What is Variable Area Flow Meter?
A variable area meter is a meter that measures fluid flow rate by allowing the cross-sectional area of the device to vary in response to the fluid flow, causing some measurable effect that shows the rate. Variable Area Flow Meter are used to measure the volume flows of liquid and gasses.
a) Volumetric Flow Meter
A flow meter is a device to measure the amount of liquid, gas or vapor flow through a pipe. Most flow meters are designed to measure the speed or velocity at which the fluid flows through a pipe. They use measured velocity or speed along with the pipe’s inner cross-sectional area to calculate volume, or the amount of fluid passing through the system during a given time period (i.e. 30 liters per minute).
Flow meters are often the combination of a primary element, transducer, and transmitter. Fluid sense by the transducer that passing through the primary element, allowing the transmitter to generate a measurable flow signal. These three components are frequently combined, therefore an actual flow meter may be the combination of few devices.
b) Variable Area Working Principle
Flow meters are used in fluid systems (liquid and gas) to measure or indicate the rate of flow of the fluid. When a flow control valve equipped, they can also control the rate of flow too. This variable area principle consists of three basic elements: A uniformly tapered flow tube, a float, and a measurement scale. A control valve added to fulfill a closed loop flow control system.
Variable area flowmeters feature an upright tapered measuring tube, wider end up, in which a specially shaped float moves freely up and down, therefore, the medium flows through the tube from bottom to top. In so doing, it raises the float until there is an annular gap between the wall of the tube and the float and equilibrium of the forces applied to the float has been achieved.
c) Advantages of Variable Area Flow Meter
– No external power require
– Suitable for both liquids and gasses
– No upstream and downstream straight run require
– Generally maintenance free
– Available with contact or current output
– Simple construction and lost cost
d) Disadvantages of Variable Area Flow Meter
– Vertical installation
– High-pressure loss
– High solids content could block the measuring float
– Pressure, temperature, and density dependent
– Sensitive to pulsation or vibration
– Wearing from abrasive media