ABSTRACT
Mechanical
Engineering Department of the named institute has many has non operational
machines sequel to the fact, maintenance was poorly executed which resulted to
the breakdown of this refrigerator.
Quality and effectiveness of
machine maintenance were well observed.
Also, a minimized cost of maintenance and a highly successful repair was
adopted.
In otherwords, during the repair
and rehabilitation of this refrigerator appropriate tools, cost and quality of
materials were well considered.
INTRODUCTION
Refrigeration
is the process, which deals with the process of reducing and maintain the
temperature of a material or space below the temperature of the
surroundings. Refrigerator is an electro
mechanical appliance, which carry out the refrigeration principle.
In otherwords, a refrigerator
absorbs heat from a low temperature region.
Consequently, thus he at flows are transmitted through a medium or mode
conduction, convention and radiation transmit heat. Conduction and convection art extensively
adopted in refrigeration.
Refrigerators contain some
components, which transmit the mode of heat flow. They are compressors, evaporators, condenser,
and expansion valve etc. These
components after some constant usage are required to be maintained. Maintenance is generally defined as the up
keep repair, renewal and replacement of worn, damage or absolute parts of a
machinery, equipment or building. These
can be corrective, preventive or breakdown maintenance. Observing the steps in tracing the faults
associated with each component and the necessary replacement in this case
carried out maintenance or repair was carried out.
These activities were carried out
using the instrument for the refrigeration repair such as pinch off tools,
ratchet, manifold guage, and thermometer, the application of halide lease
detector.
In this write up, the application
and uses of refrigerator was discovered, refrigerants and their properties,
determination of co-efficient of performance (COP) and refrigerator effect, as
well as sequence operation and cost analysis.
Summarily, this test contains all
you need to know about, refrigeration and its principle, application and uses,
it maintenance, determination of the COP and refrigeration effect, as well as
sequence of operation and cot analysis.
TABLE
OF CONTENTS
Title
page
Release
page
Letter
of transmittal
Approval
page
Acknowledgement
Dedication
Abstract
Literature
review
Introduction
Table
of contents
CHAPTER ONE
Refrigeration
Refrigerant
Refrigerator
CHAPTER TWO
COMPONENT
PARTS OF A REFRIGERATOR
CHAPTER THREE
Maintenance
Repairs
and rehabilitation
Step
taken towards ensuring adequate maintenance of the refrigerator
CHAPTER FOUR
Tools
And Instrument Used In Maintenance Of Refrigerator
CHAPTER FIVE
Application
And Uses Of A Refrigerator
CHAPTER SIX
Determination
Of Cop And Refrigeration Effect
CHAPTER SEVEN
Cost
evaluation
Conclusion
Bibliography
CHAPTER
ONE
REFRIGERATION
Refrigeration
is defined as a process of removing heat from a substance or space in other to
make it cooler. More so, it is the
branch of science which deals with the process of reducing and maintaining the
temperature of the surrounding.
Generally, for a space to be
cooler, it must lose heat to another substance.
Also for a space or material to get hotter, it must absorb heat from
another substance. Thus, heat is the
characteristic agent of heating and cooling.
Consequently, for heat to flow, there must be a medium or mode for the
transmission. This always follows from
high temperature region to low temperature region/bodies.
The modes of heat transmission
are conduction, convection and radiation.
Conduction and convection are extensively involved in domestic
refrigeration.
In
refrigeration process, there is always a body employed as the heat
absorber or the cooling agent which may
be near to the material or space being cooled or space being cooled or in
direct contact with the material being cooled depending on the required final
effect such a cooling agent is known as the Refrigerant. The refrigerant circulates around the
evaporating and condensing regions. In
other to maintain a constant refrigeration process it does it work by
evaporating and condensing. When it
loses the absorbed heat to return to its original liquid or solid rate, as the
case may be classified a s sensible heat or latent heat, (depending on the
physical effect on the refrigerants.
Generally, when a mass or body absorbs heat the following physical
changes takes place.
1.
The
mass expands or increases in physical dimensions as the molecules resonate
within a wider range
2.
The
temperature increase (as the molecules gain more internal lunatic energy)
3.
There
is a change in phase (as the mass changes from solid to liquid and consequently
to gas and vice versa)
4.
The
specific density decreases (as the mass remain constant while the volume
increase) etc.
All
these result to the refrigerant evaporating into the surrounding
space/atmosphere and needs to be physically re-cycled to the original condition
for another turn of refrigeration. Over
and over again, the processes are repeated and more cooling achieved. Moreover, the sensible heat leads to the
increase in the temperature of the refrigerant from one phase to another phase
(solid – liquid – gas). A refrigeration
cycle is said to have been completed when this refrigerant has undertaken all
its metamorphic circulation from the compressor, round, and back to the compressor
again.
Another area worthy of
consideration in refrigeration is the pressure effect. It has a linear and positive relationship
with temperature, which is the basic property of the transmission. Adding pressure to the body induces internal
stress on the molecular structure of the body.
Pressure can be used to increase the heat capacity of a body, thus,
increase in the atmospheric pressure of a substance brings about a relative
increase in the boiling point of that substance. Also, sudden expansion or a compressed gas
brings about an effective cooling and this explains the reasons why refrigerant
gases are sealed and circulated under pressure. On the other hand, a reduction
in the atmospheric pressure of a substance brings about a comparative decrease in
the boiling point of that substance, in all, pressure increase and decrease of
a particular substance causes temperature increase and decrease respectively of
that substance.
Never the less, the whole of the
refrigeration conditions explained above in abstract in the natural
realms. Heat does not flow from a cold
region, as in the refrigeration process without work done against the natural
principle. Hence, energy is required,
which is artificially produced and at this we now talk of refrigeration.
THE REFRIGERATOR
A
refrigerator is an electro mechanical appliance, which is used in maintaining
the temperature of substance as required by the user, or it is an electro
mechanical appliance used in carrying on artificial cooling. It operates with the principle of reversed
carnet cycle. In other words, heat is
absorbed from a low temperature region and rejected to a high temperature
region. The temperature at which heat is
absorbed are kept at constant.
The
energy for the pumping of the refrigerant
round the refrigeration cycle comes from the compressor (that of the
refrigerator). It makes use of other
mechanical and electric al components.
The torque for driving the crankshaft and consequently the piston is
produced by an electric motor (it makes use of magnetic effects of
current). Similarly, the pumping effect
of the piston creates the high pressure which induces to the
refrigeration. This thus, sets in motion
the refrigerants, which after some physical metamorphosis returns to the former
state ready for another cycle.
In the refrigerator, the condenser performs a
function similar to that of the radiator in an automobile. It is the cooling coil for the hot
refrigerants gas. In the condenser, the
refrigerant is condensed and expelled to the surrounding atmosphere, the
metering device expands the gas as another pipe passes through the capillary
tube and suddenly expands into another pipe of
larger cross section, the evaporator consist of convolutions of a copper
tubing which is where the actual cooling action of the refrigerator takes
place.
However,
a hot of insulation is done to
isolate t he refrigeration space from the surrounding environment and its
effects. This is achieved by the
following measures.
i. The body was made up or lagged with poor heat conductor.
ii. The inside and the outside are brightly
coloured to effect light and heat reflection
iii. The condenser tubing is positioned
externally at the back of the refrigerator and a very poor heat conducting
materials like fibre glass.
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