What Is a Variable Area Flow Meter?
A variable area flowmeter measures the amount of a fluid, such as gas or air, that moves from one location to another.
Since there are various types of variable area flowmeters (rotameters), it is necessary to select the appropriate one according to the required measurement accuracy, operating environment, and intended use.
As a result of the wide variety of area flow meters available, the level of technology is rapidly improving.
These instruments are used to measure the flow rate of liquids or gases, purge fluids or gases, etc.
Uses of Variable Area Flow Meters
Variable area flowmeters are mainly used to measure the flow rate of liquids or gases, purge fluids, or gases.
Specific use cases include the following:
- Flow rate measurement when injecting chemicals
- High-pressure flow measurement on offshore oil platforms
- Measuring the supply of city gas to households
Since there are two measurement methods, contact and non-contact, it is important to select the method that best suits the application and purpose of use.
- Non-contact type using magnetic fields/sound waves, etc.
- Contact type that measures directly through an object
Principle of Variable Area Flow Meters
A variable area flowmeter consists of a tapered tube and jigs (joints, etc.).
The tapered tube is pushed up to the top due to the force caused by the pressure difference before and after the fluid (liquid, gas, or vapor) flows through it.
Since the distribution area of the gap between the tapered tube and the above increases, the pressure difference decreases and the float rests at the position where its effective weight and the force due to the pressure difference are in equilibrium.
At this point, the area of the flow rate determined by the position of the float in the tapered tube is equal to the flow rate through it, and the flow rate can be measured by detecting this position.