variable-head variable-area flowmeter

例句：

1. 1. The variable-area flowmeter is used to measure the flow rate of fluids.
   可变面积流量计用于测量流体的流速。
2. 2. The variable-area flowmeter was installed at the entrance of the factory.
   可变面积流量计安装在工厂入口处。
3. 3. The variable-area flowmeter is a crucial component in the process control system.
   可变面积流量计是过程控制系统中的关键部件。