In a practical context, a flowmeter measures the amount of fluid movement from one point to another.
There are three types of flowmeters commonly used. They are:
1. Differential Pressure Flow Meter
A pipe is blocked by a membrane of known thickness with an opening of known size. The fluid pressure is measured on each side.
The difference in the reading of one side of the blockage to the other is proportional to the distance between the two points.
The volumetric flow rate, viscosity of the fluid, and the diameter of the vessel (pipe), must be known.
Corrections are then made for temperature and pressure to produce a mass flow rate.
2. Thermal Mass Flow Meter
These derive mass from the specific heat capacity of the fluid. The specific heat capacity of the fluid must be given.
Some or all of the flow passes through a tube. An amount of heat is applied to the tube. The change in temperature is observed.
The difference in temperature between the two points indicates the amount of the fluid's energy absorption, which is dependent on the mass moving through the tube.
3. Coriolis Mass Flow Meter
A Coriolis mass flow meter measures mass through inertia. Fluid flows through a vibrating tube.
This movement produces a twisting force proportional to the mass.
The mass flow rate is measured without needing to know the density, specific heat capacity or other knowledge of the fluid flowing inside.
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