You break the seal between them and feel the thing get cold, for example, right.

如果你买了制冷或加热包,你打开它们之间的封条。

麻省理工公开课 - 热力学与动力学课程节选

You break the seal between them and feel the thing get cold, for example, right.

如果你买了制冷或加热包,你打开它们之间的封条。

麻省理工公开课 - 热力学与动力学课程节选