And so instead of defining efficiency the way you've got it written there, I'm going to define what's called something different for a refrigerator which is called the coefficient of performance.

现在我们不用,效率的那个定义，我给出一个,有关制冷机的,新的定义,叫做制冷系数。

麻省理工公开课 - 热力学与动力学课程节选