Types of orifice plate , Venturi meter , Construction , Working

1. Concentric Orifice plate :

it is used when a good corrosive resistant property is needed  .

2. Eccentric Orifice Plate  :

it is similar to the concentric orifice plate except for the offset hole which is bored tangential to a circle . this type is used to measure the flow rate of suspension .

3. Segmental Orifice plate :

it has a hole which is a segment of a circle it is used with suspension containing more solid particle in it  .

4. Quadrant edge orifice plate  :

The quarter -  circle or quadrant orifice is used for fluid of high viscosity . the orifice incorporates a rounded edge of definite radius which is particular function of orifice diameter .

Venturi - meter :

Venturi meter is a device that is used to measure the rate of flow of fluid through a pipe  .

main parts of venturi meter :

- Converging cone or Diameter ( the area is decreasing ) .

- Throat Diameter ( the area is constant ) .

- Diverging cone ( the area is increasing  ) .

Construction :

1. Converging cone :

- when water is flowing through this cone the area is decreasing therefore the speed of flowing water increases and Pressure Decreases .

2. Throat Diameter :

- When water flowing through this cone the area remains constant therefore the speed of flowing water and Pressure remains constant .

3. Diverging cone :

- When water flowing through this cone the area is increasing , therefore  , the speed of flowing water decreases and Pressure Increases .

Working :

Cross section of throat is less then the cross section of inlet pipe . since the cross section decreases from inlet pipe to throat , the velocity of the fluid increases and hence the Pressure Decreases .

Due to decrease in the Pressure ,a Pressure Difference is created between the inlet pipe and throat of venturimeter   .

 

This Pressure Difference can be measured by placing a differential manometer between the inlet section and throat section . After getting the Pressure Difference flow rate through pipe is calculated  .

Volumetric flow rate of the fluid can be calculated using the following equation .

Q (actual) = Cd  (A1A2/ SQRT(A1^2 - A2^2 ) )SQRT( 2gh )

SQRT = Square Root .

A1 =  Cross sectional inlet area 

A2 = Cross sectional throat area

h = Pressure Heads

g = Gravity

Cd = Coefficient of Discharege .

Qact = Volumetric Flow Rate .