translation.en: You move that up and down with a little bit of energy but now you're only shifting the air down to the hot end and up to the cold end, down to the hot end and up to the cold end.
translation.zh: 用少量的能量来移动它 但是能够做到将空气下移到热端，上移到冷端， 再下移到热端，上移到冷端。