Short Answer:
A mass flow meter measures the mass of the fluid flowing through a pipe, while a volumetric flow meter measures the volume of the fluid. Mass flow meters give readings in units like kilograms per second (kg/s), whereas volumetric flow meters show values in liters per second (L/s) or cubic meters per hour (m³/h).
The main difference is that mass flow meters consider fluid density, making them accurate even when temperature or pressure changes. Volumetric meters, on the other hand, do not adjust for density, so their readings can vary with changing fluid properties.
Detailed Explanation:
Difference between mass flow meter and volumetric flow meter
Flow meters are essential devices used to measure how much fluid (liquid or gas) is moving through a system. Depending on the requirement, we use either mass flow meters or volumetric flow meters, and each serves a different purpose.
Mass Flow Meter:
A mass flow meter directly measures the mass of the fluid flowing through the pipe. It tells how much matter is actually passing, regardless of the fluid’s pressure or temperature. Mass flow is very important in chemical reactions, fuel monitoring, or any system where the actual amount of substance matters.
The most common type is the Coriolis mass flow meter. It works by vibrating a tube through which the fluid flows. The flow of fluid causes twisting in the vibration due to the Coriolis effect, and this twist is directly related to the mass flow rate. Another type is the thermal mass flow meter, which uses heat sensors to detect how much heat the flowing fluid carries away, indicating the mass flow.
Key Points:
- Measures mass in kg/h or lb/min
- Accurate even with changing temperature or pressure
- Best for gases, chemical mixtures, and precise processes
- More expensive and complex than volumetric meters
Volumetric Flow Meter:
A volumetric flow meter measures the volume of fluid passing through a point in a given time. It tells how much space the fluid occupies, not its actual weight or mass. This is suitable when the fluid’s density stays the same or does not matter much for the application.
Common types include:
- Turbine flow meters, where flow spins a rotor
- Ultrasonic flow meters, which use sound waves
- Orifice meters, which measure pressure drop
- Rotameters, which measure float height in a tapered tube
Volumetric flow meters are easy to use and affordable but can give wrong readings if the fluid’s density changes due to temperature or pressure.
Key Points:
- Measures volume in L/min or m³/h
- Simpler and cheaper
- Affected by temperature and pressure changes
- Common in water supply, HVAC, and general piping
Main Differences:
What is measured:
- Mass flow meter: Measures actual mass (kg/s)
- Volumetric flow meter: Measures volume (L/s)
Effect of fluid properties:
- Mass flow meter: Unaffected by temperature or pressure
- Volumetric flow meter: Readings may change if density changes
Accuracy:
- Mass meters are more accurate for changing conditions
- Volumetric meters are accurate only if density is constant
Cost and complexity:
- Mass meters are more expensive and need more setup
- Volumetric meters are cheaper and simpler
Application:
- Mass meters used in fuel, gas, and chemical dosing
- Volumetric meters used in water, oil, and basic systems
Conclusion:
A mass flow meter measures the actual mass of a fluid, while a volumetric flow meter measures how much space the fluid occupies. The key difference lies in accuracy under varying fluid conditions. Mass flow meters give precise readings regardless of temperature and pressure, making them suitable for advanced industrial applications. Volumetric meters are simpler and widely used in everyday systems where exact mass is not required.