Flow Measurement · Glossary

What is Mass Flow Rate?

Symbol: ṁkg/h, kg/s, t/hFlow Measurement

Mass flow rate is the mass of fluid passing a point per unit time. It does not change with pressure or temperature.

Mass Flow Rate Explained

Mass flow is the quantity that matters for reactions, energy balances and custody transfer, because mass is conserved while volume is not.

Coriolis meters measure mass flow directly. Thermal mass meters measure gas mass flow. Other meters calculate it from volumetric flow and a measured or calculated density.

Mass Flow Rate Formula

ṁ = ρ × Q

ṁ	mass flow rate (kg/s)
ρ	fluid density (kg/m³)
Q	volumetric flow rate (m³/s)

Example: 10 m³/h of water at 998 kg/m³ is 9980 kg/h.

Calculators for Mass Flow Rate

CalculatorMass Flow to Volume Flow CalculatorFree online calculator with formula and worked example.CalculatorGas Density CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Mass Flow Rate?

Mass flow rate is the mass of fluid passing a point per unit time. It does not change with pressure or temperature.

Why is mass flow preferred for gases?

Gas volume changes strongly with pressure and temperature. Mass flow stays the same, so it gives a true quantity without correction.

Can a DP meter measure mass flow?

Yes. The orifice equation gives mass flow from DP and density. With live pressure and temperature compensation the density is updated continuously.

Learn more on the blog

Types of flow meters

A practical guide on instrumentationblog.in with more detail on mass flow rate and how it is applied on real plants.

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More Flow Measurement Terms

Flow termReynolds NumberReynolds number is the ratio of inertial to viscous forces in a flowing fluid. It shows whether pipe flow…Flow termLaminar FlowLaminar flow is smooth flow in parallel layers with no mixing between them, found at low Reynolds numbers.Flow termTurbulent FlowTurbulent flow is chaotic flow with eddies and mixing across the pipe, found at high Reynolds numbers.Flow termVelocity ProfileVelocity profile is how flow velocity varies across the pipe, from near zero at the wall to a maximum…Flow termBernoulli's EquationBernoulli's equation states that pressure, kinetic and elevation energy along a streamline add up to a…Flow termBeta RatioBeta ratio is the bore diameter of an orifice, nozzle or venturi throat divided by the pipe internal diameter.

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