fluid lab pressure

1. Fluid Lab
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Method of pressure measurement
Name: Khogr Kamal Ibrahim
Group: 2
Fluid lab.
2021
Kurdistan Regional Government
Sulaimani Polytechnic University
Mechanical engineering

2. Fluid Lab
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Introductin:
Manometer :It is a widely used device for measurement of fluid pressure under
steady state and laboratory conditions. This method involves balancing the
unknown pressure against the pressure produced by a fluid column of known
density. The manometer gives directly the gauge pressure. In order to improve
the resolution on very low-pressure manometers, the indicating tube is
inclined to cause a greater linear movement than a vertical tube. U-tube and
inclined
U TUBE MANOMETERS :-The principles of manometry are most easily
demonstrated in the U tube manometer shown in Figure l. It is simply a glass
tube bent to form the letter U and partially filled with some liquid. With both
legs of the instrument open to atmosphere or subjected to the same pressure,
the liquid maintains exactly the same level or a zero reference. As illustrated in
Figure 2, if a pressure is applied to the left side of the instrument, the fluid
recedes in the left leg and raises in the right leg. The fluid moves until the unit
weight of the flu id as indicated by H exactly balances the pressure. This is
known as hydrostatic balance. The height of fluid from one surface to the other
is the actual height of fluid opposing the pressure.
INCLINED MANOMETERS: Many applications require accurate measurement of
low pressure such as drafts and very low differentials. To better handle these
applications the manometer is arranged with the indicating tube inclined, as in
Figure 6, providing for better resolution. This arrangement can allow 12" of
scale length to represent 1" of vertical liquid height. With scale subdivisions, a
pressure of 0.00036 psi (one hundredth of an inch of water) can be read.

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OBJECTIVE:
The purpose of this experiment is to demonstrate different pressure measurement methods.
Pressure measurement operations will be conducted by using U-tube and inclined tube
manometers. Bourdon tube manometer will be calibrated by using dead weight piston gauge.
THEORY
Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per
unit area over which that force is distributed. It has units of N/m2
or Pa or psi.
The absolute pressure - pabs - is measured relative to the absolute zero pressure - the pressure that
would occur at absolute vacuum. All calculations involving the gas law requires pressure (and
temperature) to be in absolute units.
A gauge is often used to measure the pressure difference between a system and the surrounding
atmosphere. This pressure is often called the gauge pressure and can be expressed as
pg = ps - patm (2)
where
pg = gauge pressure
ps = system pressure
patm = atmospheric pressure
U-tube manometer is widely used to measure pressure difference between two containers or two
points in the system.
Bourdon pressure gage is one of the most commonly used devices. It operates on a principle that
when a pressure acts on an elastic structure, the structure will deform and this deformation can be
related to the magnitude of the pressure. It is most commonly used technique for fluids.
EQUIPMENTS TO BE USED
 U tube manometer
 Inclined Utube manometer

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Procedure :
*preparation of manometer pressure device
*preparation syringe
* push the syringe to generate pressure
*readers of different heights generated by
pressures
*pressure exploration due to height
* comparing the pressure between the pressure
gauge and pressure that I found .

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Calculation :
1- U-tube manometer(absolute )
P(mbar) H1(mm) H2(mm)
15 204 260
30 168 297
P=1500 N/M2
P=3000 N/M2
p= pgh
p=1000*9.81*(0.26m-0.204m)
= 549.36 N/M2
p=pgh
= 1000*9.81*(0.297m-0.168m)=1265.49 N/M2
2- U-tube manometer(vacuum )
P(mbar) H1(mm) H2(mm)
-15 287 174
-30 324 138
P=-1500 N/M2
P=-3000 N/M2
p= pgh
p=1000*9.81*(0.174m-0.287m)
= -1108.53 N/M2
p=pgh
= 1000*9.81*(0.138m-0.324m)=1824.66 N/M2

6. Fluid Lab
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3-inclind tube (absolute)
P(mbar) H1(mm) H2(mm)
15 198 298
30 155 339
P=1500 N/M2
P=3000 N/M2
p= pgh
p=1000*9.81*(0.298cos30-0.198)m
= 662.37 N/M2
p=pgh
= 1000*9.81*(0.339cos30-0.155)m=1442 N/M2

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Discussion :
A U-tube manometer is made up of a transparent tube having a small diameter
with a shape like letter “U”. This device indicates the difference between two
pressures (differential pressure), or between a single pressure and atmosphere
(gage pressure), when one side is open to atmosphere. When both ends of a U-
tube manometer are open, the liquid is at the same height in each leg. When
positive pressure is applied to one leg, the liquid is forced down in that leg and up
in the other. The difference in height, "h," which is the sum of the readings above
and below zero, indicates the pressure. The difference in pressure (PA- PB) is
determined by the negative product of specific weight of water and h4(water),
added to the product of specific weight of water and h3(water), added to the
product of specific weight of mercury and Δh (mercury), subtracted to the
product of specific weight of water and h2(water) and added to the product of
specific weight of water and h1(water).