M . V . H A R I S H B A B U

M A N O J K U M A R T R I P A T H I

M E D A R A M E T L A K R I S H N A K A L Y A N

M O H A M M A D S A L I M U D D I N

Determination of Friction Factor

EXPERIMENT 1

BATCH 1 GROUP 4

Aim

To determine the Friction Factor in case of water flowing through Galvanized (G.I) and P.V.C pipes.

Apparatus

1 inch G.I pipe

1 inch P.V.C pipe

Nipples (short and long)

Ball valves

Manometer

Bucket

Scale

Stop watch

Theory

The Darcy Weisbach equation relates the head loss or

pressure loss due to friction along a given length of pipe

to the average velocity of the fluid flow.

The Darcy Weisbach equation is a phenomenological

formula which is obtainable by dimensional analysis.

The Darcy Weisbach equation contains a

dimensionless factor called as the Darcy’s Friction

Factor.

Contd.

Where

hf is the head loss or pressure loss.

L is the length of the pipe.

D is the hydraulic diameter of the pipe(=4A/S).

V is the average velocity of fluid flow(=Q/A).

f is the Darcy’s Friction Factor.

Contd.

The friction factor f is not a constant and depends on the

parameters of the pipe and the velocity of the fluid flow.

It may be evaluated for given conditions by the use of

various empirical or theoretical relations, or it may be

obtained from published charts. These charts are often

referred to as Moody diagrams.

Experimental Setup

Procedure

An inverted U tube manometer is connected between two points on the pipe as shown in the figure. Here, the manometric fluid is water.

Difference in level of water in the two limbs of the manometer gives the pressure difference between those two points.

Flow rate of water, Q is determined by measuring the water flowing out in a given interval of time, say 10 seconds.

Video

Observations

S.No. hf x10-2

(in m)ln hf Flow rate, Qx10-4

( in m3/s)Velocity ( in m/s)

ln v

1 3.8 -3.27 2.61 0.516 -0.661

2 6.0 -2.85 3.29 0.649 -0.431

3 9.5 -2.35 4.14 0.817 -0.201

4 16 -1.76 5.37 1.061 0.058

5 21 -1.56 6.15 1.214 0.193

6 30.4 -1.19 7.39 1.460 0.378

For G.I. Pipe

Diameter of the pipe ,D = 2.54 cm

Cross Sectional Area, A = 5.0645 cm2

Plot(G.I. Pipe)

Intercept: -1.9477

So,

ln (f L/2Dg)= -1.9477

f = 0.038

P.V.C Pipe

S.No. hf x10-2

(in m)ln hf Flow rate, Q

X10-4( in m3/s)Velocity ( in m/s)

ln v

1 13.5 -2.002 5.544 1.13 0.119

2 19.2 -1.650 6.574 1.34 0.296

3 22.1 -1.480 7.064 1.44 0.366

4 26.9 -1.112 7.800 1.59 0.464

5 36.1 -1.018 9.076 1.85 0.612

6 41.2 -0.886 9.665 1.97 0.678

For P.V.C. Pipe,

Diameter of the pipe, D= 2.5 cm

Area of the pipe, A= 4.906 cm2

Plot (P.V.C pipe)

Intercept = -2.213

So,

ln (f L/2Dg)= -2.213

f = 0.0286

Result

Darcy’s friction factor, obtained for

1). G.I. Pipe : f=0.0383

2). PVC Pipe : f=0.0286

Values expected from Moody’s Plot:

For Reynolds No. of the order of 104 ,

In case of G.I. pipe, f = 0.032

In case of PVC pipe, f = 0.020

Results(contd.)

• Moody’s plot :

Contd.

0.037910.037920.037930.037940.037950.037960.037970.037980.03799

0.038

0 20000 40000

Fr

icti

on

Fa

cto

r

Reynolds No.

• When friction factor is plotted against Reynolds No., for a

GI pipe, following plot was obtained and it is very much in

agreement with the actual Moody’s chart, for the order of

Reynolds No. around 104

Thank You