Fall 2003
EML4141L Experiment I
Frictional Losses in Piping Systems
This experiment will make use of the TQ H16 "Losses in Piping Systems" apparatus. It
requires a controlled water flow rate, which will be provided by the weigh tank apparatus
(TQ H1). By running water through the piping system on the apparatus at a known flow
rate, you are required to:
1) Measure the friction factor for flow through the 13.7 mm and 26.4 mm diameter
straight sections of pipe. Generate the Moody (friction) chart for a large enough
range of the Reynolds number to cover laminar, transitional, and turbulent
regimes. The suggested upper limit of the Reynolds number is 15,000.
2) Compare the measured friction factors with those predicted for smooth pipes. Can
the pipewall be considered smooth?
3) Determine the minor loss coefficient (K) for proprietary 90° elbow.
Note : K 
P
1
V 2
2
Experimental Procedure:
1. Connect the inlet tube of pipe system with the sump outlet of the bench. Direct the
outlet tube of pipe system into the inner tank of the bench
2. Turn on the power button of the bench to make the water circulated
3. When the pivot arm becomes horizontal, add weights to the hanger. At the same
time, start timing using a stopwatch
4. When the beam returns to the horizontal position, stop timing.
5. Record the time and the weights
6. Record the pressure loss using the U-tube manometers on pipe system
7. Turn off the power button
8. Repeat steps 2-7 using different weights
INTRODUCTION AND OBJECTIVES
The objective of the lab is to make use of the "Losses in Piping Systems" apparatus to
measure the friction factor and compare with the theoretical value. The water source is
provided by a weigh tank, which also provides a means to measure the mass flow rate
using a stop watch and a correlation factor of 3: 1 mass advantage provided by the lever
arm. The task in running the experiment was to complete the following:
. Measure the friction factor for flow through 13.7mm and 26.4mm diameter straight
sections of pipes and generate the Moody chart for a range of Reynolds numbers up
to 15,000.
. Compare the measured friction factors with those predicted for smooth pipes in
the laminar, transition and turbulent regions.
. Determine the minor loss coefficient (K) for a proprietary 90° elbow.
Assumptions:
. Fully developed flow in the pipes
. Water temperature = 72°F (approximately 22°C)
PRINCIPLES
Determination of the friction factor first requires a value for the head loss to be
obtained. The head loss represents the conversion of mechanical energy to unwanted
thermal energy. The thermal energy is generated as the flow interacts with the surface of
the pipe producing heat and thus producing a pressure loss in the pipe. The pressure loss
for the experiment is determined through the use of a manometer. The manometer
reading was a direct measurement of the head loss that occurred between the two points
of interest. An energy balance is shown below in Equation 1 for the determination of the
head loss via energy per unit weight of flowing liquid between two locations of piping.
P V2
P V2
(1)
( 1  1  z1 )  ( 2  2  z2 )  H
 g 2g
 g 2g
The above equation can be simplified for a horizontal pipe (z1 =z2) and for a pipe of
constant diameter (V1 =V2) at steady state flow rate, thus reducing the head loss to the
change in pressure due to the frictional effects from the pipe wall
Definitions:
P
L V2
H 
,H  f
g
D 2g
(2)
( dp / dx ) D
f 
V 2 / 2
In the above, f is the Moody or Darcy friction factor. For a fully developed laminar flow,
the theoretical Darcy friction factor is determined as follows:
64
f la min ar 
Re D
(3)
VD
Re 

Where  

is the kinematic viscosity.

It is noted that the friction coefficient, also called Fanning friction factor is defined as,
Cf 
w
1
V 2
2
(4)
f
.
4
The above is valid for fully developed flows. In the regions of interest in the
experiment, due to the location of port 8 a discussion of this topic is appropriate. Port 8 is
located approximately 0.33 m to the right of an expansion section in the tubing. The
entrance length (distance until the flow becomes fully developed) can be determined for
For fully developed laminar circular pipe flow, C f 
the laminar and turbulent cases using the textbook Fluid Mechanics by White. For
laminar flow the entrance length is a function of Reynolds number shown in Equations 5
and 6.
Le
 0.06 Re D
Laminar flow
(5)
D
Le
 4.4 Re1/D 6
Turbulent flow
(6)
D
Laminar flow can be expected only for Reynolds numbers less than 2300, thus the
entrance length may be as long as 138D. The diameter of the pipe at port 8 is 26.41mm,
thus giving an estimate of the laminar entrance as 3.64m. In the turbulent region
experimental data shows the velocity profile becomes fully developed within 25 to 40
diameters. Estimating the entrance length for the turbulent region using the best case
scenario of 25D gives a length of 0.66m. The conclusion from the discussion above is
that the flow at port 8 is not fully developed and that this assumption introduces error into
the results. The exact flow condition is unknown and the calculations will be performed
using equations that are dependent on the fully developed assumption being satisfied to
complete the analysis. The theoretical (smooth pipe) friction factors were determined
using equations for fully developed flow in the laminar and turbulent regions shown in
Equations 3 and 7 respectively. The laminar friction factor is independent on the surface
roughness, thus the experimental and theoretical values are both calculated from Equation
3. The turbulent equation is termed the Blasius equation and is valid up to Re = 105. For
the fully developed turbulent flow, we have the following equations for smooth pipes:
0.316
f turbulent 
ReD<2x104
Re1/D 4
0.184
f turbulent 
ReD>2x104
Re1/D 5
Or
f  1/(0.790ln Re D  1.64) 2
3000<ReD<5x106