Volume flowrate refers to the volume of fluid passing through the flow section per unit time, referred to as flow rate, and is usually represented by Q. (Applicable not only to liquids, but also to gases. Gas volume flow specifically refers to the volume of gas flowing through the delivery pipeline per unit time.)

There are two main ways of expressing volumetric flow: volume under working conditions and volume under standard conditions.

They all refer to the volume at a certain pressure and temperature. In particular, the volume under standard conditions refers to the volume of gas when the pressure is one standard atmosphere and the temperature is 0°C (or 20°C).

The volume flow rate can be calculated by various formulas. One of the common formulas is qv=V/t=u×A, where qv is the volume flow rate, V is the unit flow volume, t is the unit time, and u is the average flow velocity in the pipe, A is the cross-sectional area of the pipe.

It should be noted that since the volume flow rate is based on measurement at standard temperature and pressure, when the medium temperature and pressure deviate from the set state, the indication value measured by the instrument may change.