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Ac ikkalp E.,Bilecik University | Caner N.,Eskiehir Osmangazi University
Physica A: Statistical Mechanics and its Applications | Year: 2015

In last decades, nano technology developed. Since, nano scale thermal cycles will be possibly used in near future. In this study, a nano scale irreversible dual cycle was analyzed thermodynamically. Ideal Maxwell-Boltzmann gas is used for working fluid in the system. He4 is chosen as working fluid. Results are obtained as numerically. In calculations, different thermodynamic performance evaluation methods are applied and these methods are compared each other to determine the most convenient optimization way. © 2015 Elsevier B.V. All rights reserved.


Kesler M.,Bilecik University | Ozdemir E.,Kocaeli University
IEEE Transactions on Industrial Electronics | Year: 2011

This paper presents a new synchronous-reference-frame (SRF)-based control method to compensate power-quality (PQ) problems through a three-phase four-wire unified PQ conditioner (UPQC) under unbalanced and distorted load conditions. The proposed UPQC system can improve the power quality at the point of common coupling on power distribution systems under unbalanced and distorted load conditions. The simulation results based on Matlab/Simulink are discussed in detail to support the SRF-based control method presented in this paper. The proposed approach is also validated through experimental study with the UPQC hardware prototype. © 2010 IEEE.


Koc C.,Bilecik University
Renewable and Sustainable Energy Reviews | Year: 2014

In this study, the development of energy demand in Turkey, the utilization of hydropower potential as well as the problems related to the operation, construction and development phases of hydropower plants have been examined. The number of hydropower plants, their overall installed power (MW), their annual energy production capacity (GWh/yr) and their technical hydropower potential utilization rations have been calculated for the hydropower plants existing in the 25 hydrological basins located in Turkey. The total installed power for hydropower plants under operation for the basins examined in the year 2012 has been calculated as 16,926.80 MW. When the technical hydropower energy potential is taken into account, 28% of hydropower plants are under operation, 27% of them are under construction and 22.4% are under development. In all of the basins, if all of the 1776 projects which are under operation, construction and development are examined, then the total installed power will be 48,298.20 MW, and the annual hydropower production will be 167,333.30 GWh/yr. Hence, as a result, the 77.33% of the technical potential will be utilized. In addition, environmental effects of hydropower plants in the operation and construction phases have been researched. © 2014 Elsevier Ltd.


Acikgoz C.,Bilecik University
Renewable Energy | Year: 2011

Utilization of renewable energy sources and the application of environmentally sound energy technologies are essential to sustainable development and will help to secure the quality of living and the well-being of the future generations. Turkey presently has considerable renewable energy sources. The most important renewable sources are hydropower, wind, solar, geothermal, and biomass. The use of renewable energy as a topic to study energy and its forms permits a novel way to motivate students, particularly those who energy topics taking conscience with the environment. This paper presents the analysis and classification of renewable energy sources and how to find out their origin and a way to motivate students in energy topics related to renewable sources and also, the development of didactic competencies in special blended learning arrangements for educationalists, trainers and lecturers in adult education in the field of renewable energies in Turkey. © 2010 Elsevier Ltd.


Acikkalp E.,Bilecik University
Physica A: Statistical Mechanics and its Applications | Year: 2015

Purpose of this paper is to assess irreversible refrigeration cycle by using exergetic sustainability index. In literature, there is no application of exergetic sustainability index for the refrigerators and, indeed, this index has not been derived for refrigerators. In this study, exergetic sustainability indicator is presented for the refrigeration cycle and its relationships with other thermodynamics parameters including COP, exergy efficiency, cooling load, exergy destruction, ecological function and work input are investigated. Calculations are conducted for endoreversible and reversible cycles and then results obtained from the ecological function are compared. It is found that exergy efficiency, exergetic sustainable index reduce 47.595% and 59.689% and rising at the COP is 99.888% is obtained for endoreversible cycle. Similarly, exergy efficiency and exergetic sustainability index reduce 90.163% and 93.711% and rising of the COP is equal to 99.362%. © 2015 Elsevier B.V. All rights reserved.


Acikkalp E.,Bilecik University
International Journal of Electrical Power and Energy Systems | Year: 2015

In this study, thermodynamic optimization criteria used for assessing thermal engines are investigated and compared. The Purpose of this is to determine the most advantageous criteria. An irreversible Carnot cycle is analyzed by using five different methods and results are compared. According to calculations, the ecological function criterion (ECF) is defined as the most convenient optimization method. Although, its work output is less than the maximum work criteria and maximum available work (MAW), it has advantageous in terms of entropy generation and first law efficiency. In addition, ecological coefficient of performance (ECOP) and exergetic performance criteria (EPC) values provide minimum entropy generation and maximum efficiency at their maximum, however, their work output is very small. ECF obtains its maximum values at x = 0.488 (377.175 kW) for endoreversible cycle and at x = 0.477 (329.812 kW) for irreversible cycle. For these reasons, ECF is suggested as the best optimization criteria. © 2015 Elsevier B.V. All rights reserved.


Acikkalp E.,Bilecik University
Thermal Science | Year: 2013

In this study, the ecological optimization point of irreversible thermal cycles (refrigerator, heat pump, and power cycles) was investigated. The importance of ecological optimization is to propose a way to use fuels and energy source more efficiently because of an increasing energy need and environmental pollution. It provides this by maximizing obtained (or minimizing supplied) work and minimizing entropy generation for irreversible (actual) thermal cycles. In this research, ecological optimization was defined for all basic irreversible thermal cycles, by using the first and second laws of thermodynamics. Finally, the ecological optimization was defined in thermodynamic cycles and results were given to show the effects of the cycles' ecological optimization point, efficiency, coefficient of performance, and power output (or input), and exergy destruction.


Because of the energy needs of the world and the issues involved with global warming, analyzing and optimizing power cycles have increased in importance. In this paper, the concepts of entransy dissipation, entropy generation, power output, exergy output, energy, exergy efficiencies for irreversible heat engine cycles and entransy dissipation, entropy generation, power inputs, exergy input, entropy generation, COP and the exergy of efficiency for the irreversible refrigeration cycle are applied as a means of analyzing them. The results are obtained numerically, and the optimum or critical values are determined for a dimensionless temperature ratio and a dimensionless heat conductance ratio. Finally, recommendations on the design and range of operating conditions for the cycles are presented. Values of TC/TE (x), can be selected between 0.5 and 0.55 and values of kE/k C (y) in the range of 0.3-0.5 can be selected for high performance and low losses in a heat engine. Choosing values of TC/TE (x) and kC/kE (y) as low as possible for high performance, besides low thermodynamic losses (entropy generation and entransy dissipation) for the refrigeration cycle. © 2014 Elsevier Ltd. All rights reserved.


An irreversible heat pump was investigated via entransy analysis and performance criteria. In the analyses, two different convective heat transfer laws were applied to the considered system: the Newton and Dulong-Petit heat transfer laws. The irreversibilities in the system are the result of a finite heat transfer rate, a heat leak and internal irreversibilities, including friction, turbulence etc. In this study, a thermodynamic analysis was performed in detail, and the numerical solutions were used for the conducted analysis. The maximum entransy dissipation (critical points) ranges from 18436.7 kW K to 18855.3 kW K according to y for Newton's law; however, there is no maximum point for the Dulon-Petit law. It can be concluded from this study that entransy should be used among the basic thermodynamic criteria. © 2014 Elsevier Ltd. All rights reserved.


Akyuz B.,Bilecik University
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2013

Influence of Al content on the machinability of AZ series cast Mg alloys was investigated. In order to evaluate the machinability of the alloys, measurements of the cutting forces during turning operations and surface roughness were carried out as well as considering the microstructure and tensile properties. The results show that maximum tensile properties are observed with 2% (mass fraction) Al addition to Mg. As the Al content of the alloy increases above 2%, the cutting forces tend to reduce along with the ductility owing to the grain boundary precipitation of intermetallic phase (β-Mg 17Al12). Cutting forces are able to increase as the cutting speed increases for all the alloys studied, and it's attributed to flank built up at the tip of the cutting tool during machining. © 2013 The Nonferrous Metals Society of China.

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