6循环( Cycle) If a system returns to its initial state at the end of the process it is said a system have undergone a cycle. 系统经历了一系列状态变化过程,又回到了原来状态, 称为热力循环6.循环 (Cycle) If a system returns to its initial state at the end of the process, it is said a system have undergone a cycle. 系统经历了一系列状态变化过程，又回到了原来状态， 称为热力循环