CHAPTER ONE

1.0     INTRODUCTION

A mobile refrigerator is not a different refrigerator than a refrigerator that is portable (ie it can be moved fro one place to another with little application of force).

Here, the mechanical refrigeration has to do with the production of a machine that controls a temperature lower than atmospheric temperature.  This implies that it is t he process of removing heat  at a low temperature level and rejecting it at a relatively higher temperature level.

By its nature, heat flows from a body at a higher temperature to anot her at a lower temperature but in the reverse case, it requires external energy to be accomplished. T he carrier substance used to carry heat is called a refrigerant.  Therefore refrigerator is the reversed heat engine cycle.

Refrigeration is accomplished by various methods, such as the vapour compression system, absorption system, and steam jet refrigeration cycle.  In this project only vapour compression system of refrigeration shall be discussed as it was the method adopted to accomplished the refrigeration.

Refrigeration contributes to the raising of living standard of people of all classes and land.  Although refrigeration is primarily an of thermodynamics, but advances made refrigerant in recent years to grow into so many phrase where we need technicians, craft persons, engineers, scientists, and others from phases of engineering pool skills and knowledge in the design, manufacturer application and operation of the refrigeration.  Complete knowledge of thermodynamics and properties of refrigerants must be known before the complete cycle analysis can be made.

The application of the refrigeration principle is limitless.  The most common used and ones that is readily recognized is the preservation of food and chilling of our drinks and water during the time we are feeling hot and need our body to be chilled.

1.1     PURPOSE OF CONSTRUCTION

          The main objectives of the this project is to achieve the following purpose viz:

1.      To construct and fabricate a portable domestic cooling equipment that would be easy to be moved to any convenient position.

2.      To construct a cooling/freezing system that is efficient with little or no complexity in maintenance.

3.      To construct cooling system that will be mobile, economic and cost effective that even a common man can afford.

4.      To produce a machine that will make life easier and more comfortable to live, even in a hot environment, and season.

5.      To construct a portable cooling system equipment with a reduced weight.

1.2     IMPORTANCE AND SPECIFICATION OF PROJECT

The importance attached to this construct is the accomplishment    of a fast freezing system without breaking of bottles at very low temperature and without adverse effects on the food tissues, the flavour, freshness and natural nutrients of food materials.  The construction intention is based on reduced weight and cost, longer life span, fast freezing techniques, compactness, portability and so on, while constructing this project we put into consideration the Nigeria factor and possibility of expanding and marketability and its adverse effects on our environment, that is why we used refrigerant that has no effect on our ozone layer.

While taking the specification on the size we put into consideration the item that are to be cooled or preserved.  Also the cabinet dimensions and compressor capacity were put into consideration as well.

The essential design parameters for the mobile refrigerator are as follows:

I.       Compressor

II.    Capillary tube

III. Condenser

IV. Evaporator

V.    Thermostat

VI. Refrigerant

VII.                      Rubber seal

VIII.                   Drier

IX. Relay and overload

X.    Rollers

XI. Lagging materials

XII.                      Lubricating oil

XIII.                   Mild steel metal sheet

XIV.                   Aluminum sheet

XV.                      Valve

1.3     SCOPE AND LIMITATION

Refrigeration can be divided into three main categories namely:

I.       Industrial refrigeration

II.    Commercial refrigeration

III. Domestic refrigeration

The design “mobile Refrigerator” as it’s name entails is for domestic application and to some extent for commercial purpose due to its fast freezing nature and mobility.

Well the limitation of this mobile cooling system is basically on its specification in terms of size, capacity and area of need in terms of power source.  Based on the specification, the equipment is not congruent for industrial use, where large refrigerator unit are more ideal and readily available.

1.4     STATEMENT OF PROBLEMS

The use of low temperature refrigeration to obtain expansion fits has substituted shrunk fitting of metal parts, in the chilling of aluminum rivets to control age hardening, the stimulation of straphere conditions in the laboratory for the testing of all types of air craft equipment, including the engine themselves requires refrigeration at  - 670F, in the process industries refrigeration is used to carry out such operation a s the separation of crystals from solutions.

Application of refrigeration in the medical profession is increasing daily, not only in the preservation of certain products, but also in the actual treatment of some physical ailments.  The use of cold “anesthesia” has shown great promise in the field of surgery.  The manufacture of penicillin requires refrigeration and removal of moisture under high vacuum.  The same process is required in the drying of blood plasma, and the preservation of blood which requires refrigeration before the dry is accomplished.

In the refrigerated food industry, developments are occurring so rapidly that it is difficult  to keep abreast of them.  In case application of domestic refrigerators have been supplemented by the entire new field of domestic low – temperature cabinets for the preparation and storage of frozen foods, both inc cooked and pre cooked.  Lower plants for the storage of frozen food are becoming common thing both in our rural and urban areas.

The movement of our foodstuff has been a matter of concern over years, but with the new development in the refrigeration of ships, rail road, cars and trucks.  These are but a few of the widespread applications of refrigeration.  In serving some of the function and considering the area and situation of need such as resort centers, picnic, school etc.  Hence the need arises more than even prior to design of mobile cooling system of acceptable standard that will meet certain essential requirement such as portability and cost effectiveness.