ORIFICE AND JET FLOW EXPERIMENT

Orifice and Jet Flow Meter Sarmiento, Yvone M. CHE131L – Chemical Engineering Laboratory 1 / A03 1st term of A.Y. 2017-2018

Mapúa Institute of Technology at Laguna Malayan Colleges Laguna

ABSTRACT The

where,

experiment

performed

was

about

the

g = gravitational acceleration

measurement of the flow of fluid using an orifice and H = water elevation above the orifice

jet flow meter. The trajectory of the jet was measured by getting the horizontal and vertical distance from the orifice. The coefficient of velocity and discharge was calculated by the derived formula. Bernoulli equation was the basis of the calculation of the coefficient of velocity while the flowrate equation was the basis of the coefficient of discharge. The results of the experiment concluded that the distance of the fluid from the orifice and water level in the vessel affects the coefficient of velocity and discharge.

Figure 1. Illustration of fluid leaving the orifice. Accounting for the energy losses present, the

INTRODUCTION Measuring and controlling the flow of fluid entering

discharge velocity is modified by a coefficient of velocity, Cv .

and leaving is very important in fluid dynamics. There

 =  2 .2

are many measuring devices for fluid flows. One of the measuring devices is the orifice. Orifice plates

After the fluid exits the orifice, the jet flow drops in

restricts the flow of the fluid and causes pressure

free fall due to the forces of gravity. Figure 2 shows

drop. These plates also help to determine the validity

the trajectory of jet with a constant head tank. The

of the Bernoulli’s equation.

vertical dropping distance Y from the starting point

The Bernoulli equation predicts the horizontal jet velocity of the fluid leaving the orifice at the vena contracta as illustrated in Figure 1. It is defined as,

 = 2 .1 Experiment 1. Orifice and Jet Flow Meter A03 CHE131L –

is:

 = 1   .3 2 By: Sarmiento, Yvone M. BS in Chemical Engineering

EXPERIMENT OBJECTIVES

1.

Operate an Orifice and Jet Flow instrument using a hydraulic bench.

2.

Determine

the

coefficient

of

velocity

and

coefficient of discharge under various constant heads for a given orifice diameter. 3.

Properly compare jet trajectories with that by theory of mechanics.

4.

Determine the effect of modifying the mass flow rate of water to the coefficient of discharge of the orifice.

Figure 2. Trajectory of the jet from constant head tank METHODOLOGY Coefficient of velocity, C v , can also be defined as the ratio of actual velocity to the theoretical velocity.

   = ℎ  / .4  = 2 Deriving t, from Eq.3, and substituting it to Eq.4 will give a definition of coefficient of velocity as,

 .5 = 12 √ The coefficient of discharge, Cd, is measured by getting the time it will take to fill up a certain volume.

Materials 1.

Stopwatch

3.

500mL Beaker

4.

12-inch Ruler

Procedures

1.

  =   = ℎ     =     =  .6 4 2

Place the apparatus on the Bench and adjust for leveling.

3.

Connect the Bench outlet to the apparatus inlet.

4.

Adjust the overflow pipe to obtain a required level in the tank.

5.

Open the water supply valve to obtain a steady flow with minimum overflow.

6.

Wait until the water level in the tank and jet profile is stable before adjusting the tips of the probes to be in line with the center of the jet.

7. Further derivation will give the expression of C d as,

Clip on a graph paper on the probe board behind the probes.

2.

It can also be defined as the ratio of the actual flowrate to the theoretical flowrate.

Hydraulics Bench

2.

Record the tip of the probe profile (upper tips) as well as Y = 0 mark.

2

8.

Record the volume of flow using a stop watch and the bench measuring tank or

Distance from the graph, mm X1 = 50, Y1 = ? X2 = 100, Y2 = ? X3 = 150, Y3 = ? X4 = 200, Y4 = ? X5 = 250, Y5 = ? X6 = 300, Y6 = ? X7 = 350, Y7 = ? X8 = 400, Y8 = ?

Table 1.1.Tabulated results and calculation of flow

rate (1x10-5m3/s)

Trial

Trial 1

2

3

4

5 Water Level H, mm Volume, L

1

2

3

4

5

410

390

370

350

250

0.5

0.5

0.5

0.5

0.5

0

0

0

0

0

5

4.5

4.5

5.5

8

13

12.5

14.5

14.5

21

Time, s

33.38

35.81

36.90

38.54

46.22

24

25.5

26.5

27.5

45

1.498

1.396

1.355

1.297

1.082

39

41.5

44.5

46.5

67

Flow rate, (x10-5) m3/s

58

59.5

63.5

67.5

99

79

83.5

89.5

92.5

138

104

108.5

117.5

122.5

182

measuring cup.

DATA AND RESULTS

Technical Data of the Equipment

Orifice Diameter

: 3mm

Trajectory probe

: 8, stainless steel

Maximum constant head: 420 mm Cylinder diameter

: 200 mm

The following table below shows the gathered and calculated data:

Table 1.2. Tabulated Results of Distance from the graph, mm

Distance from the graph, mm X1 = 50, Y1 = ? X2 = 100, Y2 = ? X3 = 150, Y3 = ? X4 = 200, Y4 = ? X5 = 250, Y5 = ? X6 = 300, Y6 = ? X7 = 350, Y7 = ? X8 = 400, Y8 = ?

Trial 1

2

3

4

5

0

0

0

0

0

5

4.5

4.5

5.5

8

13

12.5

14.5

14.5

21

24

25.5

26.5

27.5

45

39

41.5

44.5

46.5

67

58

59.5

63.5

67.5

99

79

83.5

89.5

92.5

138

104

108.5

117.5

122.5

182

3

Table 1.3. Tabulated Results of Coefficient of velocity,

ANALYSIS, INTERPRETATION, & CONCLUSION

Cv The results in Tables 1.1-4 shows how varying water

Coefficient of velocity, Cv

Trial

level affects the coefficient of velocity and coefficient of discharge of the fluid. By looking at Eq.5, the

1

2

3

4

5

Cv,1

-

-

-

-

-

Cv,2

1.104

1.194

1.225

1.140

1.118

Cv,3

1.027

1.074

1.024

1.024

1.035

in the vessel. As the fluid gets farther away from the

Cv,4

1.008

1.003

1.010

0.991

0.943

orifice, both vertically and horizontally, the coefficient

Cv,5

0.989

0.983

0.974

0.953

0.966

of velocity decreases. The coefficient of discharge

Cv,6

0.973

0.985

0.979

0.947

0.953

Cv,7

0.972

0.970

0.962

0.946

0.942

Cv,8

0.969

0.972

0.958

0.939

0.938

coefficient of velocity varies with change in the horizontal distance of fluid from the orifice, the vertical distance of the jet from the orifice, and the water level

decreases as the water level decreases.

The

coefficient of discharge is affected by the volume of the water in the vessel. The volume of the water determines the flowrate which is used to calculate the coefficient of discharge. Some errors that can be Table 1.4. Tabulated Results of Coefficient of

observed is the measurement of the distance of the

discharge,Cd

trajectory of jet and the inconsistent inlet flow of the fluid in the vessel. Trial

Coefficient of discharge, Cd Cd

1

2

3

4

5

0.75

0.71

0.71

0.70

0.69

REFERENCES Geankoplis, C.J., (1993). Transport Processes and rd

Unit Operations, 3 ed. Englewood Cliffs, New Jersey 07632: Prentice-Hall, Inc.

Trajectory of Jet Chemical Engineering Laboratory 1 Manual

0

M M , E -50 C I F I R O-100 M O R F-150 Y E C N-200 A T IS D

50 100 150 200 250 300 350 400 500

APPENDICES

For F low Rate (as i n Table 1.1): (a) Flow rate DISTANCE X FROM ORIFICE, MM

〖 〖

〗 〗

EXP1: Qact = 1.498x10 ^(-5) EXP2: Qact = 1.396x10 ^(-5)



Actual flow rate

  =    Equation 2 Actual Volumetric Flow Rate

EXP3: Qact = 1.355x10 ^(-5)

〖 〖

〗 〗

EXP4: Qact = 1.297x10 ^(-5) EXP5: Qact = 1.082x10 ^(-5)

Qact = 33.0.53L8s x 1000L 1m3 Qact =. − ⁄ 4

For C oefficient of Velocity (a s in Table 1.3): 

Coefficient of velocity

 =  √ 0.100m =. Cv,2 = 12 √XYH = 12 √0.005mx0. 410m

For C oefficient of Dis charg e (as in Tab le 1.4): 

Coefficient of discharge

  =   =   √ 1.498x10−5 m3⁄s Cd = π(0.003m) 2 m 4 2x9.81 s2 x0.41m  =.

5