Situation of Turkey's energy indicators among the EU member states

As a candidate country for EU accession, Turkey should make significant future plans about strategy of consumption and production of basic energy sources. The main goal of this study is determination of energy indicators situation for Turkey—to allow us to draw up a good energy policy for the future using the method of multiple variables data analysis. Basic energy and economic indicators, such as gross generation, installed capacity, net energy consumption per person, import, export, consumption of coal, lignite, fuel oil, natural gas and hydroelectricity are used in the analysis. Energy indicators used in the analysis are taken from the EUROSTAT and Turkish Statistical Institute (TURKSTAT). Results of analysis show that Turkey's most important goal for the future is to produce proper energy policies.     

Large eddy simulation of flow around two side-by-side spheres

Large eddy simulation, using a dynamic Smagorinsky sub-grid scale, is used for the prediction of flow structures around two identical spheres fixed side-by-side at a subcritical flow regime with the Reynolds number equal to 5,000. The QUICK discretization method is applied to discretize the convection terms of the Navier-Stokes equation by means of the finite volume approach. This work focuses mainly on the wake structures downstream of the two interactive spheres located at three various dimensionless separation distances between spheres such as G/D = 1.50, 2.00, and 3.00. The obtained results revealed that the interaction between wakes affects the flow structures downstream of spheres. The rate of this interaction is strongly altered as a function of separation distance. On the other hand, some flow data such as mean drag and mean lift coefficients are affected due to the wake interactions. Finally, examination of the Reynolds stress variation along the different lateral axis, L/D, revealed that the nozzle effect does not play a significant role on the turbulence characteristics beyond the G/D = 3.00.     

APPLICATION OF OPTIMAL CONTROL THEORY IN PIPE INSULATION

Optimum insulation thickness of a pipe subjected to convective heat transfer that minimizes the heat loss is studied using the control theory approach and steepest descent method. As a constraint to the problem, the amount of insulation material is assumed to be fixed. A circular pipe through which fluid is transported from one end to the other is considered. Variations of the bulk temperature of the fluid as well as the temperatures of the outer surface of the insulation are evaluated. It is shown that obtaining an optimal thickness variation of insulation that minimizes the heat losses to the ambient using control theory can be done in a systematic manner. The method can be extended easily to more complex and nonlinear problems.     

Experimental investigation for optimization of design parameters in a rectangular duct with plate-fins heat exchanger by Taguchi method

This study presents the determination of optimum values of the design parameters in a heat exchanger with a rectangular duct by using Taguchi method. The heat exchanger has plate-fins containing periodically interrupted diverging and converging channel flow domains. The experimental investigation for the established heat exchanger involves short rectangular fins attached in 8 × 8 arrays to a surface having various inclination angles. The effects of the six design parameters such as the ratio of the duct channel width to height, the ratio of the winglets length to the duct channel length, inclination angles of winglets, Reynolds number, flow velocity and pressure drop are investigated. In the Taguchi experimental design method, Nusselt number and friction factor are considered as performance parameters. An L₂₅ (5⁶) orthogonal array is chosen as an experimental plan for the design parameters. The analysis of Taguchi method conducted with an optimization process to reach minimum pressure drop (friction factor) and maximum heat transfer (Nusselt number) for the designed heat exchanger. Experimental results validated the suitability of the proposed approach.     

A hybrid multi-fidelity approach to the optimal design of warm forming processes using a knowledge-based artificial neural network

In this paper, a hybrid multi-fidelity optimization approach based on a knowledge-based artificial neural network (KBNN) was used to determine the optimal heating strategy in warm forming processes. First, a less costly, but less accurate isothermal finite element analysis (FEA), which neglected the complex heat transfer between the part and tooling elements, was performed to obtain overall knowledge about the effect of temperature on forming performance. Then, a small number of more accurate and expensive (i.e., longer computational time) non-isothermal FEA results were utilized in an artificial neural network (ANN), along with the prior knowledge from the isothermal FEA, to improve the accuracy in defining the non-linear relationship between the design variables (i.e., regional temperatures on the tooling) and the response (i.e., part depth value before failure). The accuracy of the non-isothermal FEA was validated by comparing its prediction results to the experimental findings. This approach was demonstrated for forming a rectangular cup, where it offered a rapid and accurate recommendation of the optimal temperature distribution on the tooling elements for improved formability. The individual and interaction effects of the regional temperatures on formability were also evaluated in detail by constructing the response surfaces near the optimal design point using the multi-fidelity system developed. Finally, a comparison of the temperature and thickness strain distributions on the formed parts was made under various operating conditions, to acquire detailed information on the deformation characteristics of the material.     

Investigation of correlations between shear wave velocities and CPT data: a case study at Eskisehir in Turkey

Seismic waves result from fault movement during earthquakes. Depending on the features of the physical environment through which they pass, there are variations in the velocity and amplitude of body waves, which occur underground, and surface waves, which occur on the Earth’s surface. The ratio of shear wave velocity (V _s) to near-surface velocity is a parameter used widely in land use planning to predict the potential for amplified seismic shaking, especially in urban areas. The main objective of this study was to estimate V _s by using cone resistance (q _c) and lateral friction (f _s) for a study area at Eskisehir Graben, to help mitigate geotechnical earthquake engineering problems in civil engineering and land use planning. In geotechnical shallow soil research, certain geophysical methods are used for measuring V _s —a major form of seismic energy propagation—at the near surface. In this study, cone penetrometer data collected from seismic cone penetration tests (SCPT) includes q _c, f _s, and downhole V _s. S-type seismic energy waveforms, which are produced on the surface, were measured at different depths using an S-type geophone in the city center of Eskisehir via SCPT. With SCPT, q _c, friction ratios (R _f), and V _s values were measured at 42 different test points. R _f properties are associated with soil thickness, and these were compared with dynamic soil properties (V _s) using a standard statistical method; we calculated correlations amongst V _s, q _c, and R _f measured from cone penetration tests.     

Second law analysis and heat transfer in a cross-flow heat exchanger with a new winglet-type vortex generator

In this paper a second law analysis of a cross-flow heat exchanger (HX) is studied in the presence of a balance between the entropy generation due to heat transfer and fluid friction. The entropy generation in a cross-flow HX with a new winglet-type convergent–divergent longitudinal vortex generator (CDLVG) is investigated. Optimization of HX channel geometry and effect of design parameters regarding the overall system performance are presented. For the HX flow lengths and CDLVGs the optimization model was developed on the basis of the entropy generation minimization (EGM). It was found that increasing the cross-flow fluid velocity enhances the heat transfer rate and reduces the heat transfer irreversibility. The test results demonstrate that the CDLVGs are potential candidate procedure to improve the disorderly mixing in channel flows of the cross-flow type HX for large values of the Reynolds number.     

Comparing of the Magnetic Force Parameters of Superconducting Maglev System Using Horizontal and Vertical PMG Geometry in Multi-Surface HTS-PMG Arrangement

Journal of Superconductivity and Novel Magnetism - In this study, a detailed static and dynamic experimental studies were carried out in different cooling heights (CH) by using two different...     

Contact resistance characteristics of coated metallic bipolar plates for PEM fuel cells – investigations on the effect of manufacturing

The main purpose of this study is to understand the interfacial contact resistance (ICR) characteristics of coated metallic bipolar plates (BPP) manufactured through stamping and hydroforming. To this goal, 51 μm thick SS316L stainless steel sheet blanks were formed into BPPs using two forming techniques (stamping and hydroforming); then these formed plates were coated with three different PVD coatings (CrN, TiN, ZrN) at three different coating thicknesses (0.1, 0.5 and 1 μm). Contact resistance of the formed and coated BPP samples were measured before and after they were exposed to the proton exchange membrane fuel cells (PEMFC) operating conditions (i.e., corrosive environment). ICR tests indicated that CrN coating increased the contact resistance of the samples, unexpectedly. TiN samples showed the best performance in terms of low ICR; however, their ICR dramatically increased after short-term exposure to corrosion. ZrN coating, as well, improved conductivity of the SS316L BPP samples and demonstrated similar ICR performance before and after exposure to corrosion.