To determine the Cd for a Venturi meter and To determine the Cd for an Orifice meter..

Object: a) To determine the Cd for a Venturi meter.

Fluid Friction Apparatus

Apparatus Required:

• Fluid friction apparatus; Hydraulics bench and Stopwatch.
  

Theory:

• Venturi meter is an apparatus used for measuring discharge of a liquid flowing in a pipe. A venturimeter in its simplest form consists of.
  

1. A converging cone
   
2. Throat
   
3. A diverging cone
   

Fig. 2 Venturi meter (diagrammatic)

Let

a1 = cross-sectional area at the entrance = 338.6 mm² = 3.386 cm² a2 = cross-sectional area at the throat = 84.6 mm² = 0.846 cm² h = difference of head between entrance and throat

Qac = Cd . Qth

or Cd = Qact / Qth

where Qac = V/t

a1a2

a2  a2

2gh

1

2

and

Qth 

In the fluid friction apparatus, a1 = 338.6 mm² = 3.386 cm² and a2 = 84.6 mm² = 0.846 cm², hence

Qth

or Qth



 38.7

(3.386)(0.846). 2  981

3.3862 0.8462

h

h

Procedure:

Observations:

Results & Comments:

Object:b) To determine the Cd for an Orifice meter.

Fluid Friction Apparatus

Apparatus Required:

• Fluid friction apparatus; Hydraulics bench and Stopwatch.
  

Theory:

• Orifice meter is an apparatus used for measuring discharge of a liquid flowing in a pipe.
  

D = diameter of the pipe = 28.4 mm = 2.84cm

d = diameter of the orifice = 18.5 mm = 1.85 cm

A = cross-sectional area of the pipe = 6.3347 cm²

Fig. Orifice meter (diagrammatic)

Q  a

2gh





1 D  

 d 4 

  

(1)

Q_act = C_d x Q_th = Cd a

2 gh





1  D  

 d 4 

  

Procedure:

Observations:

Results & Comments:

or