export flow function

• 出口流量函数

export flow function的用法和样例：

例句

1. The outlet pipe of each pump has a flow gage to conveniently read outlet flow of the pump and know the pump's working condition.
   每个油泵的出油管路上都设有流量计，可以方便的读出油泵的出口流量，随时了解泵的工作状态。