tag:blogger.com,1999:blog-31189917.post3749712345521024014..comments2024-03-11T04:40:23.756-07:00Comments on The Blog of Phyz: Adiabatic cooling puzzleDean Bairdhttp://www.blogger.com/profile/17681829220589441713noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-31189917.post-45109375820678195962010-02-19T08:15:41.597-08:002010-02-19T08:15:41.597-08:00Whenever I expand the chamber, nothing happens at ...Whenever I expand the chamber, nothing happens at all, both T and P remain the same as before expansion. Something is definitely wrong with the applet.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-31189917.post-89869611727280937702010-02-15T13:48:26.703-08:002010-02-15T13:48:26.703-08:00Thanks, all. I'm assured this behavior is cons...Thanks, all. I'm assured this behavior is consistent with the principles of free expansion and the Joule-Thompson Effect. No sim bug!<br /><br />@Paul, slow and reversible... I remember such things from my old Thermo class, now that you mention it. Years of exposure to energetic and impatient students appears to have taken its toll.Dean Bairdhttps://www.blogger.com/profile/17681829220589441713noreply@blogger.comtag:blogger.com,1999:blog-31189917.post-10514992426456550252010-02-15T10:51:53.008-08:002010-02-15T10:51:53.008-08:00Hi Dean
You expanded the piston faster than the s...Hi Dean<br /><br />You expanded the piston faster than the speed of sound in the gas (Or at least nearly supersonicaly).<br />I started with the piston completely compressed, added three squirts of light atoms. Expanded it at a rate such that atoms collided with the piston and it cooled nicely. Then again with heavy atoms, expanding it slowly it cooled nicely. Expanding it as rapidly as possible led to no collisions and no loss of temperature. Our usual rules do not apply to supersonic piston motion.Paul Dohertynoreply@blogger.comtag:blogger.com,1999:blog-31189917.post-67238716619894188162010-02-14T09:53:31.592-08:002010-02-14T09:53:31.592-08:00i suspect a faulty simulation. might try the davi...i suspect a faulty simulation. might try the davis gas simulation <br />donAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-31189917.post-73539582199179040832010-02-13T19:24:48.112-08:002010-02-13T19:24:48.112-08:00Well, there's bigger and there's receding....Well, there's bigger and there's receding. I assume that the simulation models one of those idealized slow expansions, so that the speed of the walls is taken to be zero. But... T should still change, as I see it.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-31189917.post-20354836104067779612010-02-13T18:33:14.518-08:002010-02-13T18:33:14.518-08:00What you expect is correct, and their simulation d...What you expect is correct, and their simulation does as such. The problem is that as you make the space smaller, all of the particles in dV are impacted by the moving wall, and gain energy. As you make the space bigger, only the particles which happen to be striking the left wall lose energy, so the isothermal expansion you see is an artifact of statistical mechanics. Run the same simulation with a couple moles, or expand and contract it very slowly, and this problem will go away.Kenneth Finneganhttps://www.blogger.com/profile/09597995268728038585noreply@blogger.comtag:blogger.com,1999:blog-31189917.post-59437126915705610342010-02-13T18:00:56.356-08:002010-02-13T18:00:56.356-08:00Thermo's not my first love either, but a thoug...Thermo's not my first love either, but a thought.<br />T prop. to KE.<br />No reason why KE should decrease When Volume goes up. <br />jdUnknownhttps://www.blogger.com/profile/05991909194855682769noreply@blogger.com