JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Pharmacy II Year PHARMACEUTICAL ENGINEERING Previous Question Paper (September-2021 - R17)

Flow meters are instruments used to measure the rate of flow of fluids (liquids or gases) through pipes or conduits. The choice of a flow meter depends on the fluid properties, flow range, accuracy requirements, and cost.

The common types of flow meters include:

1. Venturi Meter: Consists of a converging section, a throat, and a diverging section. It measures flow by creating a pressure drop proportional to the square of the flow rate.
   Merits: High accuracy, low permanent pressure loss, and ability to handle slurries.
2. Orifice Meter: A thin plate with a hole placed in the pipe. It creates a pressure differential across the orifice.
   Merits: Simple construction, low cost, and easy to install or replace.
3. Pitot Tube: Measures the velocity at a specific point in the pipe by comparing stagnation pressure to static pressure.
   Merits: Very inexpensive, simple to install, and causes negligible pressure loss.
4. Rotameter: A variable area meter consisting of a tapered tube and a float. The float rises as flow rate increases.
   Merits: Direct visual reading, simple design, and constant pressure drop.
5. Turbine Flow Meter: Uses a rotor that spins in the fluid stream; the rotational speed is proportional to the flow velocity.
   Merits: High accuracy, fast response time, and suitable for clean, low-viscosity fluids.
6. Electromagnetic Flow Meter: Operates on Faraday's law of induction for conductive fluids.
   Merits: No moving parts, no obstruction to flow, and unaffected by fluid density or viscosity.

In summary, while Venturi meters offer high efficiency, Orifice meters are preferred for general industrial applications due to cost-effectiveness, and Rotameters provide the convenience of direct flow rate observation.