To determine minor losses due to gradual enlargement and construction. by using fluid friction apparatus

Object

To determine minor losses due to gradual expansion and constriction in the pipe diameter.

Apparatus

Fluid friction apparatus; Hydraulics bench and Stop watch.

Fig. Fluid friction apparatus

Theory

1. Gradual Expansion:
   

The value of loss coefficient for gradual expansion is function of the two radii, as shown below

In the fluid friction apparatus, D1 = 17 mm and D2 = 28.4 mm, hence D1/D2 = 0.6, hence Ke

should be 0.15.

For sake of verification of the value of loss coefficient due to gradual expansion in the pipe diameter we use the relationship

V 2

where

hle

 K 1

2g

e

(1)

hle = loss of head due to gradual expansion in the pipe diameter

V1 = velocity of flow at section-1 = Q/A1

where,Area of flow at section-1 =

A  2

41

1

d

 3.14

4

(1.7)2

 2.27

cm2

(since d1 = 17 mm = 1.7 cm)

Putting values in Eq.(1),

K  2g

1

V

e

2

.hle

2  981

(Q / 2.27)2

.hle

 10108.2 hle

Q2

(2)

1. Gradual Constriction:
   

Similarly, the value of loss coefficient for gradual constriction is function of the two radii, as shown below

In the fluid friction apparatus, D1 = 28.4 mm and D2 = 17 mm, hence D2/D1 = 0.6, hence Kc
should be 0.06.

For sake of verification of the value of loss coefficient due to gradual constriction in the pipe diameter we use the relationship

V 2

where

hlc

 K 2

2g

c

(3)

hlc = loss of head due to gradual constriction in the pipe diameter

V2 = velocity of flow at section-2 = Q/A2 where,Area of flow at section-2 =

A  2

2

d

42

 3.14

4

(1.7)2

 2.27

cm2

(since d2 = 17 mm = 1.7 cm)

Putting values in Eq.(3),

K  2g

2

V

c

2

.hlc

2  981

(Q / 2.27)2

.hlc

 10108.2 hlc

Q2

(4)

Procedure

1. Fill tank of hydraulics bench with clean water.
   
2. Connect the fluid friction apparatus with hydraulics bench.
   
3. Open the valve(s) that allows flow to the section under consideration and close all the irrelevant valves of the pipe friction apparatus.
   
4. Connect the two ends of the tubes to the pressure tapping nipples at the either side of the pair of the elbows and the manometer.
   
5. Slightly open the Flow control valve at the hydraulics bench.
   
6. Remove air bubbles from the tubes by opening the Vent valve and Drain valves of differential manometer.
   
7. Read the heads in the monometers corresponding to the pressure along entry and exit of the sections under consideration.
   
8. Collect water in the volumetric measuring section of the hydraulics bench. Read the volume collected as well as time taken to collect that volume of water.
   
9. Open the Flow control valve at the hydraulics bench slightly more for taking new reading.
   
10. Repeat steps 7 and 8 to observe new readings.
    
11. Carry out computations as per table below and compare the average value of Ke and
    

Kc with those given in literature as discussed above.

Observations and Calculations

Comments