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ABSTRACT
This project focuses on the design and fabrication of a non-frost non-frost refrigerating for cooling purpose. It operates on a temperature of 30C to 50C. The unit compresses of 1/10 hp compressor, condenser, evaporate and expansion valve which is the four major components that makes up refrigeration system. A thermometer was incorporated to read the temperature in the space as set by the thermostat. A galvanized stain less steel on 0.058m x 0.058m thick was used with the bending allowance of 0.0082m. refrigerant R600 which is ozone frently used. The unit can also be used for preservation of farm produce cake (guava, mango, avocado etc.) This system eliminate the constant freezing effect in refrigerating system which may cause consistent cleaning of the system.
CHAPTER ONE
1.1 REFRIGERATION
Refrigeration is the process of lowering the temperature in a given space and maintaining it for the purpose of chilling foods, preserving certain substances, or providing an atmosphere conducive to body comfort. Storage of perishable foods, pharmaceuticals or other items under refrigeration is commonly known as cold storage.
Refrigeration checks both bacterial growth and adverse chemical reactions that occur in normal atmosphere.
This cooling effect has been used on various scales from small space cooling to large industrial application (Liberty et al., 2003) several researches has been done on various forms of design of evaporative coolers.
The refrigerating system operates on vapour compression cycle, which the refrigerant is let into the evaporator in the liquid state and at near room temperature some of the refrigerant vapourizes under low pressure and the refrigerant evaporates, it removes heat from the evaporator and cabinet. The total amount of heat absorbed is the total latent heat of vaporization. The refrigerant vapour formed during evaporation, passes through the suction, line and decreases in pressure a little while the temperature increases. The compressor then takes the slightly superheat and convert it to a high temperature (sensible heat), high pressure vapour, as the required condensing pressure and temperature. At the condenser, the refrigerant loses its heat to the ambient temperature, water in forces draft air and changes to liquid state. The refrigerant then flows to the control, where the pressure reduced.
At this point some of the refrigerant will start to vaporize as flash gas. The rest refrigerant vapourizes inside the evaporator and cools the cabinet for another cycle.
The principle of refrigeration are based on the fact that heat and mechanical energy are mutually convertible, that is thermodynamics- the science that deals with the relationship between heat and mechanical action. The principle implies that heat is converted into work or work into heat through a mechanical process (Edwin P.A et al., 2017).
The first article refrigeration system begin in the mid 1750’s and developed in the early 1800s.
In 1834, the first working vapour compression refrigeration system was built and also the first commercial ice making machine was invented in 1854 and in 1913 refrigerator home use was invented.
In 1923, Frigidaire introduced the first self contained Unit, and the introduction of Freon in 1920s expanded the refrigerator market, newer refrigerators may include automatic defrosting chilled water and ice from a dispenser in the door.
1.2 Statement of Problem
The aim of every project is to solve a particular problem to help better our standard of living.
The most common uses of this mechanized refrigeration are the presentation of perishable foods more especially food stuffs, cooling of drinks etc. in sewing both functions and considering the area and situations of need such as resort centers, students hostels and single rooms apartments etc.
Hence the need arises more than ever to design the refrigerating system that will have the same cooling effect but will not ice (non-frost system) which will meet certain essential requirements such as cost effectiveness and portability.
1.3 Objectives of Study
The main object of this work is to design and construct a non-frost refrigerating system for domestic use, other specific objective include;
- To evaluate the performance of the system at reduction in length of the expander.
- To minimize regular cleaning of the refrigerating system which could be caused by icing.
- To evaluate the validity of some perishable agriculture produce stored in the system.
1.4 Justification
This project is a design and construction of a non-frost refrigerating system, which is a refrigerating system that will only cool but will not ice a frost. There is a need for this due to storage of drinks and also farm produce (perishable fruits) some methods of preservation of raw and processed fruits/vegetables will be preferred with this system because the cooling effect will preserved them more than when it is frosting, it also has its disadvantage after some period of time. This process has been found to be efficient in some industry and factories who only prefer some of their drinks to be cooled but not iced (Dzivama 2017).
1.5 Scope of the Project
This work will mainly focus on design and construction on a non-frost refrigerating system for domestic purpose, which is based on cooling effect but no icing effect.
1.6 Limitation of Study
- It does not form ice but only cools and preserve
- They are not effective in humid region