الفهرس 
ch 1 : IntroductionOnly 14 pages are availabe for public view
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Abstract
Since a large amount of energy is wasted in the atmosphere by the exhaust gases and coolant for diesel engine. In addition, the emission pollutants increased remarkably at low environment temperatures due to misfiring and incomplete combustion causing the start-up of the diesel engine to be difficult. In this study, a new design of the exhaust waste heat recovery (WHR) system using phase change materials (PCMs) was established for saving energy and decreasing engine emissions. The transient melting process of the PCM is controlled by heat conduction and natural convection, which are essential to understand the PCM heat transfer mechanisms. Here, the melting process of the paraffin wax was studied in a vertical cylindrical enclosure. Local temperatures of the PCM were measured, and the solid-liquid interface was tracked. A CFD (computational fluid dynamic) model was developed to numerically investigate the melting process. The results showed that: the melting was initially dominated by conduction at an early stage, and this period increased with a decrease in heat flux. Natural convection was promoted, at a later time, leading to a curved shape of the solid-liquid interface. Numerical results indicated a robust thermal stratification of the molten liquid in the upper half of the storage unit. The WHR system was divided into three cycles ; preheating cycle, absorption cycle, and photovoltaic cycle. The preheating cycle was used to decrease the emissions in the cold start-up period and the absorption cycle with a photovoltaic cell was used to decrease the emissions in the normal condition. The aim of the proposed WHR system can be concluded as follows : Firstly, preheat the intake air before admitting it into a diesel engine through the cold start-up conditions by using exhaust gas energy. The preheating system has a ribbed plate heat exchanger (H.EX) that acts as a storage unit filled with paraffin wax. The influences of height and spacing of ribs, nanoparticles type (SiO2, Al2O3, and CuO) and weight fraction (2.5, 5, and 7.5 w.t%), stored energy, engine rotational speed, and intake air temperature were investigated. During the charging process, the highest thermal performance of the storage unit occurred at SiO2 nanoparticles with a weight fraction of 5 w.t%. During the discharging process, after less than 1 min, the cold intake air can be heated from the ambient temperatures of 273 and 268 K to 301.8 and 300.6 K, respectively. Secondly, operating the absorption cycle in automobile air conditioning (A/C) systems at low engine speeds by using exhaust gas energy. Because of the main challenge of the absorption cycle in automobile air conditioning (A/C) systems is the use of exhaust energy to drive the system at low engine speeds. To obtain a continuous supply of cooling energy from the absorption cycle. The novel generator design in an absorption system using an H2O-LiBr solution as the working fluid was proposed. The generator heat exchanger (H.EX) was divided into several cells filled with multiple phase change materials (PCMs) acting as storage units. The effects of multiple types of PCM, coefficient of performance (COP), and solution temperature were studied at low and high engine speeds. At low engine speeds, exhaust energy could drive the absorption system with COP values of 0.767 and 0.778, while in the case without PCM, exhaust energy could drive COP values of 0.284 and 0.763 for engine speeds of 1500 and 2000 rpm, respectively. At high engine speeds, the system performance was roughly stable with a slight increase in COP values. Finally, using the photovoltaic phase change materials (PV-PCMs) system to operate the pumping power in the absorption system and any other electrical accessories in the engine to save fuel and decrease emissions. The system consists of a separated convex/concave dimpled aluminum plate and multiple PCMs as a heat sink. The electrical power of the PV-PCMs system is roughly about 12.50 W, while the pumping power for the high and low engine speeds is 6.60, 2.89 W, respectively.