“Venturimeter, Orificemeter,

Notches & weirs, Pilot tubes”

PREPARED BY :

JAY PANCHAL 140123109007

GUIDED BY : Prof. Aditya singh

Gandhinagar Institute of Technology.

Venturi Meter

Venturimeter is a device used for measuring the rate of flow of fluid flowing through the pipelines.

Working It consist of a short converging conical tube which

has a total included angle of 21 ± 1° leading to a cylindrical portion of short length, known as throat.

It s followed by diverging section known as diffuser having total included angel 5°to 7°.

The pressure difference measure between the entry section 1 and the throat section 2, usually by means of a U-tube manometer.

The axis of venturimeter may be horizontal or inclined or vertical.

Area of flow in divergent section is increased gradually to avoid separation of flow and reduce friction losses.

The value of coefficient of discharge varies from 0.95 to 0.99.

Disadvantages of Venturi meter:

Highly expensive

Occupies considerable space Cannot be altered for measuring pressure

beyond a maximum velocity.

Orifice meter• It may be installed in pipeline with a

minimum of trouble and expense

Working Orifice meter is device used to determine the rate of

flow through pipe. It consist of flat circular plate which has a sharp

edged circular hole called orifice. It is fixed concentric to pipe. The orifice diameter is generally kept half of the

diameter of the pipe. It is based on the same principle as explained in

venturimeter. The value of Cd varies between 0.60 to 0.65. It is a economical and less space is requred for

fitting.

Difference between an Orifice meter and Venturimeter

• For venturi tube, there is no contraction-– Area of the jet is always equal to the area of the throat

and is fixed

While for the orifice the area of the jet is a variable

(less than Ao, the area of the orifice)• For venturitube

Cd = Cv (Cc=1.0)

While for the orifice, it is much more affected by variations in Cc than it is by variations in Cv

Notches A notches is defined as an opening in the side of a

vessel or tank in such a manner that the liquid surface in the tank.

A notch is generally made of metallic plate. It is used for measuring the discharge rate of a liquid

from a small channel or tank.

Weir

A weir is basically an obstruction in the flow path in an open channel.

The weir will cause an increase in the water depth as the water flows over the weir.

In general, the greater the flow rate, the greater will be the increase in depth of flow, The height of water above the top of the weir is the measurement usually used to correlate with flow rate.

Pitot tube

A pitot tube is a simple device used for meausuring the velocity of a flow at the required point in a pipe or steam.It is also called as impact tube or stagnation tube.

Operation• The basic pitot tube consists of a tube pointing directly

into the fluid flow. As this tube contains fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue.

• This pressure is the stagnation pressure of the fluid, also known as the total pressure or (particularly in aviation) the pitot pressure.

• The measured stagnation pressure cannot itself be used to determine the fluid flow velocity (airspeed in aviation). However, Beronulli’s equation states:

• Stagnation pressure =

static pressure + dynamic pressure

Refrences

B.L. SINGHAL

(ATHE :TECH-MAX)• http://www.engineeringcivil.com

• http://discoverarmfield.com

Thank You…