DESIGN AND FABRICATION OF A DEEP FREEZER
This project is on the design and fabrication of deep freezer for the preservation of items/products and making the items to cool. The project is able to develop a simple efficient economical and environmental friendly refrigeration system (A freezer) towards better technological advancement in Nigeria. This project modifies the existing refrigeration system with the use of R-600a which is ozone friendly, and non-contaminant like previous refrigerant of the hydrofluoric-carbon, HFC and CFC like R-12, and R22 which has been phased out according tothe general convection at Britain in 1996. The cooling load obtained was 10682KW, and co-efficient of performance be minimized. The material used were mild steel and the inner pipe of the cabinet i.e. evaporator in order to minimize corrosion. For the better improvement of this work, low power consumption of the compressor refrigeration was used so as to maintain the rate of cooling and freezing of large items/products. And the outer dimensions are: length-1245mm, breadth-895mm-0. 895m, Height-906mm-0.96m and the inner dimensions are Iength-1225mm-1.225m; Breadth-895mm-0.895m, Height-886mm- 0.886m.
TABLE OF CONTENTS
Title page i
Table of content vi
CHAPTER ONE: REFRIGERATION
1.0 Introduction 1
1.1 Literature Review 2
1.2 General Definition and Development 3
1.3 Purpose and Scope of Refrigerator 4
1.4 Objectives of the Project 7
CHAPTER TWO: TYPES OF REFRIGERATOR SYSTEM
2.0 Types of Refrigerator System 8
2.1 The Vapor Compression Refrigeration System 8
2.2 The Vapor Absorption Refrigeration System 9
CHAPTER THREE: DESCRIPTION OF THE COMPONENTS PARTS
3.0 Description of the Components Parts 13
3.1 Compressor 13
3.2 The Condenser 16
3.3 The Evaporator 17
3.4 Pressure Gauges and Thermometers 19
3.5 Strainer/Drier 19
3.6 The Capillary Tube 20
CHAPTER FOUR: DESIGN CRITERIA, CALCULATION AND ELECTION OF EQUIPMENT
4.0 Design Criteria, Calculation and Selection of Equipment 21
4.1 The Evaporator Cabinet 21
4.2 Design Condition 22
4.3 Evaporator for Cabinet Casing 23
4.4 Conducted Heat 27
4.5 Refrigerant Piping Design 28
4.6 Calculations of Component Parts 32
4.7 Refrigerator Load Estimation 40
4.8 Refrigerant Used 41
4.9 Determination of the Flow Rate 47
4.10 Heat Balance for the System 48
4.11 Co-efficient of Performance 50
CHAPTER FIVE: FABRICATION DETAILS
5.1 The External Cabinet and Material Select 53
5.2 Insulation 53
5.3 Compressor Base 55
5.4 Condenser 55
5.5 Assembly of Part 55
5.6 Lubricants in Refrigeration System 56
5.7 Trouble Shooting in Domestic Refrigerator 57
5.8 Bill of Engineering Materials and Evaluation (BEME) 59
CHAPTER SIX: CONCLUSION AND RECOMMENDATION
6.0 Conclusion 60
6.1 Recommendation 60
The ice cream being sold at the corner stores, the frozen vegetable for dinner, the refreshing water for drinking at the office, water cooler are all dependent on the science of refrigeration. Refrigeration in its specialized forms in a comparative modern development which has been in practice for generations, and its application in controlling environmental condition has made possible some outer space programs and many other scientific and commercial activities as it can be obtained in our houses and on the farm which is considered as an example of a natural refrigeration techniques, the porous clay jugs used in hot desert countries for cooling water, the ice box, for food preservation etc. (Raymond, C.G. (1973).
This write up presents the principle of mechanical refrigeration in vapor compression refrigeration system and it application which gives a clear understanding about the design and operation of the unit.
1.1 LITERATURE REVIEW
Refrigeration is branch of engineering that is concerned with the science of producing and maintaining temperature below that of the surrounding atmosphere [Raymond, C.G. (1973)]. It also the process of removing heat from the substance.
Before the advent of mechanical refrigeration, water was kept cool by storing in semi-porous pots, so that the water could seep through and evaporate. The evaporation carried away heat and cooled the water [Raymond, C.G. (1 973)].
The first development took place in 1834 when Perkins proposed a hand operated compressor working machine. In 1851 came Gorries and in 1856 Lind developed a machine working on ammonia [Andrew, D. & Alfred, (1970)]. The development was considered quickened in the forties when Dupent put in the market, a family of new working substances, the floro chloro derivate of methane,1 ethane etc. under the name of ferons; then followed the liquefaction of other permanent gases included helium in 1908. [Andrew, D. & Alfred, F.B. (1970)].
In 1926, Ginque and Diebye independently proposed adiabatic demagnetization of a paramagnetic salt. In 19th century application of mechanical refrigeration in fields other than ice making including direct cooling and freezing of perishables foods, air conditioning for industry and human comfort [[Andrew, D. & Alfred, F. B. (1970)].
1.2 GENERAL DEFINITION AND DEVELOPMENT
Refrigeration may be defined as the process of removing heat from a substance. The American society of Engineers defines refrigeration as “the science of producing and maintaining temperature below that of the surrounding atmosphere”. This implies the development of temperature differential rather than the establishment of a given temperature level.
Therefore refrigeration is accomplished by establishing temperatures differentials and evaporation of liquids or combination of both methods for removing heat from a substances in a refrigeration i.e. heat is put into the working substance at lower pressure and temperature and provide the latent heat to make it boil and change to vapor. The vapor is then compressed to a high pressure and temperature at which the superheated gas can be removed and the fluid is turn to liquid. The total cooling effect will be the heat transferred to the working fluid in the evaporator [Raymond, C. G. (1973)].
In any refrigeration process, three basic factors are involved which are: Heat change, pressure control and liquid gas relationship, therefore a working system will require a connection between the condenser and the inlet to the evaporator to complete the circuit.
1.3 PURPOSE AND SCOPE OF REFRIGERATOR PROJECT
The purpose of refrigerator deals with the use of refrigerator which is in three forms.
i. To produce the temperature of a substance (Act of cooling).
ii. To change a substance from one state to another (as water to ice)
iii. To maintain substance in a desired temperature state (food preservation or ice storage) [Raymond, C. C. 1973].
All the above purpose is personal comfort in both temperature and hot climatic regions. It importance to the society can also be grouped under the following sub headings:
1. DOMESTIC: Refrigerators are commonly used in the house for domestic purpose. They are usually in all sizes having a compressor rating between (1/2) half and (1) one-horse power and are hermetically sealed type. They are commonly employed for cooling drinks and as food preservation [Andrew, D.
& Alfred, F. B, (1970)].
2. COMMERCIAL: Commercial refrigerators is concerned with designing, installation and maintenance of refrigeration fixture of the type used in retail store, restaurant, hotels and institution for storing, processing and dispensing of perishable goods [Andrew & Alfred, F. B. (1970)].
3. INDUSTRIAL: Industrial refrigerator are larger in size than commercial application and have the distinguishable features requiring an attendant on duty, usually of licensed operating engineer Example are ice plant, large food packaging plant, breweries, ceramics and in industrial plant such as oil refineries, chemical plant and rubber plant [Andrew, D. & Alfred, F. B. (1970)].
4. MARINE AND TRANSPORTATION: Refrigeration are needed for fishing boats and for marine vessels transporting perishable goods This is also applied in modern passenger train and trunks for carrying chilled fish, meat and other refrigerated fixture through a long distance [Raymond, C. 0.(1973)].
5. AIR CONDITION: It deals with the control of temperatures and humidity of the air, moisture filtering and cleaning of air within some designated areaor space. They are of two types, the comfort air application or industrial air- conditioning, it could be formed in the control of moisture content of hygroscopic material governing the rate of chemical and biochemical reaction, limiting variation in the size of precision and manufactures articles due to thermal expansion and contraction, filtered is often essential to trouble free the operation and to give production of good product. [Raymond. C. O. (1973)].
6. HOSPITAL: Refrigerators are used in hospital for preservation of bones, blood tissue and some drugs that are kept under a particular temperature; it also play an important role in the act of keeping dead Bodies in mortuaries from being decayed [Raymond, C. G. 1973)].
1.4 OBJECTIVES OF THE PROJECT
This project is to educate students of engineering and refrigeration technology lovers on how to achieve maximum cooling during refrigeration by increasing the coefficient of performance (COP) [Andrew, D. & Alfred, F.B. (1970)].
This project will help in the aspect of teaching the users of refrigerator the necessity of taking good care of their refrigerator, the danger of using sharp point object which could eventually damaged the evaporator..