So you know, what the second law is doing, in other words, it's putting these restrictions on how well or how effectively we can convert heat into work in the case of the engine, or work into heat extracted in the case of a refrigerator.

你们知道，在热机中，热力学第二定律的作用，换句话说，就是给热量,转化为功的效率,施加限制,或在制冷剂中，对抽取热量,进行限制。

麻省理工公开课 - 热力学与动力学课程节选

And so, by and large, until this freon was invented by Midgley, there wasn't a good gas that had the right properties to be used for a refrigerant.

因此，总的说来，直到Midgley发明氟利昂，没有一个气体,能被很好的用作制冷剂。

麻省理工公开课 - 固态化学导论课程节选