Question

Draw neat sketch of Rotameter and explain its working principle.

Answer 1

Rotameter: - A variable-area flowmeter is one where the fluid must pass through a restriction whose area increases with flow rate. The height of the float is directly proportional to the flowrate

Neat diagram of rotameter

Working of Rotameter: - • It consists of a vertical tube with conical cone or shape. • It is constant pressure drop variable flow meter in which float is free to move within it the fluid flows through the tube from bottom to the top • When no fluid is flowing the float reset at the bottom of the tube • The float is made of such a diameter that it completely blocks the inlet section • When a flow starts in a pipeline and the fluid reaches the float, the buoyancy effect of fluid makes the float lighter • The float has a density greater than that of flowing material so that the buoyancy effect alone is not sufficient to lift the float • The float remains close until the pressure of flowing material (fluid flow or Drag) + buoyancy effect of fluid exceeds the downward pressure due to the weight of the float

 

A= Buoyancy effect

• The float then rises and floats within the flowing medium (Pipe) in proportional to the flow rate • The float reaches a stable position in the tube when the upward force exerted by the flowing fluid (i.e + ) equals the downward gravitational force exerted by the weight of the float. • Increase in the flow rate causes the float to rise higher in the tube • Decrease in the flow rate causes the float come down to the lower level • The float gives reading on a calibrated scale which is on glass tube and the flow rate can be determined by direct observation of the metering tube