Solar energy can be utilized by, either, thermal conversion, or electrical conversion, of solar radiation. Utilization of solar energy by thermal conversion method, is of low cost, but it requires high density of solar radiation. Electrical conversion method, on the other hand, is expensive, but it does not need high density of solar radiation. One of the most important applications of thermal conversion of solar energy, is absorption refrigeration. As there are many factors affecting the process of solar refrigeration, a lot of research work must be carried out, before deciding an optimum design of solar refrigeration systems, which utilize solar energy at a low cost. The main objective of this research article is to design and construct an apparatus which can be used, as a test rig, by research students, to carry out experiments, regarding the performance of solar absorption refrigeration systems. The apparatus has been designed and constructed so as to be used indoors. One of the many different factors which affect the performance of solar absorption refrigeration systems, has been chosen, to test the apparatus, for functioning. This is the effect of condenser temperature, on the performance of solar absorption refrigeration systems. The apparatus has been tested for three different values of condenser temperature, and yielded very good results. The experimental work proves that, the coefficient of performance of a solar absorption refrigeration system, is high, at a low condenser temperature. At a condenser temperature of about 25ºC, the actual coefficient of performance, obtained is 0.019, compared with a theoretical value of 0.062. And at a condenser temperature of about 15ºC, the actual coefficient of performance is 0.026, compared with a theoretical value of 0.094.
Table of Contents
I. INTRODUCTION
II. LITERATURE REVIEW
1. Solar energy
2. Refrigeration
3. Solar Absorption Refrigeration
4. Properties of Aqua-Ammonia Solution in Absorption Cycles
III. MATHEMATICAL MODELING OF THE SYSTEM
1. Description of the System
2. Analysis of the Flat Plate Collector
3. Generator Analysis
4. Condenser Analysis
5. Absorber Analysis
7. The Simulation Program
IV. DESIGN AND CONSTRUCTION OF THE SYSTEM MODEL
1. Specifications
V. EXPERIMENTAL WORK
1. Apparatus
VI. CONCLUSIONS AND RECOMMENDATIONS
1. Conclusions
2. Recommendations
Research Objectives and Themes
This research focuses on the design, construction, and performance analysis of an indoor, intermittent ammonia-water solar absorption refrigeration test rig. The primary objective is to develop a simulation program to predict system performance under varying conditions and to validate this model through experimental testing, specifically investigating the impact of condenser temperatures on the coefficient of performance.
- Design and construction of an intermittent ammonia-water solar absorption apparatus.
- Development of a computer simulation program for system performance prediction.
- Experimental evaluation of the system under different condenser temperature settings.
- Mathematical modeling of system components, including flat plate collectors and heat exchangers.
- Comparison of theoretical simulation results with experimental data.
Excerpt from the Book
Generator/Absorber
This is a single vessel, it is a shell type heat exchanger. It consists of a shell of 100 mm inner diameter, and three tubes each of 16 mm inner diameter, located inside the shell, Fig. 3. The shell is filled, up to about 60% - 80% of its volume, with a strong solution of aqua-ammonia of known concentration. The exact mass of the solution depends on the size of the model required. When working as a generator, steam and/or hot water is allowed to enter from the flat-plate collector through the tubes inside the shell and then back to the collector. The heat is transferred from the hot water, inside the tubes, to aqua-ammonia solution surrounding the tubes inside the shell, and hence the solution temperature and pressure increase. When the solution pressure reaches the saturation pressure, corresponding to the condenser temperature, ammonia starts to evaporate from the aqua-ammonia solution, and passes to the condenser coil, where it condenses to liquid ammonia, and flow, by gravity, to the receiver. The generation of ammonia vapor is expected to continue for a period of about 5 to 6 hours, during which the required quantity of ammonia liquid will be evaporated, condensed and stored in the receiver. During the absorption cycle, cold water is allowed to flow from the absorber cooling water tank, and enter to the tubes, which, are immersed in the aqua-ammonia solution inside the shell, and then back to the tank, or to the drain. The sudden cooling of the absorber reduces the temperature and, consequently, the pressure of the weak ammonia-water solution. The pressure in the absorber, therefore will be less than the pressure of pure ammonia in the receiver, hence, ammonia liquid, in the receiver, vaporizes, causes cooling effect there, and flows back, to be absorbed by the weak solution, in the absorber. The absorption process releases heat, so that continuous cooling of the absorber is required, throughout the absorption cycle.
Summary of Chapters
I. INTRODUCTION: Discusses the global energy crisis, the limitations of petroleum, and the potential of solar energy as a renewable alternative for refrigeration in tropical climates.
II. LITERATURE REVIEW: Provides a comprehensive overview of solar radiation, refrigeration principles (vapor compression vs. absorption), and previous studies on solar intermittent absorption cycles.
III. MATHEMATICAL MODELING OF THE SYSTEM: Presents the thermodynamic equations and subroutines used for the computer simulation, covering component analysis for collectors, generators, condensers, absorbers, and evaporators.
IV. DESIGN AND CONSTRUCTION OF THE SYSTEM MODEL: Details the design specifications, materials used, and ergonomic considerations for the experimental rig, based on British Standard recommendations.
V. EXPERIMENTAL WORK: Describes the apparatus setup, testing procedures for regeneration and absorption cycles under different condenser temperatures, and the resulting experimental data.
VI. CONCLUSIONS AND RECOMMENDATIONS: Summarizes the findings regarding performance improvements at lower condenser temperatures and provides suggestions for future research using advanced measurement techniques.
Keywords
Solar energy, absorption refrigeration, ammonia-water, intermittent cycle, flat plate collector, system design, performance analysis, mathematical modeling, computer simulation, condenser temperature, heat exchanger, thermal conversion, energy conservation, experimental rig, cooling load.
Frequently Asked Questions
What is the core focus of this research?
The research focuses on the design, construction, and experimental performance evaluation of an intermittent ammonia-water solar absorption refrigeration system intended for use as an educational test rig.
What are the primary thematic fields covered?
The study spans thermodynamics, solar energy engineering, refrigeration cycles, mathematical modeling, and experimental design within a laboratory setting.
What is the main research objective?
The main objective is to design and construct a test rig to facilitate research into solar absorption refrigeration, and to write a computer program that predicts system performance under various operational parameters.
Which scientific method is utilized in this study?
The study combines analytical mathematical modeling of system components with experimental testing. Theoretical results generated by a computer program are compared against empirical data collected from the test rig.
What does the main part of the work address?
The main body treats the derivation of heat and mass balance equations, the design specifications of the apparatus components (generator, condenser, receiver), and the test procedures followed for data collection.
Which keywords characterize this work?
Key terms include solar absorption refrigeration, ammonia-water, intermittent cycle, system design, thermal performance, and coefficient of performance (COP).
How does the condenser temperature affect system performance?
The experimental results demonstrate that the coefficient of performance of the system increases as the condenser temperature decreases, indicating that lower condenser temperatures enhance efficiency.
Why is an indoor model preferred in this research?
An indoor model allows for controlled experimental conditions and eliminates dependence on unpredictable outdoor solar radiation, thereby facilitating accurate, long-term data recording.
What is the role of the aqua-ammonia solution properties in this study?
The thermodynamic properties of the aqua-ammonia mixture—such as concentration, pressure, and enthalpy—are critical for predicting the phase changes and performance of the absorption cycle at various stages.
- Citar trabajo
- Associate Professor Osama Mohammed Elmardi Suleiman Khayal (Autor), Dr. Fathelrahman Ahmed Elmahi (Autor), 2004, Utilization of Solar Energy in Absorption Refrigeration, Múnich, GRIN Verlag, https://www.grin.com/document/540530
