middle flue damper

例句：

1. 1. The middle flue damper is used to control the flow of exhaust gases from the furnace.
   中间烟道调节器用于控制炉膛废气的流动。
2. 2. The manufacturer recommends that the middle flue damper be replaced every five years.
   制造商建议每五年更换一次中间烟道调节器。
3. 3. During maintenance, the technician found that the middle flue damper was damaged and needed to be repaired.
   在维护期间，技术人员发现中间烟道调节器损坏了，需要修理。