ABSTRACT
The aim of this project was to
construct shell and tube heat exchanger with fixed boundless. A heat exchanger
that would cool 5 x 5 x 10 – 3 kg/s of steam at a calculated heat
load of 152 – 395/S was fabricated. The steam is to reach the heat exchanger
from a distillation column at a temperature of 300k. The specification of the layout as well as the detailed mechanical
design were assumed and also calculated.
It is established that a horizontal
heat exchanger with cold water at the shall side and the treated steam at the
tube side is adequate for this operation, with the aim of cooling the steam
from the distillation column.
The available area obtained from
calculation is 1.0m2 and also the overall heat transfer coefficient
obtained is 4.10W/M2k. it is also seen that the heat exchanger is
satisfactory and consists of five copper tubes of inside diameter 90mm and
5920mm length. The shell inside diameter 810mm and 5.770mm length. The tube and
shell heat exchanger has a total length of 5820mm.
The material of construction for the
shell side is stainless steel while copper tubes were used for the tubes inside.
The total cost of the heat exchanger
was N12,000.
TABLE
OF CONTENTS
Title
Page
Approval
page
Letter
of transmitted
Dedication
Acknowledgements
Abstract
Table
of contents
CHAPTER ONE
1.1
Introduction
CHAPTER TWO
2.0
Literature
Review
2.1 General Design of Heat Exchanger
2.2
Tubular
Heat Exchanger
2.3
Design
Description of the Major Components
2.4
Tubes
2.5
Tube
Bundles
2.6
Shells
2.7
Baffle
2.8
Tie
Road Spacers
2.9
Pass
Partition Plates
CHAPTER THREE
3.0
Fabrication
Procedures
3.1 Dimensioning and Marking Out
3.2
Cutting
3.3
Folding
or Rolling
3.4
Drilling
operation
3.5
Assembling
Process
3.6
Welding
Operation
3.7
Filling
3.8
Dimensions
and Parameters Derived
3.9
From
the Fabrication Units
CHAPTER FOUR
4.0
Costing
CHAPTER FIVE
5.0
Discussion
CHAPTER SIX
6.0 Conclusion
6.1
Recommendations
CHAPTER SEVEN
7.0 Notation and Nomenclature
References
Appendix
Physical Properties of Water
Calculation
of the Head Load
CHAPTER
ONE
INTRODUCTION
In large industrial processes, it
is necessary to transfer heat between the system and its surrounding and the
device whose primary objective to do it efficiently and effectively is the heat
exchanger.
Therefore heat transfer is defined as
the rate of exchange of heat between one body (hot) and another cold.
The most important aim in the chemical
engineering sector of any plant is to control the flow of thermal energy
between two terminals. It there existing temperature gradient of change.
In industrial process, the heat
exchange is a very important unit in all the processing industries that their
design has been highly developed. Designers of heat exchanger must be
constantly aware of the difference between the idealized conditions for and
under which basic knowledge was obtained and the real conditions of the
mechanical expressions of their design and it’s environment.
The design must satisfy process
operational requirement such as availability and maintainability.
Heat transfer or thermo-kinetics is
another chapter of the theoretical fundamentals of heat engineering dealing
with the processes of heat propagation. In nature and engineering, the most
diverce process of heat propagation are observed and also heat flow from bodies
(or their section) of a lower temperature. During the process of heat transfer,
from one body to another heat flow continues till their temperature became
equal be come to equilibrium state of temperature.
MODES OF HEAT TRANSFER
Heat is transferred by conduction,
convection and thermal radiation. In practice, heat is usually transmitted by
two or all the three modes of heat transfer concurrently.
CONDUCTION
Heat conduction of simply conduction
is the transfer of heat by a direct contact between the elementary particles of
a body, Viz molecules, atoms, free electrons, when the bodies involved are at
rest.
Pure conduction takes place in opaque
or non transpired solid.
In goses, conduction occurs due to
random motion of the molecules (the diffuse from high concentration region to
lower region. In this made of heat transfer, it is very common with metals and
thus call for high thermal conductivity. Also the heat transfer per unit area
is proportional to normal temperature gradient given as:
Q = dt = (1)
A dx
Fourier
postulated an expression for heat transferred by conduction called fouriers law
gives by:
Q = KA dt = (2)
Dx
Where
Q rate of flow of heat J/S or welts
K = Fourier’s
constant
A = Area
of heat transfer perpendicular to the direction of heat flow (M2).
dt/dx
temperature gradient (0C or K
).
CONVECTION
This involves the transfer of heat
from one body to another by the mobile particles of liquid, gas or coarse
solids during their relative motion in space. Convection heat transfer can be
illustrated by the transfer of heat by heated air from a stove to the upper
layers of the room air. Convection consist of forced and natural convection.
Forced convection is widely used in chemical processing industries. The
expression below shows heat transfer by convection.
Q = KA (Ti – To) = (3)
= hA (Ti – To) = (4)
where h k/x
Q = heat
transfer rate J/S or welts
K = Proportionality
constant
X = Distance
over which heat is transferred (m)
A = Area
(M2)
Ti and
To = Temperature
at different point (0C or K)
h = Convection
heat transfer co-efficient (w/m2k)
RADIATION
This is a process of heat
transferred by electromagnetic waves through a machines which is transparent to
thermal radiation. During this process, a fraction of the thermal energy of a
hot body is converted into radiant energy which, when encountering an opaque
body again turns partly into heat.
From the second law of thermodynamics,
STEFANBOLTZ MANU prop
Proposed
that heat is directly proportional to the fourth power of the temperature and
the surface area.
Thus
given as:
Q = såAT – 4 = (5)
Where s = Stefan – Boltman constant
Ã¥ = Emissivity
surface
T = Absolute
temperature (0C or K)
A = Area
of heat transfer (M2)
Q = Heat
transfer rate J/S or welt
HEAT TRANSFER EQUIPMENT
There are various types of heat
exchange equipment generally defined by the function it performs in a chemical
industry. Generally, heat exchange is the equipment whose primary objective is
to transfer heat energy between two fluids. These equipment are classified into
three categories mainly:-
(a) Regenerators
(b) Open type heat exchangers and
(c) Closed type bread exchanger or
recuperations
a. REGENERATORS
These are heat exchangers in
which the hot and cold fluid flow through the same space alternatively with a
little physical mixing as possible occurring between the two streams. The
amount of heat transferred depends on the fluid and flow properties of the
fluid streams as well as the geometry and thermal properties of the surface.
b. OPEN TYPE HEAT EXCHANGERS
These are devices where by fluid
stream flow into an open chamber and there the complete mixing occurs. Hot and
cold fluid enter the exchanger separately and will at the other end leaves as
single fluid stream.
c. RECUPERATORS OR CLOSED TYPE HEAT
EXCHANGERS
They are those in which the heat transfer occurs
between the two fluid stream that do not physical contact each other. The fluid
streams involved are separated from one another by a tube wall or a pipe. Heat
transfer occurs by convection from the hot fluid to the solid surface, by
conduction through the solid surface and then by convection through solid
surface to the cooler fluid.
Another classification is based on
relative flow direction of the two fluid streams. They include:-
i.
Parallel Flow: When the fluid stream flow in
the same direction.
ii.
Counter Current Flow: The fluid streams flow in
opposite direction.
iii.
Cross Flow: If the fluid stream flow at
right angle to one another.
The
other classification is based on tube construction:-
i.
Double
– pipe heat exchanger
ii.
Shell
and tube heat exchanger
iii.
Extended
– surface exchangers
iv.
Spiral
plate exchanger
v.
Graphic
block heat exchangers
vi.
Scrap
surface exchanger.
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