Description
ABSTRACT
Conventional refrigeration systems have been majorly exploited since the 20th century. This has eventually caused major problems in the use and disposal of chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs); ozone layer depletion being the worst case scenario. However, efforts have been directed towards the development of non-conventional types of refrigeration technology such as thermoelectric refrigeration, magnetic refrigeration and thermoacoustic refrigeration which has proved to be eco-friendly, cost-effective and efficient in operation. The present work is on the design and construction the of a portable thermoelectric refrigerators with a digital temperature display. As a result, there will be less power consumption and totally eco-friendly refrigeration compared to conventional refrigeration with the same refrigerating effect.
TABLE OF CONTENT
COVER PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
TABLE OF CONTENT
CHAPTER ONE
- INTRODUCTION
- BACKGROUND OF THE STUDY
- STATEMENT OF THE PROBLEM
- AIM AND OBJECTIVES OF THE STUDY
- PURPOSE OF THE WORK
- SCOPE AND LIMITATION OF THE STUDY
- APPLICATION OF THE STUDY
- SIGNIFICANCE OF THE STUDY
- METHODOLOGY
- PROJECT ORGANIZATION
CHAPTER TWO
2.0 LITERATURE REVIEW
2.1 REVIEW OF REFRIGERATION
2.2 HISTORICAL BACKGROUND OF THE WORK
2.3 THERMOELECTRIC COOLING SYSTEM
2.4 REVIEW OF RELATED STUDIES
2.5 THERMOELECTRIC MATERIALS
2.6 ADVANTAGES AND DISADVANTAGES OF PELTIER EFFECT
CHAPTER THREE
3.0 METHODOLOGY
3.1 COMPONENTS OF THE THERMOELECTRIC REFRIGERATOR
3.2 SCHEMATIC DIAGRAM OF THE REFRIGERATOR UNIT
3.3 WORKING PRINCIPLE COOLING EFFECT
3.4 DIGITAL DISPLAY CIRCUIT
3.6 CIRCUIT DESCRIPTION
3.7 PROGRAM CODE
CHAPTER FOUR
4.1 CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
4.2 ASSEMBLING OF SECTIONS
4.3 TESTING OF SYSTEM AND RESULT
4.4 ADVANTAGES OF THERMOELECTRIC COOLING
4.5 LIMITATIONS OF THERMOELECTRIC REFRIGERATOR
4.6 THERMOELECTRIC COOLING VERSUS TRADITIONAL REFRIGERATION
CHAPTER FIVE
5.1 CONCLUSION
5.2 RECOMMENDATION
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Energy crisis, ozone depletion, and global warming have become more and more serious with the social development. The amount of energy consumed by air conditioners, refrigerators, and water heaters is increasing rapidly, and occupies about 30% of the total power consumption [Jahangeer et al, 2011]. Electricity consumption for refrigerators has been estimated around 45% for residential and commercial buildings [Kalkan et al, 2012]. Because of the rapid growth in world population and economy, the total world energy consumption is projected to increase by about 71% from 2003 to 2030 [Wimolsiri et al, 2004]. In Nigeria, the rate of electricity consumption growth more than 7% annually and would need to double its current generation capacity by 2020. Furthermore, primary energy requirement in Nigeria increases by 2.6% every year [Elsafty et al, 2002]. So for this reason a low energy consuming refrigerator was built – thermoelectric refrigerator. The most widely used refrigerators are employ the conventional vapor compression cycle due to its high COP. These systems use a liquefiable vapor as the refrigerant and require mechanical power for driving the compressor, which is usually provided electrically. However, these systems are now. less attractive because the chlorofluorocarbons (CFCs) refrigerants have a high ozone depletion potential (ODP), high global warming potential (GWP), high consumption of electrical energy, which is usually supplied by fossil fuel combustion, producing greenhouse gases and other pollutants [Abu-Zour et al, 2007]. In addition, there are several areas where grid electricity is not available at the moment and is unlikely to be available in the next few decades due to the huge financial outlays involved. These include These include villages, rural areas and remote locations in developing countries. Hence, direct current powered cooling systems such as thermoelectric cooling systems consider interesting in that it can be powered with 12v battery or with solar energy from solar panel. In these systems, can be achieved using thermoelectric effect, which refrigeration converts electrical energy supplied by 12v supply into a temperature gradient. Thermoelectric cooling influenced predominantly by the Peltier effect, James Peltier discovered in 1834. Peltier effect occurs when a direct current (DC) is passed between two electrically dissimilar materials, either heating or cooling occurs at the junction, depending on the direction of the electric current [Rowe, 2006]. The conversion of electricity into heat is called thermoelectric cooling, whereas the opposite effect, that is, the conversion of heat into electricity, is called thermoelectric generation. Thermoelectric cooling systems have no mechanical moving parts and do not employ working fluids, which transfer heat from the cold side of the modules to the hot side with consumption of electricity [Tie et al, 2013]. Due to the advantages such as high reliability, low weight, and flexibility in packaging and integration, thermoelectric cooling systems have been widely used in military, aerospace, instrument, and industrial products [Riffat et al, 2013] Thermoelectric cooling systems can be powered directly with battery or by a photovoltaic (PV) without the help of AC/DC inverter, which greatly reduces the costs. However, the main aim of this study is to build a 12v thermoelectric refrigerator.
1.2 PROBLEM STATEMENT
In the current scenario, high voltage refrigerator is very efficient and reliable but it has some negatives. It has been observed during the last two decades that the O3 layer is slowly destroyed because of the refrigerant (CFC and HFC) used for the refrigeration and air- conditioning purposes. The common refrigerant used is HFC’s which are leaked and slowly ascend into the atmosphere. When they reach to O3 layer they act on O3 molecules and the layer of O3 is destroyed. A single molecule of HFC can destroy thousands of O3 molecules and that’s why it has created a threat for the not only to maintain earth eco system stable but also to of existence of earth, and also, high voltage refrigerator consumes much power. These problems led to the use of thermoelectric units which could be powered from a 12v dc used in cooling technologies such as a refrigerator.
1.3 AIM AND OBJECTIVES OF THE STUDY
The main aim of this study is to build a battery powered (12v) thermoelectric refrigerator with digital temperature display. The objectives are:
- To build a low energy consuming refrigerator with high reliability, low weight, and flexibility in packaging and
- To save energy
- To understand the workings of thermoelectric device
- To digitally display the temperature of the thermoelectric refrigerator
1.4 PURPOSE OF THE STUDY
The purpose of this study is to build a low energy consuming device without moving parts with a digital temperature sensor.
1.5 SCOPE AND LIMITATION OF THE STUDY
The working principle of this study is based on the Seebeck and the Peatier effects. The thermometric effect is a process of the production of electromotive force out of temperature difference on two conductor- or semiconductor-based electronic components, and backwards-temperature difference obtained by applying a DC power. A 12v supply is used while the Peatier module is used as the thermometric cooling device. The temperature sensor DS18S20 was interfaced with PIC16F877A micro-controller to display display the room temperature of the refrigerator.
1.6 APPLICATION OF THE STUDY
The same working procedure used in building this device can also be used with little modification in building:
- Dc air conditioner
- Dc powered Heating device
1.7 SIGNIFICANCE OF STUDY
The research work will enable us to know how the exiting dc refrigerators in the market operate and are build. The result obtained will be used to create awareness and educate the public about the cooling system of dc refrigerator.
This study will also be a means of turning student into a producer of low powered refrigerator after completing this research work thereby becoming self employed which can be later create job opportunity to others..
1.8 METHODOLOGY
To achieve the aim and objectives of this work, the following are the steps involved:
- Study of the previous work on the project so as to improve it efficiency.
- Draw a block diagram.
- Test for continuity of components and devices,
- programming of micro-controller
- Studying of various component used in circuit.
- Construct the whole circuit.
- Finally, the whole device was cased and final test was carried out.
1.9 PROJECT ORGANIZATION
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
CHAPTER FIVE
CONCLUSIONS
Thermoelectric refrigeration solutions are gaining relevance because of a number of positive aspects, such as long duration, noiseless operation, limited maintenance needs, absence of flammable or toxic refrigerants, possibility of being used in different positions and in movable solutions as well as flexibility of usage through optimized control.
At the end of this work, the objective of this work was achieved which involved using direct current with technological system for refrigeration such as thermoelectric and thermionic for application on a large scale because its performance arrived at least 30% this is very promising for use in Nigeria. A thermoelectric air-condition was designed and built which can be used for personal cooling. TECs were used for achieving the cooling with a DC power supply through external power supply. After we had earlier studies the importance of thermoelectric in refrigeration, especially after their integration with dc supply and then the assessment of thermoelectric performance labs, as was the best wineries of the performance of a large cooling capacity at 430 W was 2.6 thermoelectric technology also witnessed great development, use the water to cool and absorb heat from the hot side to improve efficiency and proved its worthiness reliability high so I see in the future to improve the work.
