Experiment on friction factor determination produced by pipes and fittings.

1. EXPERIMENT NO. 4 | GROUP 3 | MAY 24,2016 1
CHE150-1L Chemical Engineering Laboratory 1
4th
Quarter AY 2015-2016
FRICTION FACTOR (Fluid Flow Set-Up)
Ricky Jay C. Gomez1
1
Student, Mapúa Institute of Technology, School of Chemical Engineering and Chemistry
ABSTRACT
Determining the amount of frictional dissipation is vital in different processes industries because it determines how
much mechanical energy is lost during a process. There are two types of friction being accounted, the skin friction
and form friction. Skin friction refers to the friction when the fluid is being contacted with the pipe’s inside surface.
The form friction refers to the friction produced by valves and fittings. The total frictional dissipation is produced by
both types of friction. A dimensionless wall stress is quantified to describe the amount if frictional dissipation. This is
the frictional factor. In laminar flow, the friction factor is only a function of Reynolds Number. In turbulent flow, the
friction factor is a function of Reynolds Number and relative roughness. Relative roughness represents the average
roughness or depth of the surface irregularities. The amount of the mechanical energy in a fluid flowing through a
pipe is equal to its pressure head. Experimentally, Fanning equation is used to compute for the factor based in
experimental data. From the results of the experiment, the trial that has a greater Reynolds number, has the lower
friction factor computed. This satisfies the trend of the curves in friction factor chart. The slope of the curves in the
chart have negative slopes, which suggests the inverse proportionality between the Reynolds number and the friction
factor. In physical description, this just signifies that as the fluid achieves turbulence at constant relative roughness,
the amount of the resistance in the fluid decreases, thus, friction factor is decrease.
Keywords: friction factor, Fanning equation, skin friction, form friction.
INTRODUCTION
For every engineering process involving piping
systems, pressure drop is affected by the kinetic
energy loss and friction. This friction produces the
pressure drop, which introduces the flow of the fluid.
There are two types of friction: the skin friction and
the other one is the form friction. Skin friction is
generated in unseparated boundary layers; for example,
in straight pipes. If any surface is in contact with a
fluid and a relative motion exists between the surface
and the fluid, the transfer of momentum results in a
tangential stress or drag on the surface that is oriented
parallel to the direction of flow. Form friction is an
energy dissipation that occurs when boundary layer
separates and form wakes; for example, flow through
valves, fittings, and obstruction such as sudden
contraction or enlargement of cross section. Whenever
a fluid changes path to pass around a solid body set in
the flow path, the fluid accelerates and significant

2. EXPERIMENT NO. 4 | GROUP 3 | MAY 24,2016 2
frictional losses consequently occurs because of
acceleration and deceleration of the fluid.
As the fluid flows through a straight pipe or tube, some
of the mechanical energy are lost due to the effect of
friction which is a function of the fluid properties and
the scope of the piping system as well. The total
frictional dissipation is caused by both skin and from
type of friction:
s FF F F   (1)
2
e c f
c
L u
F 4f K K K
D 2g
 
      
(2)
Form friction can be evaluated in terms of loss
coefficient, K, which is defined as the number of
velocity heads lost due to fluids passing through
valves, fittings or any obstructions. Alternately, form
friction can also be estimated in terms of the
equivalent length of a pipe that has the same effect (i.e.
pressure drop due to friction) as the valve, fitting, or
obstruction under in the system considered.
For a fluid being compressed as it enters the pipe from
a source having large diameter compared to that of the
pipe, the value for Kc is 0.5 while for a fluid which
expands as it flows from the pipe to a tank or reservoir
having large diameter, the value for Ke is 1.0.
For a fluid flowing inside pipe, a dimensionless wall
stress is defined so as to describe the frictional loss of
the fluid’s mechanical energy as it flows through a
pipe. This parameter is call the friction factor. It is the
ratio of the wall stress to the inertial force per unit area
that would result from the impingement of a stream of
density and velocity normally against the wall. The
fluid’s amount of friction loss is dependent on its
density, velocity and viscosity and as well as pipe’s
diameter, length and the roughness. The equivalent
roughness of the pipe is also determined to
characterize the average roughness or depth of the
irregularities of the surface.
For a laminar flow (Re < 2100), the friction factor is
only a function of Reynolds Number, which is
represented by the Blasius equation:
16
f
Re
 (3)
For a turbulent flow (Re > 4000), the friction factor is
determined through the use of Churchill equation:
0.9
1 7
4log 0.27
D Ref
   
    
   
(4)
For the mechanical energy balance that accounts the
frictional losses, the total frictional dissipation (F) is
equal to the total pressure drop:
F = −
∆𝑃
𝜌
= Rm (
ρ 𝐻𝑔
ρ
− 1) (
𝑔
𝑔 𝑐
) (5)
To compute for the frictional dissipation
experimentally, Fanning equation is being used which
is a function of friction factor and other fluid and pipe
properties:
2
s
c
4fLu
F
2g D
 (6)
For this experiment, the friction factor of water as the
working fluid should be determined as well as to
determine the effect for the Reynold Number and the

3. EXPERIMENT NO. 4 | GROUP 3 | MAY 24,2016 3
relative roughness on the friction factor of the fluid
flow.
METHODOLOGY
The equipment used in the experiment was the fluid-
flow set-up and the materials used were steel tape,
stopwatch and thermometer. Water was used as the
working fluid.
FIGURE 1: Fluid Flow Set-Up.
The pump was primed and started in order for the fluid
to initiate flowing along the piping system. The length
of the pipeline used was measured. For a time span of
60 seconds, the amount of water collected was
measured and the volumetric flowrate was then
calculated. After getting the volumetric flowrate, the
temperature was determined in order to evaluated the
Reynolds Number with the corresponding fluid
properties at the temperature measured. Also, the
manometer reading was measured. The total friction
losses were calculated from the results gathered, as
well as the experimental friction factor. The
percentage error based on the theoretical value of
friction factor computed. Same procedures were done
for the remaining trials.
RESULTS AND DISCUSSIONS
The data gathered from the experiment are tabulated
below:
V. m3
/s 1.33x10-4
1.25x10-4
U, m/s 1.67 1.57
D. m 10.06x10-3
10.06x10-3
T(o
C) 24.7 24.8
ρ, kg/m3
996.688 996.673
µ, cP 0.9088 0.9063
NRe 18424.91 17369.14
Rm 3 7
F 3.69 8.63
L, m 1.085 1.085
ɛ 4.57x10-5
4.57x10-5
ɛ/D 4.54x10-3
4.54x10-3
fexp 6.13x10-3
0.001623
ftheo 8.66x10-3
8.73x10-3
% error 29.21 85.91
TABLE 1: Tabulated data from the experiment.
From TABLE 1, comparing the theoretical friction
factor calculated for the two trials with respect to their
corresponding Reynolds Number, the trial that has a
higher Reynold Number, has the lower theoretical
friction factor. Referring to the friction factor chart,

4. EXPERIMENT NO. 4 | GROUP 3 | MAY 24,2016 4
which is a plot of Reynolds Number versus the friction
factor, the curves produced have negative slopes. This
just mean that NRe and f are inversely proportional to
each other. Therefore, at a constant relative roughness
of the pipe and as the fluid approaches turbulence, the
value for the friction factor decreases, thus, the
frictional dissipation also decreases. Turbulence in
fluid flow reduces the magnitude of the resistance
experienced by the fluid, so less friction will be
encountered by the fluid. At a high Reynolds Number,
friction factor becomes constant and only dependent to
the relative roughness of the pipe.
Some sources of errors arise in this experiment, which
makes deviations of the experimental value of friction
factor from the theoretical values. One of these might
be the inaccurate reading of the manometer. Reading
the manometer is always a tedious part of the
experiment especially when there is a little to
negligible difference in height. This inaccuracy alone
can make a dramatic effect to the computed friction
factor. Another possible source of error is the
measurement of the time. Obviously, the time gathered
would not be as exact as needed because the
measurement is very manual.
CONCLUSION
The effect of friction has been significant for various
engineering processes. It affects the behavior of the
fluid as it flows through a pipe. When the fluid flows
through a pipe, the amount of mechanical energy lost
due to friction is dependent on different properties of
the fluid as well as on the scope of the piping system.
For a fluid flowing through a pipe of uniform diameter,
the friction dissipation is affected by the density,
viscosity, and velocity of the fluid, and as well as on
the diameter, length of relative roughness of the pipe.
Friction factor is being accounted to describe the
frictional dissipation on the fluid as it flows. At
constant relative roughness and low Reynolds Number,
the friction on the fluid is very high, thus, having a
high friction factor. As the fluid approaches turbulence,
the resistance on the fluid reduces, so the friction
factor is being decreased. This relationship between
Reynolds Number and the friction factor is being
described in the friction factor chart, wherein curves
produced have negative slopes. At high Reynolds
Number, the value of friction factor is constant and
only dependent on the relative roughness of the pipe.
APPENDIX
Sample Computations:
A. Volumetric Flow Rate of Water (V)
V =
𝑉 𝐻2 𝑂
𝑡
=
6 𝐿 (
1 𝑚2
1000 𝐿
)
60 𝑠
= 1.33x10-4
m3
/s
B. Velocity of the Water (u)
U =
𝑉
𝐴
=
8𝑥10−3 𝑚3
𝑠
𝜋
4
(10.06𝑥10−3 𝑚)2
= 1.67 m/s
C. Density of Water (ρH2O)
By interpolation:
T (o
C) ρ (kg/m3
)
15.6 996.4
24.8 ρ
26.7 998.0
ρ = 996.688 kg/m3

5. EXPERIMENT NO. 4 | GROUP 3 | MAY 24,2016 5
D. Viscosity of Water (µH2O)
By interpolation:
T (o
C) µ (cP)
15.6 1.131
24.8 µ
26.7 0.860
µ = 0.9088 cP
E. Reynold Number (NRe)
NRe =
𝐷𝑢𝜌
µ
=
(10.03𝑥10−3 𝑚)(1.67
𝑚
𝑠
)(996.688
𝑘𝑔
𝑚3)
0.9088𝑥10−3 𝑃𝑎−𝑠
= 18424.91
F. Mechanical Energy Due to Friction Loss (F)
F = −
∆𝑃
𝜌
= Rm (
ρ 𝐻𝑔
ρ
− 1) (
𝑔
𝑔 𝑐
)
= (
3
100
m) (
13534
996.688
− 1) (9.8)
= 3.69
G. Experimental Fanning Friction, fexp
F =
2𝑓𝑢2 𝐿
𝑔 𝑐 𝐷
3.69 =
2𝑓1.672(1.085)
(1)(10.03𝑥10−3)
fexp = 6.13x10-3
H. Theoretical Fanning Friction, turbulent
(Churchill Equation)
1
√𝑓
= −4 log[0.27 (
ɛ
𝐷
) + (
7
𝑁𝑅𝑒
)
0.9
]
1
√𝑓
= −4 log[0.27(4.57𝑥10−3) + (
7
18424.91
)
0.9
]
f = 8.66x10-3
I. Percentage Error
% 𝑒𝑟𝑟𝑜𝑟 =
|8.66𝑥10−3
− 6.13𝑥10−3|
8.66𝑥10−3
𝑥100%
=29.2 %
REFERENCES
[1] (n.d.). Retrieved from
https://en.wikipedia.org/wiki/Darcy_friction
_factor_formulae
[2] (n.d.). Retrieved from
http://www.engineeringtoolbox.com/surface
-roughness-ventilation-ducts-d_209.html
[3] (n.d.). Retrieved from
http://www.enggcyclopedia.com/2011/09/ab
solute-roughness/
[4] Geankoplis, C. J. (n.d.). Transport Processes
and Separation Processes Principles.
[5] Perry, R. H., & Green, D. W. (2008). Perry's
Chemical Engineer's Handbook. McGraw-Hill
Companies.
[6] Mapua Institute of Technology. (n.d.).
Chemical Engineering Laboratory Manual Part 1.