University of Baghdad
College of Engineering
Department of Chemical Engineering.
Lab. of
Chemical engineering
Name of experiment
ORIFICE METER
…3rd…/class/ A..
Name of the student :
Data of experiment:
Data of delivery:
Written by : ‫عبد العزيز محمد‬
Introduction:
It is widely to measure the airspeed of aircrafts, speedboat speed and for fluid flow
measurement in industrial application. Pitot tube measures the pressure point in
contact.
Theory of operation
The basic pitot tube consists of a tube pointing directly into the fluid flow. As this
tube contains fluid, a pressure can be measured; the moving fluid is brought to rest
(stagnates) as there is no outlet to allow flow to continue. This pressure is
the stagnation pressure of the fluid, also known as the total pressure or (particularly
in aviation) the pitot pressure.
The measured stagnation pressure cannot itself be used to determine the fluid flow
velocity (airspeed in aviation). However, Bernoulli's equation states:
Stagnation pressure = static pressure + dynamic pressure
The dynamic pressure, then, is the difference between the stagnation pressure and
the static pressure. The dynamic pressure is then determined using a diaphragm
inside an enclosed container. If the air on one side of the diaphragm is at the static
pressure, and the other at the stagnation pressure, then the deflection of the
diaphragm is proportional to the dynamic pressure.
In aircraft, the static pressure is generally measured using the static ports on the
side of the fuselage. The dynamic pressure measured can be used to determine
the indicated airspeed of the aircraft. The diaphragm arrangement described above
is typically contained within the airspeed indicator, which converts the dynamic
pressure to an airspeed reading by means of mechanical levers.
Instead of separate pitot and static ports, a pitot-static tube (also called
a Prandtl tube) may be employed, which has a second tube coaxial with the pitot
tube with holes on the sides, outside the direct airflow, to measure the static
pressure.
If a liquid column manometer is used to measure the pressure difference
Construction and Working:
,
The pitot meter consists of a tube pointing directly toward the flow. The fluid
enters through the impact hole and there can one or two other holes in the pitot
tube, which are the static pressure source.
fig:1
For a simple pitot tube (shown in fig:1) we should arrange one another pressure
sensing element to measure the static pressure. The axis of tube measuring the
static pressure should be perpendicular to the boundary and free from burrs so that
the boundary is smooth.
The pitot-static tube that having the static pressure inlet is shown below.
A pitot tube is a simple round cylinder with one end opened with a small hole and
other end enclosed. The fluid flowing through the pipeline enters the pitot tube and
rest there. There is another chamber within the pitot tube filled with fluid with
static pressure. A diaphragm separates both the chambers.
The differential pressure is measured between both the pressures gives the dynamic
pressure. The difference in level between the liquid in the tube and the free surface
becomes the measure of dynamic pressure. The flow rate, like other devices, is
calculated from the square root of the pressure.
In calculating the flow rate from the pressure, the calculation is dependent on such
factors as tube design and the location of the static tap. The Pitot-static probe
incorporates the static holes in the tube system to eliminate this parameter.
Measuring the static pressure and the impact pressure are connected to the proper
differential pressure meter for the determination of flow velocity and thus the flow
rate.
Experimental procedure
1. turn on the dir blower at speed 3.
2. fix pitot tube at the side of the duct by sliding it on the ruler to the position
(zero), record the initial (data) level manometer
3. change the position of pitot tube by (2mm) each time and record the in dined
distance (Razo) in cmH20.
4. repeat (3) until pitot tube reaches the position of the other side of the duct.
5. Turn off the blower and do the calculation.
materials
air Equipment -Air duct -blower - Pitot tube contact with U - tube manometer
r
h1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
h2
27
30.7
31.4
31.9
32.2
32.3
32.5
32.8
32.7
32.7
33
32.8
32.1
32.1
28
27
delta
16
11.8
11.5
10.8
10.5
10.4
10.1
9.9
9.9
10
9.5
9.8
10.1
10.5
14.6
15.7
11
18.9
19.9
21.1
21.7
21.9
22.4
22.9
22.8
22.7
23.5
23
22
21.6
13.4
11.3
deltarefrance
0
7.9
8.9
10.1
10.7
10.9
11.4
11.9
11.8
11.7
12.5
12
11
10.6
2.4
0.3
delta air
Ux
0
7.89052
8.88932
10.08788
10.68716
10.88692
11.38632
11.88572
11.78584
11.68596
12.485
11.9856
10.9868
10.58728
2.39712
0.29964
0
12.44235
13.20638
14.06855
14.4804
14.61511
14.94656
15.27082
15.20652
15.14195
15.65106
15.33485
14.682
14.41258
6.857951
2.424652
18
16
14
Ux
12
10
8
6
4
2
0
0
0,2 0,4 0,6 0,8
1
1,2 1,4 1,6 1,8
r,m
2
2,2 2,4 2,6 2,8
3
Discussion:
Inviscid fluid is flowing along a pipe of varying cross section, then the pressure is
lower at constrictions where the velocity is higher, and higher where the pipe
opens out and the fluid stagnates. Many people find this situation paradoxical when
they first encounter it ,higher velocity, lower pressure. The well-known Bernoulli
equation is derived under the following assumptions:
 Fluid is incompressible (density r is constant);
 Flow is steady:
 Flow is frictionless (t = 0);
For compressible fluids, the volumetric flow rate must include information about
temperature and pressure in order to relate the volume and mass flow rates. Mass
flow rate it is the quantity of mass flowing through a system at a given time. For
most liquids, the mass flow rate and the volumetric flow rate are equivalent since
the density of a liquid is typically an insensitive function of temperature and
pressure. However, the density of an ideal gas which is compressible is a strong
function of both temperature and pressure ( =P/RT). This means that mass flow
rate and volumetric flow rate are not always equivalent for gases. We can relate
the two by specifying temperature and pressure for volumetric flow rates.
References
1. ^ Pitot, Henri (1732). "Description d'une machine pour mesurer la
vitesse des eaux courantes et le sillage des vaisseaux" (PDF). Histoire
de l'Académie royale des sciences avec les mémoires de
mathématique et de physique tirés des registres de cette Académie:
363–376. Retrieved 2009-06-19.
2. ^ Darcy, Henry (1858). "Note relative à quelques modifications à
introduire dans le tube de Pitot" (PDF). Annales des Ponts et
Chaussées: 351–359. Retrieved 2009-07-31.
3. ^ Venturi effect and Pitot tubes | Fluids | Physics | Khan Academy,
retrieved 2019-12-15
4. ^ "How Aircraft Instruments Work." Popular Science, March 1944,
pp. 116.
5. ^ Willits, Pat, ed. (2004) [1997]. Guided Flight Discovery - Private
Pilot. Abbot, Mike Kailey, Liz. Jeppesen Sanderson. pp. 2–48–2–
53. ISBN 0-88487-333-1.