• Energy Research

An electric arc furnace with a liquid steel capacity of 30 t was analyzed using the second law of thermodynamics. To carry out the exergy analysis, materials and energies entering and exiting the electric arc furnace were determined. The materials included several types of scrap, cokes, fluxes, oxygen, liquid steel, stack gases, and dust. Electrical and exothermic chemical energies of these materials were considered. Energies of the materials leaving the furnace, including liquid steel, slag, stack gases, and dust, were determined, as were the chemical reactions and exergies entering and leaving the electric arc furnace. Exergy efficiency and lost exergy were calculated. It was found that 42.6% of exergy is lost because of the chemical reactions, heat transfer, and other reasons. The overall exergy efficiency of the entire system was found to be 46%.

Energy issues are directly related to the development of a country and the living standards of its people. In this study, Turkey's energy resources, installed electric power capacity, electric energy production and consumption rates are investigated and compared with some other countries. And some comments have been made on the future electric energy production investments. Besides, the potentials of Turkey's energy resources are exposed also Turkey's electric energy production strategy is interpreted.

This study was built on the basis of an experimental study that was carried out on a simple refrigeration system that works with R134a as a refrigerant, and based on the real dimensions of the system and the experimental results, the Ansys fluent software was used to simulate the system to prepare the system to introduce the nanoparticles theoretically. Since the nanoparticles preparation process is expensive, this research presents a simple, easy, and inexpensive method for the preparation process based on the following materials, distilled water, ammonia, copper nitrate, and cerium nitrate to synthesize seven types of nanoparticles as a single oxide and as a mixture from two different oxides The results of preparing using X-Ray Diffraction and Scanning Electron Microscopy proved that particles of samples were spherical in shape, with suitable average diameter ranging between 78.95, 79.9, 44.15 and 63.3 nm for both copper oxide, cerium oxide, first mixture, and second mixture, respectively, the theoretical study confirmed that both copper oxide, cerium oxide, and the mixture consisting of both improved the performance of the refrigeration system and reduced energy consumption.

Abstract This study aims at examining energy and exergy efficiencies in Turkish transportation sector. Unlike the previous studies, historical data is used to investigate the development of efficiencies of 17 years period from 1988 to 2004. The energy consumption values in tons-of-oil equivalent for eight transport modes of four transportation subsectors of the Turkish transportation sector, including hard coal, lignite, oil, and electricity for railways, oil for seaways and airways, and oil and natural gas for highways, are used. The weighted mean energy and exergy efficiencies are calculated for each mode of transport by multiplying weighting factors with efficiency values of that mode. They are then summed up to calculate the weighted mean overall efficiencies for a particular year. Although the energy and exergy efficiencies in Turkish transport sector are slightly improved from 1988 to 2004, the historical pattern is cyclic. The energy efficieny is found to range from 22.16% (2002) to 22.62% (1998 and 2004) with a mean of 22.42±0.14% and exergy efficiency to range from 22.39% (2002) to 22.85% (1998 and 2004) with a mean of 22.65±0.15%. Overall energy and exergy efficiencies of the transport sector consist mostly of energy and exergy efficiencies of the highways subsector in percentages varying from 81.5% in 2004 to 91.7% in 2002. The rest of them are consisted of other subsectors such as railways, seaways, and airways. The overall efficiency patterns are basically controlled by the fuel consumption in airways in spite of this subsector's consisting only a small fraction of total. The major reasons for this are that airways efficiencies and the rate of change in fuel consumption in airways are greater than those of the others. This study shows that airway transportation should be increased to improve the energy and exergy efficiencies of the Turkish transport sectors. However, it should also be noted that no innovations and other advances in transport technologies are included in the calculations. The future studies including such details will certainly help energy analysts and policy makers more than our study.

Chemical exergy is equal to the maximum amount of work obtainable when the substance is brought from the environmental state to the dead state by a process involving heat transfer and exchange of substances only with the environment. As it is well known the iron and steel industry is the largest industrial energy consumer. After the employee costs, energy costs (about 30% of the total) represent the second highest cost element in integrated steel works. In this study, the chemical exergy potential in an electric arc furnace (EAF) is calculated and these potentials are distributed depending on production materials, emphasizing the chemical exergy concept.

Abstract The purpose of this study is to present the numerical modeling techniques for a Ground Source Heat Pump (GSHP): The Bolu case. Numerical modeling of the GSHP system with horizontal ground heat exchangers operating in heating (1.4 kW) mode was carried out for a room, with 9.68 m2 floor area, located in Bolu, Turkey. The GSHP simulation model is studied. The codes are written in the MATLAB program for solving the equations obtained from the model developed for the city of Bolu. In this program, additionally, state equations of cooling fluids, which calculate the thermodynamic properties of these fluids, are required. In literature, there are only state equations depending on many coefficients for R12, R22, and R502. So, state equations and table values of ASHRAE of R12, R22, and R502 are used in order to obtain the properties of R134a, R404a, and R410a by using the curve fitting method. The results show that COP values for R134a refrigerant are 3.33 and 3.28 for MATLAB program and Solkane Refrigerant Software program, respectively. The difference on COP was 0.05, i.e. approximately 1.52%. The results obtained from MATLAB program indicate that there was good agreement between Solkane Refrigerant Software program and MATLAB program.

AbstractThis paper addresses the problem of optimal placement of wind turbines in a farm on Gokçeada Island located at the north‐east of Aegean Sea bearing full potential of wind energy generation. A multi‐objective genetic algorithm approach is employed to obtain optimal placement of wind turbines by maximizing the power production capacity while constraining the budget of installed turbines. Considering the speed and direction history, wind with constant intensity from a single direction is used during optimization. This study is based on wake deficit model mainly because of its simplicity, accuracy and fast calculation time. The individuals of the Pareto optimal solution set are evaluated with respect to various criteria, and the best configurations are presented. In addition to best placement layouts, results include objective function values, total power output, cost and number of turbines for each configuration. Copyright © 2009 John Wiley & Sons, Ltd.

The production of steel of desired composition is realized as a result of bringing some of the elements to the desired amounts after a series of chemical reactions occurring at different velocities between the elements or compounds at high temperatures and adding alloy materials for the other elements needed in the composition. The steel production process in an electric arc furnace can be defined in the following order: scrap charge, melting, oxidation, reduction, alloying, deoxidization, casting, and preparation of the furnace. In this study, a mass analysis is accomplished for an electric arc furnace at a steel company in Turkey. In order to make the mass balance, firstly all materials that are entering the system are calculated on a chemical component basis. The necessary information was provided from an iron and steel producing company. The results of the mass analysis are presented at the end of the study.

In this study, exothermic and endothermic chemical reactions are determined for an electric arc furnace (EAF) and a ladle furnace, and their chemical energies are calculated taking account of input and output materials from the EAF.