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 .
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