Exp. No :............ Date :............

DETERMINATION OF PIPE FRICTION FACTOR Aim:

To determine the friction factor (f) of the given pipes.

Apparatus:

U – tube manometer connected across a pipe line, Stop Watch, Collecting tank, etc.

Observation :

l = Length of Pipe = ______ m

d = Diameter of Pipes = ______ cm and ______ cm

A = Area of collecting tank = ______ x ______ = ______ m2

ρm = Density of mercury = 13600 kg/m3

ρw = Density of water = 1000 kg/m3

Graph

Theory:

For the flow of water through a horizontal pipe of uniform size which have two pressure taps

located at desired locations, the total head of the fluid particle on a stream line at the cross section of first

tap is given by Bernoulli’s theorem as,

1 ConstantZ2g

V

ρg

p1

2

11

At the second tap, the total head of the fluid particle is again given by Bernoulli’s theorem as,

2 Constant Z2g

V

ρg

p2

2

22

Equation (1) and (2) would be equal if there is no frictional loss in the pipe. Fluid friction results in loss of

energy of the fluid particle. By adding the term hf to equation (2) to account for loss of energy due to

friction, we get,

Determination of Pipe Friction Factor

Aerospace Engineering Department, IIST Page 2

f2

2

221

2

11 hZ2g

V

ρg

pZ

2g

V

ρg

p

Where p1 and p2 are pressures; V1 and V2 are velocities; Z1 and Z2 are the elevation of fluid

particles at section (1) and (2) respectively.

For a horizontal pipe of uniform diameter, Z1 = Z2 and V1 = V2

Hence, ρg

pph 21

f

hf is also given by Darcy-Weisbach equation,

d g 2

V l fh

2

f

The difference in pressure head

ρg

pp 21 between the two taps (1) and (2) is determined by using a U-

tube manometer.

1

ρ

ρh

ρg

pph

w

m

m

21

f

Where, ρm = density of the manometric liquid.

ρw = density of the fluid (water).

hm = manometric level difference in m of water.

The value of f is also determined by drawing graph hf vs g

V

2

2

.

From this graph the value of K =d

lf is obtained. By substituting the values of l and d , f can be

determined.

Experimental rig:

The experimental set up consists of two pipes of different diameters. Each pipe has two pressure

taps at the desired locations. The pressure taps were connected to a U – Tube mercury manometer. The

flow of water through a pipeline is regulated by operating a control valve which is provided in main

supply line, for measuring the head loss. The length of the pipe is considered as the distance between the

two pressure taps on it. Actual discharge through pipe line is calculated by collecting a desired volume of

water in a collecting tank at the desired duration of time.

Area averaged velocity of water, V =

a

tHA

a

Q /

Where,

A = Area of tank.

H = Height of water collected in tank.

t = Time required to collect the water up to a height “H” in the tank.

a = Area of pipe.

Determination of Pipe Friction Factor

Aerospace Engineering Department, IIST Page 3

Q = Discharge through pipe.

Procedure:

1. Note down the diameter of pipe (d).

2. Note the density of manometric liquid (ρm) and that of fluid (water) flowing through the pipe i.e.

(ρw).

3. Connect the U – tube manometer to the corresponding pipe in between two pressure tappings.

4. Start the pump and adjust the control valve in pipe line for required discharge.

5. Measure the pressure difference at two points 1 & 2 of a pipe by means of a U– tube manometer.

6. Note the time taken for ‘H’ cm rise of water in the collecting tank.

7. Determine the velocity of flow (V) and frictional head loss (hf) by using appropriate equations.

8. Determine the friction factor (f) in pipe by using Darcy – Weisbach formula.

9. Change the flow rate by adjusting the control valve & repeat the process for different flow rates.

10. Find out the friction factor (f) the pipe by plotting the graph Hf Vs g

V

2

2

.

11. Find out the Reynold’s number of flow and from Moody’s chart find the Friction Factor.

12. Plot a graph Reynolds number (Re) Vs friction factor (f).

Determination of Pipe Friction Factor

Aerospace Engineering Department, IIST Page 4

Observation Table :

Fric

tio

n f

acto

r fr

om

Mo

od

y’s

char

t

f -

R

eyn

old

’s

Nu

mb

er

Re -

fric

tio

n

fact

or

f -

Ve

loci

ty

of

flo

w

V

m/s

Act

ua

l D

isch

arge

Qac

t

m3/s

Fric

tio

na

l H

ead

Lo

ss

hf

Tim

e f

or

H c

m r

ise

of

wat

er

in C

olle

ctin

g Ta

nk

Me

an

t s

t 2

s

t 1

s

Man

om

ete

r re

adin

gs

hm

= h

2-h

1

mm

of

Hg

h2

mm

h1

mm

Sl.

No

:

1 2 3 4 5 1 2 3 4 5

Dia

met

er

of

Pip

e

D

m

Determination of Pipe Friction Factor

Aerospace Engineering Department, IIST Page 5

Friction factor,f can also be found from the Moody’s chart.

The basic chart plots Darcy–Weisbach friction factor against Reynolds number for a variety of

relative roughness and flow regimes. The relative roughness being the ratio of the mean value of

roughness for the pipe to the pipe diameter, ie d

ε.

The value of for the GI pipe is 0.00015 m.

Reynolds Number, Re =

Vd

Where, = Density of the fluid.

= Dynamic viscosity of fluid.

V = Velocity of flow.

d = Diameter of the pipe.

Result :

Friction factor for the pipe,

Diameter of pipe

Friction factor from

experiment

Friction factor from

Moody’s chart

The graphs Hf Vs g

V

2

2

and Re Vs f are plotted.

Inference :

Determination of Pipe Friction Factor

Aerospace Engineering Department, IIST Page 6