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Öğe Magnetite nanoparticles grafted with murexide-terminated polyamidoamine dendrimers for removal of lead (II) from aqueous solution: synthesis, characterization, adsorption and antimicrobial activity studies(Journals & Books, 2021-03) Ekinci, Selma; İlter, Zülfiye; Ercan, Selami; Çınar, Ercan; Çakmak, ReşitIn this study, new, efficient, eco-friendly and magnetically separable nanoadsorbents, MNPs-G1-Mu and MNPs-G2-Mu, were successfully prepared by covalently grafting murexide-terminated polyamidoamine dendrimers on 3-aminopropyl functionalized silica-coated magnetite nanoparticles, and used for rapid removal of lead (II) from aqueous medium. After each adsorption process, the supernatant was successfully acquired from reaction mixture by the magnetic separation, and then analyzed by employing ICP-OES. Chemical and physical characterizations of new nanomaterials were confirmed by XRD, FT-IR, SEM, TEM, and VSM. Maximum adsorption capacities (qm) of both prepared new nanostructured adsorbents were compared with each other and also with some other adsorbents. The kinetic data were appraised by using pseudo-first-order and pseudo-second-order kinetic models. Adsorption isotherms were found to be suitable with both Langmuir and Freundlich isotherm linear equations. The maximum adsorption capacities for MNPs-G1-Mu and MNPs-G2-Mu were calculated as 208.33 mg g−1 and 232.56 mg g−1, respectively. Antimicrobial activities of nanoparticles were also examined against various microorganisms by using microdilution method. It was determined that MNPs-G1-Mu, MNPs-G2-Mu and lead (II) adsorbed MNPs-G2-Mu showed good antimicrobial activity against S. aureus ATTC 29213 and C. Parapsilosis ATTC 22019. MNPs-G1-Mu also showed antimicrobial activity against C. albicans ATTC 10231.Öğe Thermal performance enhancement of flat-plate solar collectors by means of three different nanofluids(Elsevier, 2018-12) Budak Ziyadanoğulları, Neşe; Yıldız, Cengiz; Yücel, Halit LutfiSolar energy, which comes first among renewable energy sources, enables efficient use of energy with many applications due to its low operating cost and environmental friendliness. In this study, we experimentally investigated the effects on thermal efficiency of nanofluid and water as working fluids in flat-plate solar collector hot water solar energy systems. Nanofluids were prepared by adding Al2O3, CuO, and TiO2 nanoparticles at 0.2, 0.4, and 0.8 vol% into distilled water, and then the thermophysical properties (thermal conductivity, viscosity) of the prepared nanofluids were determined. Flow rate was adjusted to 250 l/h at given concentrations for each nanofluid in the experimental setups and data such as collector inlet and outlet temperatures, ambient and tap water temperatures; radiation, humidity, and wind speed were measured and recorded. The obtained data were used to calculate efficiencies according to ASHRAE 93-2003 standards. When compared with water, the results indicated that the use of nanofluid increased collector efficiency.Öğe Microstructure and mechanical properties of armor 500/AISI2205 steel joint by friction welding(Journals & Books, 2017-08) Batı, Serkan; Kırık, İhsan; Sarsılmaz, FurkanThis paper discussed the properties of friction welded joint of Armor 500 steel and duplex (ferritic/austenitic) steel AISI 2205 and compared the properties of weld at different welding parameters. The experimental study was conducted with the welding parameters such as friction pressure and friction time. The experimental results indicated that armor 500 steel could be joined to AISI 2205 steel using the traditional friction welding technique. The processed joints were tested through axial tension test. In addition, the highest tensile strength, which is 1020 MPa is obtained when friction time is 8 s and friction pressure is 80 MPa. The microstructures of the alloys and fracture surfaces were examined by optical and scanning electron microscopy. Experimental results indicate that microstructural and mechanical properties are significantly affected by changing welding parameters within the chosen range of conditions.Öğe Heat transfer and exergy loss in conical spring turbulators(Elsevier, 2013-05) Karakaya, Hakan; Durmuş, AydınIt would be misleading to consider only the construction costs of heat exchangers in their design because high service costs during their service life may also greatly increase total costs. Therefore energy saving aspects are very important in the design, construction and operation of the heat exchangers. For this reason, various active or passive methods have been sought to save energy by increasing the heat transfer coefficients in the cold and warm fluid sides in the heat exchangers. Conical spring turbulators (CST) are devised in this study. Performances of heat transfer and pressure drop in a pipe with the CST are experimentally examined for the CSTs’ angle (θ) of 30°, 45° and 60° in Reynolds number (Re) range of 10,000–34,000. Heat transfer, pressure loss and exergy analysis were made for the conditions with and without turbulators and compared to each other. Some empirical correlations expressing the results were also derived and discussed.Öğe Investigation of effects of cutting insert rake face forms on surface integrity(SpringerLink, 2017-06) Gürbüz, Hüseyin; Şeker, Ulvi; Kafkas, FıratIn this study, the effects of cutting insert rake face forms and cutting parameters on the surface integrity in machining of AISI 316 L steel were investigated experimentally. The cutting forces occur during chip removal, surface roughness values on the machined surfaces with residual stresses on machined workpiece were measured, and metallurgical structure (microhardness and microstructural variations) of the surface layers formed as a result of machining were evaluated. The surface integrity was evaluated in terms of surface roughness, residual stress, microhardness, and microstructure analysis. In experiments, the best surface integrity results were obtained by cutting tools having QM form, and the worst surface integrity results were obtained by cutting tools having MR form. Under all these cutting conditions, it was observed that the surface integrity worsened when depth of cut and cutting feed were increased; however, the surface integrity improved when cutting speed was increased. In terms of cutting parameters, the best surface integrity was obtained with cutting speed 200 m/min, cutting feed 0.1 mm/rev, and depth of cut 1.25 mm; on the other hand, the worst surface integrity was obtained with cutting speed 125 m/min, cutting feed 0.3 mm/rev, and depth of cut 2.5 mm.Öğe Comparative experimental investigation on the effects of heavy alcohols- safflower biodiesel blends on combustion, performance and emissions in a power generator diesel engine(Elsevier, 2021-02-05) Işık, Mehmet ZerrakkiThe experimental works carried out in this article evaluates the potential of using heavy alcohol and safflower biodiesel as the blended fuel mixtures without making any modifications in the tests diesel engine. For this purpose, volumetrically 20% of Propanol, Pentanol, Butanol, and Octanol were blended with safflower biodiesel fuel and they were named as PR20, PE20, BU20, and OC20, respectively. The performance, combustion, and emission data were found out at the same conditions of constant engine speed and various loads and compared with pure biodiesel (B100) and diesel fuel(ULSD). In the experiments, a four-cylinder, water-cooled diesel engine that was loaded by an electrical power generator was used for the tests. The addition of alcohol causes an increase in fuel consumption due to a decrease in lower thermal performance. The use of heavy alcohols in diesel engine in specific quantities by mixing with biodiesel significantly increases engine brake thermal efficiency. Negative effects of low cetane number and high latent heat of vaporization that may decrease ignition delay and decrease cylinder pressure while increase peak heat release was considered to be compensated by the better mixing properties and atomization of alcohol blended biodiesel thus eventually improve the combustion. Alcohol addition to biodiesel fuel can be accepted as a useful application to increase brake thermal efficiency and reduce nitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbon (HC) emissions by reducing the density and viscosity.Öğe Development of a novel amide silica stationary phase for the reversed phase HPLC separation of different classes of phytohormones(Journals & Books, 2013-05-14) Aral, Tarık; Aral, Hayriye; Ziyadanoğulları, Berrin; Ziyadanoğulları, RecepA novel amide-bonded silica stationary phase was prepared starting fromN-Boc-phenylalanine, cyclo-hexylamine and spherical silica gel (4mm, 60 Å). The amide ligand was synthesised with high yield. Theresulting amide bonded stationary phase was characterised by SEM, IR and elemental analysis. Theresulting selector bearing a polar amide group is used for the reversed-phase chromatography separationof different classes of thirteen phytohormones (plant hormones). The chromatographic behaviours ofthese analytes on the amide-silica stationary phase were compared with those of RP-C18 column undersame conditions. The effects of different separation conditions, such as mobile phase, pH value,flow rateand temperature, on the separation and retention behaviours of the 13 phytohormones in this systemwere studied. The optimum separation was achieved using reversed-phase HPLC gradient elution with anaqueous mobile phase containing pH¼6.85 potassium phosphate buffer (20 mM) and acetonitrile with a221C column temperature. Under these experimental conditions, the 12 phytohormones could beseparated and detected at 230 or 270 nm within 26 minÖğe Production of mixed rare earth oxide powder from a thorium containing complex Bastnasite ore(Journals & Books, 2021-02) Özsaraç, Şafak; Kurşunoğlu, Sait; Hussaini, Shokrullah; Top, Soner; Ichlas, Zela Tanlega; Gökçen, Hasan Serkan; Kaya, MuammerThe production of mixed rare earth oxide powder from a thorium containing bastnasite ore by sulfuric acid bake-water leaching followed by precipitation with oxalic acid and thermal decomposition of the oxalates was investigated. The sulfuric acid baking was performed at 250 °C and the optimum baking time was found to be 3 h. Using deionized water as lixiviant, 92.6% La, 86.8% Ce, 86.9% Pr, 82.3% Nd, 95.4% Th and 31% Y were dissolved from the baked ore at 25 °C after 30 min of leaching. The effect of solid-to-liquid ratio on the dissolution of the rare earth elements and thorium shows that when the solid ratio in the water increased from 1:10 to 1:3, the dissolution percentage decreased. The final mixed rare earth oxide powder contained 88.54% REO and 6% ThO2 together with small amounts of other impurities. The SEM mapping results revealed that the produced REO has an irregular crystal shape. Based on the experimental results obtained from the current study, a flowsheet was proposed for the production of mixed rare earth oxide powder from a specific complex bastnasite ore.Öğe Drying of sweet basil with solar air collectors(Elsevier, 2016-08) Karakaya, Hakan; Durmuş, Aydın; Fevzi, GülçimenIn this study, sweet basil was dried and its drying parameters were investigated experimentally and theoretically by using newly developed solar air collectors. Proper temperatures were chosen to dry sweet basil and experiments were carried out at different flow rates. At the end of drying experiments, it was determined that total mass of sweet basil decreased from 0.250 kg to 0.029 kg. In drying sweet basil, dimensionless moisture ratios were decreased rapidly to 300 min for 0.012 kg/s, 360 min for 0.026 kg/s, and 450 min for 0.033 kg/s. It was observed that the efficiency of collector was increased at the same rate with air flow changed between 29 and 63%. Among the models in the literature, Page Model was found to suit best for drying sweet basil. Furthermore, a novel mathematical model rendering more valid results for sweet basil and leafy products was developed.Öğe Experimental and numerical investigation of the effect of turbulator on heat transfer in a concentric-type heat exchanger(Taylor & Francis, 2015-05-21) Budak Ziyadanoğulları, Neşe; Argunhan, Zeki; Yücel, Halit LutfiThis article experimentally and numerically analyzes the effect of turbulators with different geometries (Type I, Type II, Type III, and Type IV) located at the inlet of the inner pipe in a concentric-type heat exchanger. Experiments were performed at parallel-flow conditions in the same and opposite directions to investigate the impact of manufactured turbulators on heat transfer and pressure drop. In the numerical study, ANSYS 12.0 Fluent code program was used, and basic protection equations were solved in the steady-state, three-dimensional, and turbulence-flow conditions. Results were obtained from numerical analysis conducted at different flow values of air (7, 8, 9, 10, 11, and 12 m3 /h). The distribution of temperature, velocity, and pressure was demonstrated as a result of numerical analyses. Experimental and numerical results were compared, and it was observed that they were in conformity with each other. When the data obtained from the analyses were examined, the highest heat transfer, pressure drop, and friction factor increase were detected to be in the Type IV turbulator.
