CHAPTER ONE
INTRODUCTION
1.1 Background of the Study
If the heat energy possesses the advantage to be “clean”, free and renewable, then this is probably considered as an adapted potential solution, which answers in even-time at an economic pre-occupation and ecological problem. Among the main research done, it is found that refrigeration system uses this free and renewable source. Among all the domestic and industrial appliances used today, refrigerators consume a considerable amount of energy. Using heat energy to run refrigerators is of great practical relevance nowadays.
The recovery of waste energy or waste heat recovery is heat, which is produced in a process by way of fuel combustion or chemical reaction and then dumped into the environment, even though it could still be re-used for some useful financial resolutions. In water cooled engines, the one third of the energy is wasted in exhaust gases. For such cases, vapour compression air conditioning system is used for cooling of cabins and in preservation of goods on board a ship.
1.1.1 Refrigeration Systems and Applications
Refrigeration is the process of removing heat from an enclosed space, or from a substance, and moving it to a place where it is unobjectionable. The primary purpose of refrigeration is lowering the temperature of an enclosed space or substance and then maintaining that lower temperature. The term “cooling” refers to any natural or artificial process by which heat is dissipated. The process of artificially producing extreme cold temperatures is referred to as cryogenic.
1.1.2 First Refrigeration Systems
The first known method of artificially refrigeration was demonstrated by Williams Cullen at the University of Glasgow in Scotland in 1756. Cullen used a pump to create a partial vacuum over a container of Di-ethyl ether, which then boiled absorbing heat from the surrounding air. The even created a small amount of ice, but had no practical application at the time.
In 1805, American inventor Oliver Evans designed but never built a refrigeration system based on the vapour compression cycle rather than the chemical solutions or volatile liquids such as ethyl ether. In 1820, the British scientist Michael Faraday liquefied ammonia and other gases by using high pressures and low temperatures. An American living in Great Britain, Jacob Perkins obtained the first patent for a vapour compression refrigeration system in 1834. Perkins built a prototype system and it actually worked, but it never succeeded commercially.
The first gas absorbing refrigeration system using gaseous ammonia dissolved in water (referred to as “aqua ammonia”) was developed by Ferdinand Carre of France in 1859 and patented in 1860. Due to the toxicity of ammonia, such systems were not developed for use in homes, but were used to manufacture ice for sale.
1.1.3 Current Applications of Refrigeration
Probably, the most widely-used current applications of refrigeration are for the air conditioning of private homes and public buildings, and the refrigeration of foodstuffs in homes, restaurants and large storage warehouses. The use of refrigerators in our kitchens for the storage of fruits and vegetables has allowed us to add fresh salad to our diets year round, and to store meat and fish safely for long periods.
In commerce and manufacturing, there are many uses for refrigeration. Refrigeration is used to liquefy gases like oxygen, nitrogen, propane and methane. In compressed air purification, it is used to condense water vapour from compressed air to reduce its moisture content. In oil refineries, chemical plants, and petrochemical plants, refrigeration is used to maintain certain processes at their required low temperatures (like in the alkylation of butane and butane to produce a high octane gasoline component). Metal workers use refrigeration to temper steel and cutlery. In transporting temperature-sensitive foodstuffs and other materials by trucks, trains, airplanes, and sea-going vessels, refrigeration is a necessity.
1.1.4 Waste Heat Recovery On Board Ship
Waste heat recovery system involves collecting waste heat rejected by the plant and equipment (like refrigeration plants) and using it for other heating applications such as domestic hot water, wash down water, boiler feed water and even sterilization. The system can consist of an exhaust gas boiler (or combined with oil fire boiler), a powerful turbine and a steam turbine with alternators. It is well proven on board ships, but the potential can be variable depending on the size, numbers, usage and efficiency of the engines on board the ship.
1.1.5 Applicability and Assumptions
This technology can be applied to all ships regardless of size, age and type, even though it seems to have a practical lower limit on the engine size of 10MW at present. The effect is assumed to be constant, on vessels operating at high enough engine loads. The benefit from this technology can be twofold; In terms of reduced fuel consumption on either a main engine equipped with shaft generator or on the traditional auxiliary engines.
1.2 Aim
The main aim of the study is to increase the coefficient of performance (COP) of the system by utilizing waste energy.
1.3 Objectives
The objective of the work is therefore;
To employ the exhaust gas of an internal combustion engine to run a vapour absorption refrigeration system (VAR) of a fishing trawler
To develop a simple vapour absorption refrigeration system(VAR) model using exhaust gas from diesel engine on three fluid vapour absorption systems and
To thermodynamically evaluates the model to determine the performance parameters of a fishing trawler
1.4 Problem Statement
Refrigeration plays a vital part in the preservation of perishable cargoes and provisions for the crew onboard vessels. In merchant vessels, the temperature of victuals and cargoes such as food, chemicals, liquefied gas etc. are controlled by the refrigeration plant of the ship. The main purpose of ship refrigeration plant is to prevent loss of the cargoes or perishables so as to ensure their safe transportation in good and healthy condition (Anish, 2016).The potentials inherent in converting heat and wasted energy from exhaust gas of ships is on the high. This firstly, mitigation of environmental pollution is applied here and a VAR type system can be supplied with this energy since they are mainly low grade energy and consist of mainly heat. Instead of allowing this waste heat to cause environmental hazards, the study examines how these heat can be converted to aid refrigeration by increasing the coefficient of performance (COP) of the system by utilizing waste energy.
1.5 Scope of Research
The scope of this research work focuses on the design analysis of cooling system for a ship, using waste heat of the engine exhaust, without much effort on the engine performance.
Poku [6] studied the viability of VARS employing water-lithium Bromide (LiBr-H2O) as refrigerant-absorbent pair. Recovered waste heat from the exhaust gas of a diesel engine was used as the heat source. The study showed that with exhaust gas temperature of 850C, Coefficient of Performance (COP) of 0.85 is feasible. The air conditioning system of an automobile with the application of waste heat from the engine was investigated by Mauryaet al. (Maurya, Awasthi, and Siddiqui, 2014). In this system, as an alternative power from the engine shaft as the input power to drive the compressor of the refrigeration system, waste heat from the vehicle is employed to produce the refrigeration effect. The benefit is, the engine does not need to produce extra work to run the compressor of the refrigerating system, hence saving fuel consumption.
