Mechanical Engineering
144 theses under this subject heading
Dynamics Analysis of Viscoelastic Sandwiched Structures Integrated with Aluminum Sheets by Using Finite Element Method
Passive vibration attenuation of modern mechanical structures is one of the most essential technologies applied to the arsenal of modern mechanical structures. In this thesis, dynamics analysis is performed on viscoelastic (VE) beam and plate sandwich structures. The proposed structures are composed of a VE core and aluminum face sheets as the substrate layers on both sides of the structure. The small-strain VE material is modeled based on the complex constant moduli model. In the modal analysis, the model effective mass analysis is performed to investigate its dominant mode shape and its sweet spot at resonance. Then, in the harmonic analysis, the resonance frequency is obtained to evaluate the performance of the VE sandwich structures via the maximum deformation. A comparison between the results of an analysis of viscoelastic sandwiched structures with subsequent done using FE models. A numerical application is accomplished to develop the integral shear finite element and modal assembly of the stiffness element and mass element established according to strain energy and the Hamilton principle. The harmonic analysis is done using ABAQUS® software with both C3D20RH®, CPS8R where C3D20RH indicates a 3- D element with 20 nodes with reduced integration technique and hybrid formulation and CPS8R indicates 2-D plane strain with eight nodes with reduced integration technique, the results are compared against analytical solutions form the literature, a parametric study is done on the beam’s core thickness to study the effect on the damping characteristics of the beam, the results showed that the modal developed in MATLAB® achieved the least error compared to the analytical solution from the literature and then comes the Abaqus® software solution, also the parametric study showed that the natural frequency of the beam does not change with the increase of the core thickness, however, the loss factor is directly proportional to the thickness of the viscoelastic layer of the beam. Keywords: Viscoelastic, Sandwich Beam/Plate, Dynamics Analysis, Complex Constant Moduli, Finite Element Method, Shear Deformation Theory
Simulation of Flexural and Tensile Properties of Additively Manufactured Continuous Carbone Fiber
The act of additive manufacturing (AM) entails layer by layer creation of a layered structure from the ground up. This competence allows for a sophisticated design to be carried out with geometries that are sometimes impossible to achieve and materialize with conventional manufacturing methods such as subtractive manufacturing, molding, foaming, etc. Fused filament fabrication (FFF) or sometimes addressed as fused deposition modeling (FDM) is among the AM methods which couples well with manufacturing composite materials. Fabricated composite materials using FFF has proven to be particularly useful in a plethora of industries, namely in the aerospace and aeronautics, automotive industry, therapeutic apparatuses, and sports goods. In general, invented parts with FFF method have excellent mechanical properties which make them worthy of further study. Performance under tensile tension and flexural (bending) tensions are particularly significant in composite materials. Therefore, a thorough finite element modeling (FEM) on tensile and flexural behavior of FFF fabricated continuous carbon fiber specimen in the COMSOL multi-physics® environment is executed while using layered shell elements to express the properties in a layered structure. The results gathered from the FEM was compared to other experimental and related empirical studies. Furthermore, the type of effects a composite material might have on tensile properties such as infill ratio, infill pattern, fiber content, layer orientation and stacking sequence will be put under scope. Based on the results provided under this new study, the tensile and flexural simulated specimen shown better maximum tensile and flexural capabilities, with 1490 [MPa] and 1240 [MPa] Max stress, while the tensile model underwent the boundary load of 559.9 MPa and the flexural model went through 302.70 N at two points to simulate the two-point flexure test.
Application of Metaheuristic Search Algorithms for Path Planning of Smart Vehicles
Navigating a smart vehicle in an environment, determined or unknown, requires the localization of such vehicle in that environment using GPS, cameras, vision, laser or ultrasonic sensors, motion planning of the vehicle in free configuration space of the environment, and its ability to deviate from obstacles. In planning a path from a start to a goal configuration, the aim is to obtain the shortest path in less time while avoiding obstacles. Metaheuristic algorithms have been extensively applied to achieve this; while it exploits the environment from an initial solution, it also explores it to find a possible feasible path. Researchers in robotics and automation field have investigated and analysed the performance of population-based algorithms like Genetic Algorithm (GA), Ant Colony Optimization (ACO), Particle Swarm Optimization (PSO), Firefly Algorithm (FA), and Cuckoo Search Algorithm (CSA) to obtain a feasible shortest path. This research work investigates the performance of metaheuristic search algorithms like GA, PSO, FA, and CSA for path planning on four different benchmark problem maps (40 x 40m large, 20 x 20m maze, 20 x 20m rockpile and 20 x 20m pothole) and makes a comparative analysis based on computational time and path length. Furthermore, three sampling methods i.e., Random, Latin hypercube and pseudo-uniform sampling were used. It is observed that all the algorithms were able to achieve the optimal, although CSA performed poorly on path distance using GA and PSO on the maze and pothole map respectively, its performance on other two maps was relatively better both on shortest distance and computational time, however, it is concluded that no single algorithm is universally the best-performing algorithm for all maps. All simulations were performed on MATLAB R2022b. Keywords: Metaheuristic Algorithms, Path Planning, Navigation, Mobile Robot, Smart Vehicle
An Experimental Study of Natural Convection of Nanofluid in a Rectangular Cavity
The concept of nanofluids refers to a new kind of heat transport fluids by suspending nano scaled metallic or nonmetallic particles in base fluids. The experimental results showed that the suspended nanoparticles increased convective heat transfer coefficient of the fluid. The properties and behavior of a nanofluid depend on a number of parameters including the properties of the base liquid and the dispersed phases, particle concentration, particle size and morphology, as well as the presence of dispersants and/or surfactants. From a macroscopic view, the properties of homogenous nanofluids that affect the heat transfer behavior include heat capacity, thermal conductivity, density and viscosity. Natural convective heat transfer is affected by a number of processes in parallel and/or series, including unsteady state heat conduction through the heating wall, conduction within the boundary layer and its development, as well as convection due to the variation of liquid density and the density difference between the nanoparticles and the liquid. In this experimental study, natural heat transfer of Nanofluid will be investigated. Nanofluid with different volume percentage will be put between walls of the cavity, and the natural heat transfer will be observed. As a result of the experimental readings, Nusselt number as a function of Rayleigh number (i.e. Nu= c Raⁿ) will be obtained.
Thermodynamic Study of the Supercritical, Transcritical Carbon Dioxide Power Cycles for Utilization of Low Grade Heat Sources Application
Low-grade heat (LGH) sources, here defined as those below 500 oC, are a group of abundant energy sources available as industrial waste heat, solar thermal, and geothermal which are not used to their full advantages. For example, they are not adequately for conversion to power because of low efficiency energy conversion. The utilization of LGH can become advantageous for achieving to the highest thermal efficiency. Technologies that allow the efficient conversion of low-grade heat into mechanical and electrical power need to be developed. Various studies have been carried out to appraise the potential of using supercritical carbon dioxide (S-CO2) in a closed Brayton cycle using LGH source for power generation. In this study, the objective of research is to perform a thermodynamic analysis on five different configurations of S-CO2 Brayton cycle. Different configurations are examined among which recompression and partial cooling have been found very promising. The main part of this study is focused on carbon dioxide Brayton cycle. CO2 Brayton cycle has wide range of applications such as heat and power generation and in automotive and aircraft industry. Proposed configurations of each carbon dioxide Brayton cycle performance simulation are conducted and subsequently compared with other power cycles utilizing LGH sources. The CO2 transcritical power cycle (CDTPC) utilizing LGH is also studied. The models are developed by using the Engineering Equation Solver (EES) for several different Brayton cycle configurations. The choice was made to pursue Brayton cycle with regeneration configuration for further, due to its simplicity and high efficiency. Keywords: Supercritical CO2 Brayton cycle, transcritical CO2 cycle, simulation, low-grade heat.
Design and Experimental Investigation of a Novel Solar Crop Dryer
The motivation of this research project was in response to issues of increasing energy demand and the surge in energy scarcity and environmental problem. Various form of fuel like oil, natural gas, wood, and coal etc. can be used for drying process but they are not cheap, and most of them are not environmentally friendly. Renewable energies are one of the promising ways to tackle this global challenge. This work is centered on the investigation solar drying process. A mix-mode solar dryer was designed for drying fruits, vegetables, and biomass. The dryer is made up of a flat plate solar collector, duct fan, two drying chamber module glazed from the top. The flat plate collector of length 200 cm, width 100 cm and height 20 cm was use to preheat the air before entering the drying chamber. The collector is made up of 3mm thick double layer of glass, V-corrugated sheet metal with 60° groove angle. A duct fan is used to provide air circulation. The drying chamber is manufactured from steel, wood, and glass. Different tests were carried out to evaluate the performance of the dryer. The dryer was used to dry apple, banana, grapes and chili pepper. For the different tests carried out the temperature, humidity and solar radiation was recorded to enable evaluation for the performance parameters such as moisture content at the end of each day, drying rate, and drying efficiency. The moisture content of apple, banana, grapes and chili pepper was reduced to their final moisture content within two days of sunshine hours. The average drying rate for apple, banana, chili pepper, and grapes were found to be 30.2 g/h, 82 g/h, 67.8 g/h and 98 g/h respectively per kg of each specimen. Keywords: Solar drying, mix-mode solar dryer, food crop and drying chamber
Numerical Investigation of Copper-Water Nanofluid in a Parallel Plate Channel
ABSTRACT: Heat transfer behavior of Cu-water nanofluid in a two dimensional (infinite depth) rectangular duct is studied numerically for laminar flow, where the nanofluid has been considered as a Newtonian fluid. The governing continuity, momentum, and energy equations are discretized using finite volume approach and solved using SIMPLE method. The viscosity and thermal conductivity of nanofluid are determined by models proposed by Brinkman and Patel et al. Study has been conducted for a wide range of Reynolds number from 10 to 1500, for solid volume fractions between 0% and 5%. Top and bottom walls are considered for two cases of constant temperature and constant wall heat flux, while results for both uniform and parabolic entrance velocities are considered in each case. It has been observed that the rate of heat transfer increases with increase in solid volume fraction as well as increase in flow rate. Besides, higher heat transfer is observed for uniform entrance velocity compared to channel with parabolic inlet velocity. Keywords: Nanofluid, Rectangular duct, Laminar flow, Newtonian. …………………………………………………………………………………………………………………………
Experimental Study on the Slit Glazed Solar Air Heater
The energy demand all over the world has been continuously increased. The ever increasing cost, limited resources and possible environmental risks of using conventional energy resources have increased the renewable energy utilization. Solar energy is considered the most promising, inexhaustible and plentiful renewable source of energy. Solar collectors are employed in converting solar energy into thermal energy. The energy consumption of space heating in residential and industrial sector is considerable. In solar energy utilization direct use for space heating could be achieved by employing solar air heaters (SAHs). Technical feasibility has been achieved for SAHs. One of the main concerns is providing economic feasibility. The present study consists of three series of experiments. First, three SGSAHs with different bed heights (7 cm, 5 cm, and 3 cm) were fabricated with multiple glass panes used for glazing. The length, width, and thickness of each pane were 131 cm, 6 cm and 0.4 cm respectively. The mass flow rate was varied between (0.014 and 0.057) kg/s. The second series of experiments had been conducted to investigate the effect of the width of glass panes, the distance between the slits and mass flow rates on the efficiencies of the three SGSAHs. A glass pane with the length of 131 cm and thickness 0.4 cm was studied for three different glass pane widths: 6 cm, 5 cm, and 4 cm. In addition, the bed height of duct in the second series of experiments was fixed at 7 cm. The ambient air was continuously withdrawn through the gaps between the glass panes by fans. In the first and second series, the experiments were conducted for four different gap distances between the glass panes (i.e., 0.5 mm, 1 mm, 2 mm and 3 mm). Finally, the third series of experiments had been carried out on a SGSAH and a UTC to compare their efficiencies. The mass flow rates in the second and third series of experiments were varied between (0.014 and 0.029) kg/s. In the first series of experiments the highest efficiency obtained was 82% where the bed height was 7 cm, glass pane gap distance was 0.5 mm, and the mass flow rate was 0.057 kg/s. The air temperature difference between the inlet and outlet (∆T) was maximum (27˚C) at the lowest mass flow rate (i.e., 0.014 kg/s) for the same SGSAH. The results demonstrated that for mass flow rates lower than 0.036 kg/s and gap distances greater than 2 mm, the performance of the SGSAH with 3 cm bed height was better compared to the SGSAHs having 5 cm and 7 cm bed heights. However, for flow rates equal or higher than 0.036 kg/s, the SGSAH with 7 cm bed height performed better for all different gap distances compared to the other two SGSAHs. The experimental results of the second series indicated that the maximum thermal efficiency of 75% was obtained when the gap distance was 0.5 mm, slit width was 4 cm and the mass flow rate was 0.029 kg/s. The maximum rise in air temperature was noted as 28℃ at the lowest mass flow rate where the gap distance and slit widths were 0.5 mm and 4 cm respectively. The experimental results obtained from the last series indicated that the thermal efficiency of the SGSAH was 16% higher than the UTC’s efficiency. Keywords: Slit glazed solar air heater, thermal efficiency, unglazed transpired collector, bed height
Experimental Investigations of Thermochemical Heat Storage System Using Hydrated Salt Based Composite Sorbents for Building Space Heating Applications
Energy is one of leading problem all around the world. Increasing urbanization and industrialization, improving life conditions and standards and increasing world population have been creating a dramatic rise of energy demand. As a consequence of population growth, this resulted in high rate fossil fuel consumption. Besides, use of fossil fuels creating irrecoverable environmental damages such as global warming. Renewable energy and its storage systems are most promising solutions to overcome this problem. North Cyprus is an island good and suitable candidate for renewable energy utilization and its storage applications. Particularly, solar energy is abundant throughout year in North Cyprus and it represents a high potential to be used for building space heating. The main barrier is the imbalance between the heating demand and solar energy availability. Due to the cyclic nature of it, there is no solar radiation available at nighttime once the heat losses increasing. This condition indicates the need of utilizing thermal energy storage coupled with solar collector systems to store the solar energy once it is available to be used later when it is needed. Despite latent and sensible heat storage systems have been researched widely for this purpose, they have some major drawbacks such as low energy storage density and high heat losses limiting the storage potential and duration. A new thermal energy storage method; thermochemical heat storage, based on reversible sorption-desorption cycles is purposed in this study. Such thermal energy storage system could provide higher heat storage density and long-term heat storage potential making it attractive for solar thermal applications. From this point of view, aim of the presented study is; to develop a prototype thermochemical heat storage system and to test it under laboratory conditions. A novel composite sorption material; CaCl2–Vermiculite was synthesized and used as the heat storage material. Three different cycles (discharging-charging) with the same flow rate were carried out. Throughout the testing, some optimal results were obtained. For charging temperature between 80-90 °C, discharging average temperature lift of air between 15-20 °C was obtained. Besides, cumulative energy output in the range of 1.6-1.8 kWh was attained, corresponding to an energy storage density between 200-230 kWh. Observed results in this experimental study demonstrated that, for both long and short term heat storage, thermochemical process using V-CaCl2 sorbent is satisfactorily promising and a good candidate to be utilized in solar thermal applications in buildings for sustainable space heating.
Failure Mode and Effect Analysis (FMEA) of Gas Turbine Power Plant System (GTPPS)
Failure Mode and Effect Analysis (FMEA) is an approach used for the system reliability analysis. In the present work, FMEA is applied to Gas Turbine Power Plant System (GTPPS). A total of 44 probable failure modes of main subsystems (i.e. compressor, combustion chamber, turbine, and generator) and auxiliary subsystems (i.e. fuel, oil, and electrical subsystems) have been identified and prioritized based on FMEA. The list of failure modes is ranked according to the assigned values in four different FMEA approaches: 1. Risk Priority Number (RPN), 2. Fuzzy RPN based on 10 membership functions, 3. Fuzzy RPN based on 100 membership functions, and 4. Aggregated Fuzzy RPN, where the higher the assigned values indicate the higher rank of criticality for the related failure mode. Furthermore, based on the obtained results, the analysis precision of the utilized approaches is compared and the type of required maintenance activity is proposed for critical failure mode as well. Keywords: Gas turbine, Failure mode and effect analysis, Power plant, Maintenance policy
Effect of helmet in preventing human head and brain trauma in traffic accidents
ABSTRACT: To date, there have been number of studies to demonstrate the effectiveness of helmet during head impacts in car or motorcycle accidents, but these studies were focused on frontal impacts to the head only. There is still a need to study more on helmet to make it more effective, especially in lateral impacts. To my knowledge, previous studies did not focus on the effects of helmet during lateral impacts. This study focuses on lateral impacts and how the helmet prevents head injuries during such impacts. In this thesis, 3D models of the human head and helmet were created in order to build a parameterized Finite Element (FE) model of a protected human head. In the FE model, brain is assumed to be hyper-elastic, the helmet is considered as elasto-plastic and the skull is considered as a linear elastic material. Two separate FE analyses were carried out in this study to find out how the helmet prevents lateral impacts to the head. In the first analysis, the head was not protected and it hits the impact object directly. In the second analysis the head model is protected with a one-layered helmet. In each of these simulations normal and Von Mises stresses are calculated and in the end compared with each other in order to understand the influence of helmet in reduction of such stresses on human head. Afterwards the acceleration of center mass of the head during two simulations are calculated and compared to each other. Helmet reduces head acceleration by 83%, which is a very important cause of Traumatic Brain Injury (TBI). It is clear that the helmet can be very crucial in avoiding brain trauma during car accidents under lateral impacts. ………………………………………………………………………………………………………………………… Through applying more sophisticated modeling in the FEA, the stress distribution at each layer of the helmet and at each part of the head could be illustrated. Therefore, this knowledge will provide insight into designing and developing helmet and safety products to reduce head and brain trauma. Keywords: Traumatic Injury, Helmet, Lateral Impacts, Head, Biomechanics.
An RFID - based distributed control system for flexible manufacturing system
ABSTRACT: A modern flexible manufacturing (FMS) system typically consists of several distributed control systems, such as machining stations, assembling stations, material handling and storage systems. Employing new technologies and novel approaches on a FMS results to more flexibility, agility and re-configurability. The application of Radio Frequency Identification (RFID) technology in the manufacturing systems provides the basis for accomplishing more flexible and agile systems by utilizing real-time information of the components. Modeling an RFID-enabled FMS is necessary, so as to evaluate the design, measure the performance and translate the resulting models into operational applications. However, these processes are complex but very vital in implementation of the new technology. This thesis (a) presents the architecture for modeling an RFID-enabled flexible manufacturing system.(b) discusses the architecture devised to deploy RFID-enabled distributed control and monitoring system by means of a set of agents that are responsible for the realization of different control and monitoring tasks and cooperating with each other to enhance agility, flexibility and re-configurability of manufacturing system. The primary focus is on, requirement analysis of the manufacturing system, design and development of RFID-enabled manufacturing system using Unified Modeling Language (UML) diagrams that ensure systems integration with more flexibility and re-configurability, using efficient algorithms and effective tools and applications for implementing RFID-enabled architecture for the FMS. The RFID-enabled distributed control and monitoring system has been explored using a flexible manufacturing system (EMU- CIM lab) to demonstrate the feasibility of the proposed architecture successfully. Keywords: Flexible Manufacturing (FMS) System, Radio Frequency Identification (RFID) Technology, Unified Modeling Language. ………………………………………………………………………………………………………………………………………………………………………………………………………… OZ: Modern esnek üretim sistemi genellikle bir çok kontrol sistemlerinde oluşur ki,buna imalat istasyonları,montaj istasyonları,malzeme taşıma ve depolama sistemleri dahildir. Üretim sistemi sonuçları üzerinde yeni teknolojiler ve yenilikçi yaklaşım istihdamı daha fazla esneklik,çeviklikle sonuçlanır.Radio frekansı uygulama teknolojisi imalat sistemlerinde gerçek zamanı kullanarak geçiş ve esnek sistem sağlar. Üretim sistemi modellemesinde radio frekansı ile tanımlama özelliği gereklidir,böylece tasarım değerlendirildiğinde performans ölçer ve operasyon uygulamalarını çevirir. Ancak, bu yöntem karmaşık olsada yeni teknolojinin uygulanmasında hayati rol oynar. Bu tez, a) radio frekansı tanımlama özelliği ile esnek üretim sistemi için mimari modelleme sunar. b)radio frekansı tanımlama özellikli kontrol sisteminin mimari keşfi açışından tartışır ve izleme sistemi hangi farklı kontrollerin gerçekleşmesi için sorumlu, izleme görevleri ve çeviklik,esneklik üretim sistemini geliştirmek için işbirliğini anlatır. En önemli odak noktası,üretim sisteminin tasarımı ve geliştirme analizidir.Radio frekansı tanıma özelliği ile üretim sistemi kullanarak birleşik modelleme dili diagramları temin eden sistem entegrasyonu ile daha fazla esneklik yaratır,verimli algoritmalar ve etkili araçlar ve radio frekansı tanımlama özelliği ile üretim sistemi mimari uygulamalarını anlatır. Radio frekansı tanımlama özellikli dağıtılmış kontrol etkin ve izleme sistemi başarıyla önerilen mimari uygulanabilirliğini göstermek için esnek bir üretim sistemi (DAÜ-CIM laboratuar) kullanılarak incelenmiştir.
Incorporation of various turbulence models into a flow solver for unstructured grids
[Abstract Not Available]
Mathematical Modeling of Magnetic Regenerator Refrigeration Systems
ABSTRACT: Active magnetic regenerative refrigeration (AMRR) systems are designed based on magnetocaloric effect of some special solid materials, such as Gadolinium-Silicon-Germanium, Ferrum-Rhodium, etc. During the last three decades, a variety of cooling systems have been proposed using magnetic materials at room temperature. In this thesis, an AMRR system using FeRh as refrigerant is studied. For the simulation, a one-dimensional, time-varying mathematical model is developed. This model consists of two energy equations for the heat transfer fluid and the regenerator which are descritized by finite difference method. The simulation begins at an initial temperature distribution in the regenerator and fluid and takes time steps forward in time and space until the steady state is attained. On the other hand, in order to simulate the system, it was necessary to obtain and code the properties of the FeRh alloy, especially the entropy. The entropy of the alloy was calculated by using the specific heat experimental data. The coding procedure of properties was done by surface fitting and additional interpolation. To verify the developed model, the temperature distribution in the regenerator was obtained for all stages using Gadolinium as the refrigerant validated with some published results. At last, the performance of the refrigerator was optimized in terms of refrigerant porosity, mass flow rate, and type of the heat transfer fluid. The capability to give acceptable results of the performance of the system proves that the model is a powerful tool to predict the performance of AMRR systems. Besides, the high performance of the AMRR gained in this study, shows that this upcoming technology will be a suitable alternative for space cooling in the near future. ……………………………………………………………………………………………………………………………………………………………………………………………………………………
Experimental and Numerical investigation of flow structures behind Bluff Bodies in Tandem Arrangement
Flow structures attracted scientist since many decades. When a fluid flows around a bluff body or an object moves within a fluid at different Reynolds numbers different flow regimes can be observed. The flow properties plays great importance in analysis of different applications. These properties either calculated with numerical or experimental techniques. Experimental studies are time consuming and more expensive. Developments in computers enabled scientist to analyse and simulate almost all flow conditions easily. But always these results must be compared with experimental results to have more healty conclusions. In this study flow properties such as instantaneous velocity, normalized velocity and incoherent flow structures analyzed numerically behind two normal flat plates in tandem arrangement at six different gap ratios. Reynolds Stress Model versus Two-Equation Shear Stress Transport model compared effectively for different gap ratios. Also results of double tandem plates and square cylinder were examined. Computational Fluid Dynamics (CFD) codes ANSYS/FLUENT 13.0® was used to simulate the flow around the normal flat plates. The equations of shear stress transport model and Reynolds Stress Model (RSM) were considered as solution techniques. But since, the validity of any theoretical prediction can only be assessed in practice, the comparison was done between numerical data and achieved data from the experiments, for both cases based on literature. The experiments were done on an open type sub-sonic wind tunnel at Reynolds number of 33000 with turbulence intensity around 0.5-0.8%. The effects of gap ratio on the flow characteristics were tested for tandem arrangements. Experimental errors, high cost equipment and spending too much time on testing, result in fulfilling the problem by CFD processes. These numerical methods compared with experimental results to justify the effects of different turbulence model.
Trade-off among Mechanical Properties and Energy Consumption in Multi-pass Friction Stir Processing of Al 7075-T651 Alloy Employing Hybrid Approach of Artificial Neural Network and Genetic Algorithm
ABSTRACT: Friction Stir Processing (FSP) is a solid state and thermomechanical processing technique that modify and improve the microstructural and mechanical properties of the material to achieve better performance in less time, using a simple and inexpensive tool and low production cost. Processed zone contains modified mechanical properties, fine grained, equaled and homogeneous microstructures. Discussions about efficient use of energy and expense have become more frequent in many sectors of industry. During manufacturing processes, power consumption of components and potential for savings can be evaluated and measures can be defined for the efficient use of energy. In the present work, FSP was applied on the Aluminum 7075-T651 alloy sheet. Application of multi-objective multivariable genetic optimization in FSP was presented. A trade-off among various mechanical properties of an aerospace alloy and energy consumed during FSP was sought out. At first, the experimental data regarding the elongation, tensile strength, hardness and the consumed electrical energy with respect to various spindle rotational speed and feed rate of FSP were measured. Then an Artificial Neural Network-based approximation approach was used to approximate the value of measured data during the Genetic Optimization. The properties like elongation, tensile strength and hardness were maximized while the cost of consumed electrical energy was minimized. Keywords: Friction Stir Processing; Al7075; Multi-objective; Genetic Algorithm; Optimization; Artificial Neural Networks. …………………………………………………………………………………………………………………………
Energetic and Exergetic Analysis of a Solar Organic Rankine Cycle with Triple Effect Absorption System
As the population increases, the energy demand increases and this requires to develop new and alternative technologies such as wind, solar, biomass, and geothermal for meeting the demands. There was a significant increase in the study of multi-generation energy systems in the last decades, in order to decrease consumption of non-renewable energy sources and optimize more viable and economical energy production. A multi-generation system is a process used to produce three or more different outputs, such as hydrogen, electricity, cooling, hot water, heating, fresh air and water with the same input energy sources. In this thesis, a new multi-generation energy system is proposed based on solar energy. Solar energy is applied by feeding an Organic Rankine Cycle (ORC) which is then used to supply hot water to the buildings as well as electric current to the electrolyser with the aim of production hydrogen and also using in the building. A triple effect absorption system is utilized to produce cooling, heating, and dry air. A comprehensive thermodynamic analysis is defined, and the effects of various operating conditions and configurations on the output are analyzed. The results show that the system has an exergetic utilization factor of 0.6 and an energetic utilization factor of 2.61 based on generating electricity of 427kW. Also the energetic and exergetic COP of absorption chiller are determined to be 1.16 and 0.24, respectively. In the proposed system, the energetic and exergetic efficiency of Organic Rankine Cycle are 21.08% and 33.98, respectively. The extracted numbers from the system analysis in comparison with previous studies, validate the system performance under the defined initial parameters. So by analyzing the obtained results, it has become a necessity to decrease the system’s irreversibility and increase the energy and exergy efficiencies to reach a high efficient system. All modeling and thermodynamic analysis have been done by Engineering Equation Solver (EES) software. Keywords: Absorption System, Multi-generation System, Energy, Exergy, Efficiency
Design and Development of a Novel Thermochemical Reactor Using Composite Sorbent for Solar Thermal Energy Storage
Thermochemical heat storage (THS) is being considered as a potential technology in order to enhance the utilization of renewable energy sources due to its high energy storage density and long term heat storage capacity. However, further advancement in such systems depends on the development of novel sorption materials and innovative solar-driven thermochemical processes. To this end, this work presents new sorption materials and a new solar-driven THS process suitable for building applications. In the first part of the study, two novel composite sorbents consisting of aerated porous concrete-calcium chloride (APC-CaCl2) and pumice-calcium chloride (P-CaCl2), respectively, were synthesized. Other than the synthesized new composite materials, vermiculite-calcium chloride (V-CaCl2) and zeolite were also selected and synthesized for a comparative performance study. A new experimental scale THS system was designed and developed for investigating the charging/discharging characteristics of all synthesized sorption materials. The experimental results show that, the values of the average energy storage density of the system operating with APC-CaCl2, V-CaCl2, zeolite, and P-CaCl2, for five hours of discharging were 186.9 kWh/m3, 174.2 kWh/m3, 182.6 kWh/m3 and 204.3 kWh/m3, respectively. For a charging temperature of 90 ºC over three hours of charging process, the mass desorption rate of APC-CaCl2 was found to be 9.84 g/min, while, it was 4.40 g/min, 13.27 g/min and 14.13 g/min for zeolite, V-CaCl2 and P-CaCl2, respectively. Considering their charging/discharging performances and their cyclic stability, P-CaCl2 and V-CaCl2 were found to be the best candidate materials for THS applications. In the second part of the study, a solar-driven THS was designed, developed and tested under real climatic conditions of North Cyprus. V-CaCl2 was selected as the working material due to its high energy density, good cyclic ability and the low cost and availability of vermiculite (host matrix) in North Cyprus. Three series of charging-discharging experiments were performed employing the newly developed solar-driven THS system. The discharging tests were performed during the night for a duration of five hours. During the discharging experiments, the temperature and relative humidity of air at the reactor inlet were in the range of 21 – 24 ºC and 80 – 90 %, respectively. Under these conditions, the average energy output over three cycles was found to be 2.1 kWh, with an average energy storage density of 156 kWh/m3. A manufactured parabolic solar concentrator was utilized to provide the required thermal energy in the charging process. Hence, the average surface temperature of the reactor was in the range of 78 ºC to 83 ºC and the average useful energy of the charging process was 3.94 kWh. The rate of moisture desorption was 6.5 g/min while the overall efficiency was 38%. Furthermore, an economic analysis was performed to compare the feasibility of the proposed solar-driven THS system and a typical heat-pump unit of the split air-conditioner under the climatic conditions of North Cyprus. The heating load of a house with an area of 90 m2 was simulated in the DesignBuilder software, and from the simulation results, it was found that a solar-driven THS system with a reactor volume of 8.75 m3 is required to meet 1366 kWh of an annual heating load of the building. The analysis showed that the net present value of THS system after ten years would be $381 with a simple payback period of 6.4 years, which illustrates the economic feasibility of the THS system. Keywords: Thermochemical Heat Storage, Solar Energy, Thermodynamic Analysis, Porous Host Matrix, Calcium Chloride, Composite Sorbent, Experimental
Electricity Peak Demand Forecasting for Developing Countries
The current thesis aims to develop a peak demand forecast model suitable for developing countries based on their characteristic and availability of data. In this respect, we attempted to review a number of techniques used for energy forecasting and categorize them in terms of time ranges, the techniques used, and the cases in which they were employed. The advantages and disadvantages of each method were indicated and suitable approaches were devised to forecast the energy demand for small and large developing countries. We developed two different scenarios for small utilities depending on the availability of time series data. First, when considerable amount of time series data is available we proposed an econometric method to model the annual peak demand by which the key parameters affecting the electricity demand were discovered. The electricity demand was decomposed into weather sensitive demand and based demand to further examine the effect of extreme weather conditions on the peak demand. Second, when time series data is limited to merely annual peak demand records, an algorithm based on deterministic time series methods and fuzzy arithmetic was developed. These methods can be applied to forecast electricity demand of N. Cyprus and similar small islands. Thus, some advices were offered for electricity security plan of N. Cyprus. Finally, using the previously developed forecasting models, an approach was presented to forecast the peak demand of all developing countries based on their distinctive regional characteristic. The algorithm requires partitioning the country into smaller segments in which the previously developed forecast models for small utilities can be utilized. Keywords: Decomposition, Econometric Method, Extension Principle, Fuzzy Arithmetic, Peak Demand Forecasting, Time Series Method, Transformation Method
Experimental Studies on Flow Structures Behind Bluff Bodies and Suppression of Vortex Street
One of the most significant features of flow around bluff bodies is the formation of vortices in the downstream wake. Such unsteady wake could incur unsteady loading where the vortex-induced vibration can have destructive effects on the structure of sky scrapers, cooling towers, chimneys and bridges which civilization relies on. In this study vortex shedding in the wake region of single and dual bluff bodies have been investigated, and possible passive flow control method have been employed to suppress formation of vortex street in the wake region downstream the bluff bodies. In this study the effects of entrainment of fluid through perforated surface on suppression of vortex street behind Perforated Square Cylinder have been studied experimentally. Wake region have been investigated in terms of coherent flow structure, time averaged properties and effectiveness of different perforations. The quantitative measurements revealed that the perforated surfaces are only effective within width interval of y/D= ±1.0. It was observed that in the near wake region up to approximately 1.5D downstream the wake, the shedding phenomenon has been suppressed significantly. It was also demonstrated that velocity profiles and flow structure affected by different perforated surfaces, and as a result coherent structures have been diminished considerably. In addition, interacting wakes of two inclined flat plates in tandem arrangement have been studied experimentally. The effects of gap ratio (g/D) between the plates together with angle of attack (α) on the flow structure in the wake region, incoherent and coherent time averaged properties profiles have been investigated. Different set of experiments have been conducted for gap ratios 0.5 and 1.5 between the plates, replicating single and dual body vortex shedding mode. In addition, various angle of iv attack (45-75 degree) have been studied to probe the effects of inclination on the wake region in terms of shedding frequency and Strouhal number variation. The results revealed that Strouhal number decreases as angle of attack increases. Moreover, increasing gap ratio affects the flow structure and as gap ratio increases, incoherent Turbulent Kinetic Energy production in the downstream wake have been decreased. Keywords: Vortex Shedding, Suppression, incoherent and coherent flow structure, Perforated Square Cylinder, Inclined flat plate, Interacting wake, Tandem arrangement
Design of Integrated Geothermal- Solar Based System for Multigenerational Needs in a District Energy System Application
The current thesis proposes an integrated geothermal based multi-generation system including the triple effect LiBr/water absorption system (TEAS), organic Rankine cycle (ORC), air-conditioning system (dehumidification with cooling) and an electrolyzer. The aim of this system is to supply six outputs comprising heating, cooling, dry air, hot water, hydrogen, and power. All the simulations are done by Engineering Equation Solver software (EES). By inputting 500K geothermal water, the energetic and exergetic overall utilization factors (Ɛen and Ɛex) for the completely multi-generation cycle would be 2.467 and 1.097, respectively. A parametric study was conducted indicating that a rise in the environment (ambient) temperature from 295K to 320K leads to an accumulative trend for exergetic coefficient of performance (COPex) while energetic coefficient of performance (COPen) remains constant in TEAS. While, the evaporator temperature rises from 274K to 279K, there is a downward trend for COPen and COPex (from 1.491 to 1.479 and 0.3525 to 0.3145, respectively) as well as Ɛen and Ɛex. By raising the geothermal temperature from 400K to 500K, Ɛen and Ɛex will increase from 2.354 to 2.467 and from 1.055 to 1.105, respectively. Moreover, the rise in geothermal temperature will upsurge the rate of hydrogen production as well as the heat rate in hot water production from 0.004873L/s to 0.005944L/s and from 8.365kW to 112.9kW, respectively. Moreover, environmental impacts, as one of the most designing parameter, are analyzed to find the system irreversibility (exergy destruction) and exergy losses. The parametric simulation is done to check the system in term of environmental suitability. In addition, a comparative study shows that using multi-generation cycle with higher COPen and COPex in comparison with conventional systems is more feasible to design for reaching the six outputs. Keywords: Geothermal, Multi-generation, Energy, Exergy, Overall Utilization Factor, Exergoenvironmental Impact Factors.
Modeling and Experimental Investigation of Springback in Brass Alloy Sheet Metal V-Bending
One of the most important criteria in a good bending is springback. Springback can be defined as the amount of shape recovered after bending load. Springback value is somehow influenced by some factors like bending force, die opening, bend radius, bend angle, sheet metal thickness and punch holding time, and heat treatment. In this study, springback is investigated in v-bending for yellow brass material (UNS C27000 brass). The investigation of the springback will consider three parameters. The selected parameters to be varying will be the thickness of sheet metal (1.5mm 3mm and 5mm), the die opening (22 and 35mm), and the punch holding time (0 5 and 10 seconds) and all the other parameters will remain constant like the die angle and punch angle (85°). A full factorial multilevel design of experiment (DOE) method is used to conduct the experimental test. Finite element simulation (FEA) using ANSYS IMPLICIT, and experimental investigation results are compared. In addition, machine learning with ANN and SVM methods are used to predict the springback. The analysis of the result done with ANOVA showed interesting facts. The Pareto chart reveals that in comparison with the two other parameters, the sheet thickness has the highest significant effect on the springback and the die opening has the lowest significant effect. In overall the metal behaved approximately like the other metals because the springback decreased when the die opening increased and also when the holding time increased, and also when the sheet thickness increased. However, the brass material went in contradiction with the previous researches on the 3mm sheet thickness. Keywords: springback, finite element analysis (FEA), SVM, ANN, ANOVA.
Configuration Design and Optimization of Circular Automated Storage and Retrieval System (C-AS/RS)
Automated Storage and Retrieval Systems (AS/RS) are used as warehouses, specifically designed for material handling in advanced manufacturing systems and are broadly utilized in distribution centers as subsystem for production area. Previous research efforts on have focused on the design and optimization of rectangular AS/RS configurations, however, there is still a gap of research on the design and optimization of Circular AS/RS Configurations. The aim of the research is to analyze, optimize and propose a Circular AS/RS Configuration for automotive car parking. Recently AS/RS are implemented to the automotive factories due to inventory control, landscape utilization, cost and efficiency. The proposed configuration is based on a single aisle; single S/R (Storage/Retreival) machine. Randomly storage assignment policy is applied for the proposed system. The Cost and Travel time models are adapted from the previous research on AS/RS. A mixed integer multi-objective optimization problem is formulated to be optimized using Genetic Algorithm (GA), which is a non-gradient, direct search metaheuristic optimization method, well suited for this class of problems. The design objectives are to minimize travel time, minimize carbon footprint, and minimize the total cost under the constraints for system height, diameter and storage capacity. The number of rows and columns, vertical, rotational and radial velocities of the S/R machine are taken as the decision variables. The results show that travel time, total cost, and the carbon footprint has been minimized up to 1.05%, 16.31% and 67% respectively. Keywords: Configuration, Design, Automated Storage and Retrieval Systems, Optimization, Travel Time, Total Cost, Carbon Footprint.
Monitoring the Performance of a Small-Scale Wind Turbine
ABSTRACT: Small wind turbines are known to generate less than 100 kW of electricity and they are used in farms, homes and small businesses for backup electricity to reduce electricity bills. The present work is concerned with the monitoring of a small scale wind charger which is mounted on the roof of the building of the department of mechanical engineering at Eastern Mediterranean University. Rutland 913 wind charger used for this work has a swept diameter of 910 mm and produces a power output up to 300Wp. A data acquisition system composed of a microcontroller and a series of resistors are used to measure the current and voltage and calculate the corresponding power and wind speed. Using a serial port, data are sent to a personal computer (PC). The data transferred to the PC are recorded to a text file using a purpose-designed program for this system. Two methods of estimating annual energy output (AEO) are introduced and compared with actual data. Data recorded are displayed as a power versus hour curves for each month. Average wind speed for the period of measurements (7 months) was obtained as 4.9 m/s and power produced at this speed was measured as 12.6W. AEO generated was estimated to be 110kWh/yr according to experimental data. By using the swept area and power curve methods, the theoretical AEO was estimated as 103.2kWh/yr and 112.21kWh/yr respectively. Keywords: Small-scale wind turbine, power output, data acquisition system, microcontroller, annual energy output. ……………………………………………………………………………………………………………………………………………………………………………………………………………………