DESIGN AND CONSTRUCTION OF A REFRIGERATING UNIT

ABSTRACT

The design and construction of s refrigerating unit is handled from the knowledge of the working principles of laws of thermodynamics.

The size of the containing vessel i.e the case as established to be of 45cm by 32 cm in dimension. The Angle iron mild steel to used in the fabrication and welding. The box case of two layers are fabricated. Plastic (cooler) box is then  placed inside the upper part with the other parts of the refrigerator were brought in. they were all fixed onto a wooden base with all the connections (electrical) made.

The capacity of the refrigerator is based on the workdone by the compressor which is O.I hp in specification. The size of the components used are

i.    Condenser: The size is 0.1hp and it is a plate type condenser with extended surface.

ii.    Compressor: The size is 0.1hp (75 watts)

iii.  Copper wire: it is of 0.5cm in diameter and the total copper wire length is about 600cm (1½ roll)

The introduction of cooling fluid and filling of the compressor enabled the compressor to start functioning when connected to electricity using a 13 AMP rated socket

The interior of the plastic box is lined with dominium box with tubes arranged in convolution around it. This world effectively and cooled the water dropped into it. It compares favorably with the ones in the market.

CHAPTER ONE

1.0   INTRODUCTION

Refrigeration is the process of lowering the temperature of a substance below that of its surroundin

Refrigeration is the practical application of the first and second law thermodynamics. Comprehensive understanding of the basic principles of thermodynamics is crucial for full understanding of basic operation of refrigerator. The first law states that the energy can neither be created nor destroyed. If energy of 2.5J appears in one forms it appears in another without a corresponding decrease of energy on the other form. The second law states that no system can receive heat at a given temperature and reject it at a higher temperature without receiving work from the surrounding heat always flow from Warner to cooler body. Through consideration of these laws, the ideal refrigeration cycle are considered. The carnot cycle is reversible and consist of adiabatic compression witherma rejection of heat, adiabatic expansion and wothermal addition of heatl the carnot cycle is unattainable ideal which serves as a standard of comparison and it provides a convenient guide to the temperature that should be maintained to achieved effectiveness. The efficiency or coefficient of performance (C.O.P.) of a carnot cycle depends on the temperature at which heat is added and rejected.

Therefore,

C.O.P =           T1

T2 – T1

Where T1 = Evaporation temperature

T2 = Conducting temperature

In actual refrigeration there will be issues causing C.O.P to be less than that for ideal cycle. The basic methods of refrigeration like the mechanical refrigeration ejector (steam jet) refrigeration absorption refrigeration uses similar process for obtaining refrigeration effect. That is evaporation in the evaporator, condensation in the condenser, the main difference is in the way used refrigeration being done. The most compression. The cycle efficiency can be ignored in a number of ways.

1.  Multistage system: When evaporation and condensing temperature (pressure) difference is large, it is prudent to separate compression into two stages. The use of multistage system open up the opportunity to use flash gas removal and inter cooling as a measure to improve performance of the system

2.    Cascade system: This appears in situation where the evaporating temperature is very low (below 600c). the refrigerant is used to achieve the cooling. The liquid with low boiling points are used as refrigerants.

1.1       SCOPE OFD THE PROJECT

The scope of this project is mainly concerned with the design and construction of a refrigerating unit that has a very performance level and with the cost of fabrication lower than that of existing prototype

A good refrigerator is one that has all the basic components of compressor, condensers, fan motor, copper tubes and other. This project must apply all the principles of refrigeration.

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