You've got to put more pressure on one side than the other if you want to push that gas through the throttle, right? So this is where the time scale issue comes into play.

如果你想让更多的气体通过节流阀,应该使一边的压强,大于另一边，是吗？所以这就是,时间尺度发挥作用的地方。

麻省理工公开课 - 热力学与动力学课程节选

You take a throttle valve, which consists of some sort of porous plug between two cylinders that is insulated. There is insulation here.

有一个节流阀，它由一些多孔的塞子组成,这些多孔塞在两个绝热的汽缸之中,这里是绝热的，底下也是绝热的。

麻省理工公开课 - 热力学与动力学课程节选