dT/dp is mu JT. So for a real gas like air, this is a positive number. It's not zero.

所以对于像空气这样的真实气体，这是一个正数，不等于零。

麻省理工公开课 - 热力学与动力学课程节选

This needs to be stressed that this is the ideal gas case. Now regular gases, real gases fortunately as I said, don't obey this.

需要强调的是这是对理想气体而言的,普通气体，真实气体，就像我说过的,不遵循这个规律，这是非常重要的。

麻省理工公开课 - 热力学与动力学课程节选

Real refrigerators actually work with liquids that go into gases so use the latent heat of the liquid, so it doesn't really work like the Joule-Thomson expansion. So this is real.

液体变成气体来工作,以运用液体的潜热，所以这不是,真正像焦耳-汤姆逊膨胀一样工作,这是真实的气体，不像焦耳。

麻省理工公开课 - 热力学与动力学课程节选

When you expand a real gas into vacuum, the temperature goes down.

当一个真实气体，向真空膨胀咱的时候温度会下降。

麻省理工公开课 - 热力学与动力学课程节选

u=0 And it's approximately equal to zero for all real gas processes.

在所有理想气体绝热过程中Δ,对真实气体近似为零。

麻省理工公开课 - 热力学与动力学课程节选

Pressure has dropped out of the picture completely here. So there is no p dependence here.

理想气体的H只是温度的函数,这对于真实气体来说是。

麻省理工公开课 - 热力学与动力学课程节选

This is real, unlike the Joule coefficient which is very small so that most gases have tiny Joule coefficients. So if you do a Joule experiment, you hardly measure a temperature change. With real gases, here you do actually measure it. You can feel it with your finger on your bicycle tire.

系数那样小以至于,大多数气体的焦耳系数,都很小，所以如果你做焦耳实验,很难测量出温度的变化,对于真实气体，你可以测量它，你能通过手指按在,自行车轮胎上来感觉到它。

麻省理工公开课 - 热力学与动力学课程节选

If you have a real gas and you write du is Cv dT and your path is not a constant volume path, then you are making a mistake. But for an ideal gas, you can always write this. And this turns out to be very useful to remember.

对于真实气体，如果其变化过程,不是恒容的，du=Cv*dT就不成立，但对于理想气体,这条规则永远成立,这一点非常有用，请记住。

麻省理工公开课 - 热力学与动力学课程节选