run into that during my research! I did rate your video, immediately after commenting; thanks so much for rating mine!

    David

    Dear Kristen,

    I really enjoyed your video. What I appreciated most was that while I am well-versed in the physical principles involved, I had never taken the time to sit down and see *exactly* what how the refrigerator was transferring the heat. The detailed explanation is not simple, and yet you did an excellent job of walking us through the basic principles and relevant details. Out of all the videos I have seen, I shall be watching this one again for my own edification.

    Thank you.

    Kevin Knuth

    PS I am happy to see that I am Community Vote #10... good luck in the finals!

      David and Kristen,

      Thank you for watching my trilogy of videos "This Is Physics" and for the comment you left on the forum of part 2. I am glad to see that your amazing video has gotten at least 10 votes and is doing so well in the community ratings!

      The first two parts of my trilogy have already gotten at least 10 community votes, but part 3, "Physics Into Darkness", is still one vote short... You probably already gave ratings for all 3 parts... but just in case you haven't gotten to rating part 3, it would be quite appreciated! Here's the direct link:

      http://www.fqxi.org/community/forum/topic/2197

      Thank you, and good luck in the finals!

      Marc

      Hi Kristen,

      Nice video and a very clear explanation of the underlying thermodynamics involved. Is there a special reason to use HFC-134a as the working fluid? I assume it has some good properties that make it well suited for refrigeration. Alternatively are there other fluids that can be used?

      Another cool way of cooling things is via a peltier cooling device which also leads to heat transfer but via an electrical current.

      As a non-physics comment we also used a Kevin Macleod piece for the music in our video ("Moment of Inertia...."). I've seen several other videos that use his music.

      Good luck with the contest.

      Mike, Max, Dan, Simon, Doug

        HFC-134a started to become common in the 90s as a replacement for the banned Freon-12. It does not have the the ozone-depleting properties of Freon, but unfortunately it is a potent greenhouse gas, so it is likely to be banned eventually as well. Like any good refrigerant, HFC-134a has favorable thermodynamic properties, and it is also relatively non-toxic and noncorrosive. There are various alternatives, including other HFC blends, ammonia, and even water. It is actually possible to use air as a refrigerant, but this is not very efficient since there is no phase change. Madeleine Richter posted this link about an interesting new method that takes advantage of the magnetocaloric effect.

        Thanks for the rating and comment!

        David

        9 days later

        Great video about refrigeration... Video is awesome explaining the thermodynamics...

        Please go through my video also and rate it and give me your valuable suggestions... The topic of my video is - PHYSICS THE ODYSSEY...

        Regards

        8 years later
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