return-flow tunnel

例句：

1. 1.The engineer designed a return flow tunnel to improve the efficiency of the cooling system.
   工程师设计了一个回流隧道来提高冷却系统的效率。
2. 2. In this project, we need to install a return flow tunnel to ensure the safe operation of the machinery.
   在这个项目中，我们需要安装一个回流隧道以确保机械设备的安全运行。
3. 3. The return flow tunnel is crucial for maintaining the cleanliness of the environment.
   回流隧道对于保持环境的清洁至关重要。