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

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