A mass flow meter, also known as an inertial flow meter, is a device that measures the mass flow rate of a fluid as it passes through a tube. It is a device that measures the flow rate of a fluid (liquid or gas) as it passes through it. The mass flow rate is the amount of fluid that moves past a fixed place per unit time. Unlike standard flow meters, which measure volume, mass flow meters measure the mass of the substance passing through them. This is particularly beneficial in applications where the fluid density varies or measurement accuracy is required.
The mass flow meter does not measure the volume per unit time (e.g. cubic meters per second) that passes through the device; rather, it measures the mass per unit time (e.g. kilograms per second) that flows through it.
The volumetric flow rate is the mass flow rate divided by the fluid density. If the density remains constant, the relationship is simple. If the fluid’s density varies, the relationship becomes more complex. The density of a fluid, for example, can fluctuate depending on its temperature, pressure, or composition. The fluid could alternatively be a mixture of phases, such as a fluid containing entrained bubbles. The relationship between sound velocity and regulated liquid concentration allows for the determination of actual density.
Mass flow meters operate based on various principles, including thermal, Coriolis, and differential pressure.
- Thermal mass flow meters measure the heat transfer from a heated sensing element to the fluid. The rate of heat transfer is proportional to the mass flow rate.
- Coriolis mass flow meters use the Coriolis effect, where a vibrating tube is influenced by the fluid flowing through it. The phase shift between the inlet and outlet vibrations is proportional to the mass flow rate.
- Differential pressure mass flow meters measure the pressure drop across an obstruction in the flow path, such as an orifice plate or a venturi tube. The pressure drop is related to the flow rate.
Each type of mass flow meter has benefits and drawbacks, based on the fluid characteristics, flow range, accuracy requirements, and installation conditions. They have uses in a variety of industries, including chemical processing, oil and gas, pharmaceuticals, food and beverage, and others.
