Flow measurement plays an important role in daily life and manufacture. Plus temperature,pressure and level, the four values are the basic physical value and it is important to test and monitor them.
Flow rate refers to the amount of fluid that flows in a given time. When i open water faucet, we can watch the flow velocity will be depended on the size of valve opened. And water flow rate in a closed pipe will be depended on pipe size,velocity and flow time.
In industry production, flow is needed to measure for controlling manufacturing process.
In energy project, flow/heat meter can be used to measure thermal energy.
In petrochemical industry, flow meter is also used to measure oil and gas.
In municipal administration system, flow rate is used to calculate how much water is used by each family. And flow rate is measured by differet water flow meter, including mechnical water flow meter, ultrasonic water flow meter, electromagnetic water flow meter. The flow rate will be used as evidence for charging.
For different countries and different area and different era, different flow rate unit is used. Now the often used flow rate unit includes cubic meter,liter,gallon,etc.