ABSTRACT
At present, non-renewable energy sources are depleted constantly, Harmful emissions from fossil fuels and chlorine-based refrigerants have led to economic and more severely, environmental hazards. The world has been working to reduce hazardous emissions while developing renewable energy sources and technology. Leading the industry of renewable energy is solar power. By collecting and storing solar heat, and transferring this energy to power an absorption refrigerator, energy efficiency can improve, eradicating usually necessary (poor and sometimes unavailable) electricity.
The development of an inexpensive, modular, small-scale cold room based upon the absorption refrigeration process. This project was developed to proffer means of providing refrigeration to agricultural products in communities lacking or unable to afford conventional energy sources (electrical energy).
A solar-driven ammonia absorption refrigeration system was designed, a modular prototype constructed and tested. It was an intermittent system where ammonia and water were used as refrigerant and absorbent respectively. The main components like evaporator, condenser, and generator were designed based on certain assumptions such as generator temperature 70oc, refrigerating effect of 5 tonnes (for full-scale construction). The necessary heat and mass transfer equations describing the working properties were specified. The theoretical obtained COP was 0.25. Information on designing the condenser, evaporator, and generator of the unit has been presented.
It was assumed that the vapor generating from the generator was 100% pure ammonia vapor. The thermal energy input was calculated to be with Is (solar intensity) = 600 W/m2 where collector efficiency was assumed 30% and collector mirror surface area was 2.3m2, but for purpose of increasing the efficiency, it was the collector area was increased by 20%
TABLE OF CONTENTS
CERTIFICATION 2 DEDICATION 3 ACKNOWLEDGEMENT 4 ABSTRACT 5
CHAPTER ONE 7 INTRODUCTION 9 1.1 Background of Study 9 1.2 Statement of the Problem 9 1.3 Aims of the project 10 1.4 Objectives 10 1.5 Methodology to be adopted 10 1.7 Project Scope 11 2.1 Historical background of refrigeration 12 2.1 Theoretical background solar refrigerator 12 2.1.1 Indices of Performance 12 2.1.2 Operation of the Intermittent Ammonia-calcium chloride System 13 2.1.3 Analysis of the Ideal Cycle 13 2.3 Absorption method 19 2.4 Working principle of vapor adsorption methods 20 2.5 Solar energy 24 2.5.1 Methods of generation 26 2.6 Review of the common structure of cold room 27 2.6 Working Fluid for the Absorption Refrigeration Systems 28 3.1 Materials and material selection 30 Design configuration 30 3.2 Design Conditions for prototype model 31 Condenser design consideration 33 Heat rejection in the condenser 33 Evaporator design consideration 34 3.3 EXPERIMENTAL SETUP (PROTOTYPE) 37 3.4 Experimental procedure (Prototype) 38 CHAPTER 4 40 RESULT AND DISCUSSION 40 4.1 EXPERIMENTAL RESULT 40 4.2 BILLS OF ENGINEERING MEASUREMENTS AND EVALUATION (BEME) 43 4.3 DISCUSSION 43 Chapter 5 45 CONCLUSIONS AND RECOMMENDATION 45 5.1 CONCLUSIONS AND RECOMMENDATION 45
CHAPTER ONE INTRODUCTION 1.1 Background of the Study
Refrigeration is the process of removing heat from a substance under controlled conditions (Muthu et al 1999). Refrigeration uses the evaporation of a liquid to absorb heat. Before mechanical refrigeration systems were introduced, people cooled their food with ice and snow, either found locally or brought down from the mountains. The first cellars were holes dug into the ground and lined with wood or straw and packed with snow and ice. This was the only means of refrigeration for most of history. Moreover, approximately 62 million mew units are being manufactured worldwide every year, and hundreds of millions are currently in. use. (UNEP, 1995) it is anticipated that the production of refrigerator-freezers will substantially increase in the near future as a result of the increased demand, especially in developing countries. Therefore, in response to global concerns over greenhouse resorts are being made to produce refrigerator-freezers with low energy consumption. This project will result in the development of a system that can be a decisive step in bringing refrigeration to the far-off rural areas. This project shall focus on the design of an intermittent absorption refrigeration system; the prototype model will be constructed and tested to observe its functionality.
1.2 Statement of the Problem Local food systems can contribute to socially, economically, and ecologically beneficial food production for local communities. In order to deliver quality products to the consumer, local food systems must utilize rapid cooling and cold storage technology. In the past thirty years, the number of local farms increased 11.2% thus the need for energy-efficient cold storage units (USDA, 2013). Cold storage is essential for vegetable farmers to preserve product quality and extend the revenue period. A personal survey conducted in the oil-rich Niger Delta region that is also blessed naturally with the sources of agricultural products reveals that no development such as reliable solar-powered cold storage has been found in the area whereas the level of food crops production and commercial fishing in the community demand that at least one should be provided. The necessity primarily prompted the essentiality of this study. The studies will also point out that the principle of refrigeration as studied in the classroom would not only remain in theory but can be made tangible in typical practical application in order to be fully, faithfully, and amply appreciated.
1.3 Aims of the project The aim of this project work is to experimentally design and construct a working prototype model of a solar-powered intermittent vapor absorption refrigerator.
1.4 Objectives ⦁ To calculate solar energy and system power requirements ⦁ To construct and test a workable prototype ⦁ To use this project to gain substantial knowledge in solar energy generation and absorption refrigeration cycle. 1.5 Methodology to be adopted To arrive at a successful design and construction, the algorithm below will guide us on the steps to follow: Image Figure 1.6.1 Research/literature review A literature review will be carried out on the existing experimental studies; solar generation methodology will be studied.
1.6.2Design calculations Design considerations such as solar intensity, power requirement, material heat conductivity, heat rejected, energy balance, etc.
1.6.3Materialsselection Appropriate materials will be selected bearing in mind the following objectives ⦁ Low cost ⦁ Availability to local manufacturers ⦁ Less weight ⦁ Heat lagging properties.
1.6.4 CAD model and thermal analysis Solid Works engineering software will be used to produce a CAD model of the design and thermodynamic analysis will be done to give a better understanding of the design.
1.6.5 materials acquisition Material for the construction will be locally sorted for, the evaporator; condenser, etc. will be acquired in the local market.
1.6.6 construction Finally, a workable prototype will be fabricated on a reduced scale to experimentally represent the solar-powered VAR system.
1.7 Project Scope The scope of this project is limited to design calculation, material selection, CAD model, and fabrication of a working prototype. The prototype to be constructed will use an alternative heat emitting body to represent the sun (solar), where the is no good weather during testing.
