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Mass Flow Measurement

 


What is mass flow measurement


Mass flow meter measures flow rate of the fluid through the pipe. Mass flow meter does not measure the volume. The mass flow rate is the mass of fluid that passes by a fixed point per unit of time. Mass of the fluid can be determine by using this type of flow meter. By measuring the density of fluid this flow meter measures the mass. 

The Mass flow is proportional to density, cross-sectional area through which the substance is flowing, and velocity of fluid. This mass flow meter is very accurate and it is used to measure the flow of gases and fluids. 

Types of mass flow meter


What are the types of mass flow meter 
How mass flow meter work

Coriolis and thermal flow meters are two types of a mass flow meter. A mass flow meter is required for the accurate measurement of the mass related processes such as chemical reaction, heat transfer .

Thermal flow meter




In thermal flow meter a thermostat is used to measures the mass of the fluid flowing in the process, Thermister is inserted in the line in which fluid is flowing, this thermistor is used to neasure temperature. Sofluid is not clogged and thermal flow meter can also measure very low flow rates. 

Thermal flow meter working principle is based on thermal conductivity. Thermal flow meter will introduce heat into the flow stream and it measures the heat dissipation amount in flow stream. This flow meter don't dependent on the density, pressure, or viscosity of the fluid flowing in the stream.

Thermal flow meter can be used to measure the mass flow rate of fluids as well as flow of gases. Basically a thermistor is mounted inside the pipe of flow stream when the fluid passes through it carries the heat away from the thermistor. So when flow rate is high then the thermistor will become cool fastly and increases its resistance. Another thermister is installed in some accurate meters.

Types of thermal mass flow meter
Constant temperature difference

Two temperature sensorsa are used in this type of flow meter one is a heated sensor and other is to measure the gas temperature. Electrical power vonsumed to maintain the temperature difference between two sensors is proportiobal to mass flow rate.


How to install a thermal mass flow meter

 1. It must not be installed where the flow is downward in a vertical pipe.

2. Flow meter should be installed in a way that, it must be full of liquid so no air be trapped inside the tube.

 Advantages of thermal mass flow meter

1. Mass flow directly measures the flow without using pressure and temperature inputs. 
2. This type of flow meter give accurate measurement at very low flow rates. 

3. Pressure drop is less in mass flow meter. 

4. This ttpe of fliw meter is less costly. 
5. This type of flow meter is Maintenance free
6. There is no need for pressure and temperature compensation. 

7. Its installation is easy. 


Applications of thermal mass flow meter

Oil and gas
Power plants
Chemical plants
Water and waste
Metals and mining process
Food and beverage
Pharmaceuticals
Textile industry


Coriolis meter

Corolios mass flow meter is U shaped and it is used to measure fliw of gases and liquids. The fluid will flow through a U shaped tube and tube vibrates and this vibration will be proportional to the fluid flow. Energy and velocity of the fluid resists the vibrating motion of the tube, and that makes it twist sideways. The degree of deflection is linearly and directly proportional to the mass of the fluid that passes through the t

Volumetric flow meters — orifice plates, magnetic flow meters, most of the common types — measure how much volume of fluid passes a point per unit time. But volume changes with temperature and pressure; a kilogram of compressed air takes up very different space at 2 bar versus 7 bar. On a lot of processes, especially anything involving gas, steam, or custody transfer, what you actually care about is mass, not volume. That's where mass flow meters earn their keep.

Why Mass Matters More Than Volume

Take compressed air metering as an example. If you measure volumetric flow with a standard meter, the reading will shift with every change in line pressure and temperature — even if the actual mass of air moving through the pipe hasn't changed at all. For accounting, energy balances, or process control where mass is the real variable (combustion air ratio, fuel gas metering, steam mass balance), a volumetric reading without proper compensation will quietly mislead you.

Mass flow meters solve this by measuring mass directly, sidestepping the need for separate pressure and temperature compensation calculations that volumetric methods require.

Coriolis Mass Flow Meters

This is the workhorse mass flow technology in industry today. The principle exploits the Coriolis effect — the same physics that makes weather systems spiral.

Inside the meter, the fluid is routed through one or two vibrating tubes. When there's no flow, the tubes vibrate symmetrically. Once fluid moves through them, the Coriolis force causes a slight twist or phase shift between the inlet and outlet sides of the tube — the faster the mass flow, the bigger that twist. Sensors on each end of the tube pick up the timing difference, and the transmitter converts that into a mass flow reading directly, with no need for separate density or temperature compensation (in fact, Coriolis meters give you density and temperature readings as a bonus, since both are inherent to how the measurement works).

Where Coriolis meters excel:

  • Very high accuracy — typically ±0.1% to ±0.5% of reading, better than almost any other flow technology
  • Direct mass measurement, no need for density/pressure/temperature correction
  • Works on liquids, gases, and slurries
  • No moving parts in the flow path — good reliability, low maintenance
  • Can also serve as a density meter and, indirectly, a concentration meter

Where they fall short:

  • Expensive compared to orifice or vortex meters, especially in larger line sizes
  • Pressure drop across the meter body can be significant depending on design
  • Sensitive to external vibration and pipe stress if not installed and supported correctly
  • Larger sizes get bulky and heavy — not always practical to retrofit into tight piping

Thermal Mass Flow Meters

Thermal meters work on a completely different principle — they measure how much heat is carried away by the flowing fluid, which is directly related to mass flow rate.

Most designs use two sensing elements: one heated slightly above process temperature, and one measuring the actual process (reference) temperature. As gas flows past the heated element, it carries heat away — more mass flow means more heat loss, and the meter measures either the power needed to maintain a constant temperature difference, or the temperature drop for a constant power input, depending on the design (constant-temperature vs. constant-power mode).

Where thermal meters excel:

  • Excellent for low-pressure gas flows — compressed air, natural gas, biogas, flare gas, nitrogen purge lines
    • ub

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Comments

  1. YEKE China Valve Manufacture5 March 2026 at 01:02

    Very informative article on industrial valves. Helpful for choosing the right valve.
    Check Valve Suppliers in China

    ReplyDelete

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