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Öğe An exergy analysis of a concentric tube heat exchanger using hBN-water nanofluids(Inder Science Publishers, 2021) Budak Ziyadanoğulları, Neşe; Perçin, SüleymanThis study investigated the effects of using nanofluids prepared with hexagonal boron nitride (hBN) nanoparticles on the thermal performance and pressure drop of a concentric tube heat exchanger. Experiments were carried out with water-hBN nanofluids for stable, dispersed, 0.01%, 0.1% and 1% volume concentrations, at different flow rates and Reynolds numbers under parallel and counter-flow conditions. When the experimental results were examined, the exergy loss was higher in the parallel-flow heat exchanger compared to the counter-flow heat exchanger. The highest exergy loss value was obtained for distilled water at the highest Reynolds number (Re = 8,700) for parallel flow operation at 170 W. The exergy loss of water at the highest Reynolds number (Re = 8,700) for parallel flow operation increased by 15.7%, 24.8% and 49.8% for hBN-water concentrations of 0.01%, 0.1% and 1%, respectively. Exergy loss of water at the highest Reynold number (Re = 8,700) for counter flow operation increased by 11.3%, 17.3% and 29.2% for hBN-water concentrations of 0.01%, 0.1% and 1%, respectively. When evaluating the exergy analysis of the system, exergy losses due to pressure drops were negligible for both flows (parallel and counter).Öğe Hardness and wear behaviours of al matrix composites and hybrid composites reinforced with B 4 C and SiC(Springer Nature, 2019-01-15) Çelik, Yahya Hışman; Kılıçkap, ErolThe conversion into the desired shape of the metal powders using Powder Metallurgy (PM) method enables economically mass productions. This case allows producing parts with complex and high dimensional accuracy with no machining. In this study the composites and hybrid composites with Al matrix were produced using PM method with different ratios B4C and SiC. Microhardness and wear experiments of the produced composites were investigated. Wear experiments were performed at a constant speed of 0.5 m/s, application loads of 5, 10 and 15 N and sliding distances of 250, 500, and 750 m. Then, SEM images of composites and hybrid composites were captured. The increase of the reinforcement ratio in the composites contributed to the increase of the hardness. The highest hardness value was computed as 58.7 HV from 16% B4C reinforced composite. In addition, the increase in the reinforcement ratio contributed to the increase of the wear resistance. The increase in the load and sliding distance also increased the wear. The minimum weight loss was calculated as 18 mg from 5 N load, 250 m sliding distance and 16% SiC reinforced composite.Öğe Finite element analysis of the stress distributions in peri-implant bone in modified and standard-threaded dental implants(Taylor & Francis, 2016-01) Topkaya, Tolga; Dündar, Serkan; Solmaz, Murat Yavuz; Yaman, Ferhan; Atalay, Yusuf; Saybak, Arif; Asutay, Fatih; Çakmak, ÖmerThe aim of this study was to examine the stress distributions with three different loads in two different geometric and threaded types of dental implants by finite element analysis. For this purpose, two different implant models, Nobel Replace and Nobel Active (Nobel Biocare, Zurich, Switzerland), which are currently used in clinical cases, were constructed by using ANSYS Workbench 12.1. The stress distributions on components of the implant system under three different static loadings were analysed for the two models. The maximum stress values that occurred in all components were observed in FIII (300 N). The maximum stress values occurred in FIII (300 N) when the Nobel Replace implant is used, whereas the lowest ones, in the case of FI (150 N) loading in the Nobel Active implant. In all models, the maximum tensions were observed to be in the neck region of the implants. Increasing the connection between the implant and the bone surface may allow more uniform distribution of the forces of the dental implant and may protect the bone around the implant. Thus, the implant could remain in the mouth for longer periods. Variable-thread tapered implants can increase the implant and bone contact.Öğe Experimental investigation of solar stills integrated with solar water heating collectors(Türk Isı Bilimi ve Tekniği Derneği, 2017-10-31) Argunhan, Zeki; El, Emin; Yıldız, Cengiz; Çakmak, GülşahSolar still is a more practical way of obtaining clean water. In this study, we aimed to improve the efficiency of solar still systems and obtain distilled water at the same time. For this purpose, 5 different solar still systems were designed. Type 1; conventional solar still, Type 2; conventional solar still integrated with solar water heating collector and run via natural convection, Type 3; conventional solar still integrated with solar water heating collector and tubular heat exchanger and run via natural convection, Type 4; conventional solar still placed with plate heat exchanger and integrated with solar water heating collector and run via natural convection, Type 5; conventional solar still placed with plate heat exchanger and integrated with solar water heating collector and run via forced convection. In this study, the experiments were carried out on the parameters influencing the performance, the amount of distilled water obtained, and the efficiency of experiment settings designed in different types; and finally the results were presented. The amount of distilled water and efficiency of conventional solar still were 2389 ml and 51.47%, respectively. Maximum total amount of water and efficiency from natural convection systems were obtained from Type 4, and the values calculated were found as to be 5788 ml and 55.91%. Maximum amount of distilled water and the efficiency were obtained by utilizing forced convection system were found as to be 6068 ml and 58.99%, respectively.Öğe Investigation of the effect of different variables on strength of adhesive joints(WILEY, 2014-10-01) Adin, Hamit; Deniz, Mehmet EminIn this article, the tensile strength of different adhesive bonded joints under a tensile load was analyzed numerically. The effects of certain parameters, including the bonding length and bonding ratio, were investigated. For this reason, the epoxy adhesive was used. Joints were prepared with aluminum materials. The stress analyses were employed using the Finite Element Method (FEM). ANSYS (v.14.0.1) FEM tool was utilized to investigate the stress distribution characteristics of aluminum lap joint under tensile loading. Numerical results were found to be quite reasonable. The numerical results show that the influences of variations are very notable when the equivalent stresses are between 18 MPa and 20 MPa. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Öğe The investigation of the tensile behaviors of single L-joint type bonded with adhesive and rivet(Wiley-Blackwell, 2018-08) Adin, Hamit; Kurtkan, Ümitn this study, tensile behaviour of single “L” type joints was investigated experimentally and numerically. Aluminium pieces with 2 mm, 3 mm and 4 mm thicknesses were used as joint materials. Overlap lengths were chosen as 10 mm, 15 mm and 20 mm. Joints were executed with two different rivets as steel and aluminium and 3 M 2216 epoxy based adhesive. Experiments were carried out by means of Shimadzu universal testing machine with 5 kN load cell. While the numerical study was carried out, using ANSYS Workbench, finite element analysis program, models were formed with the same properties as experimental works. Results showed that the samples with 20 mm overlap length had the highest strength of all models. Models with steel rivet had higher strength than models with aluminium rivets for all overlap lengths.Öğe Effect of the air flow rate of blower on the performance of solar still(Türk Isı Bilimi ve Tekniği Derneği, 2015-06-01) Argunhan, Zeki; El, Emin; Yücel, Halit Lutfi; Çakmak, Gülşah; Yıldız, CengizSolar distillation is one of the important methods for water purification. This paper examines the performance of solar distillation system at different air flow rate. To increase the performance of distiller, artificial wind was created by fan and suitable wind speed was investigated to increase the amount of water distilled. The experiments were carried out in Elazığ climate conditions. In order to examine the effect of the wind speed on solar distillation system, two stills were manufactured with the size of 1000x1000 mm. One of them was the conventional still which was used as a reference. The other still was used to investigate experimentally the effect of the wind speed. Graphs were drawn for time-dependent changes in the amount of water distilled. It was found that that the productivity of the fan-still distiller was 14.7 % greater than that of a conventional still.Öğe Investigating the effects of cutting parameters on the hole quality in drilling the Ti-6Al-4V alloy(Materiali in Tehnologije, 2014-10) Çelik, Yahya HışmanIn this study, the effects of cutting parameters on the surface roughness, burr height, hole-diameter deviation, cutting temperature and structure of a chip formation were investigated during the drilling of the Ti-6Al-4V alloy. For this purpose, the Ti-6Al-4V alloy was drilled at different cutting parameters, longitudinally in the 10 mm depth with Ø = 10 mm high-speed-steel (HSS) drills, having 90°, 118°, 130° and 140° point angles on the CNC vertical machining centre. Experiments were carried out at the (12.5, 18.75 and 25) m/min cutting speeds and the (0.05, 0.1 and 0.15) mm/r feed rates without using the cutting fluid. As a result, as the feed rate and the drill-point angle were increased, the surface roughness increased as well; however, as the cutting speed increased, the surface roughness decreased. When the feed rate and drill-point angle increased, the burr height decreased. On the other hand, an increase in the cutting speed increased the burr height. In general, an increase in the feed rate and drill-point angle increased the hole diameters, and the hole diameters obtained were close to the nominal size when the cutting speed was increased.Öğe Emissions from a diesel power generator fuelled with biodiesel and fossil diesel fuels(SAGE Journals, 2015-08-01) Altun, ŞehmusThe aim of this work was to compare the emission characteristics of a biodiesel derived from waste cooking sunflower oil and two fossil diesel fuels (ultra-low sulphur diesel and its type of containing gas-to-liquid). The tests were conducted on a direct-injection diesel engine-powered generator set, which is the type of generator applied in institutional facilities, under variable load and constant engine speed conditions. Experimental results showed that diesel containing gas-to-liquid and biodiesel reduced smoke opacity while NOx emissions were slightly higher for both fuels. An increase in fuel consumption was also observed for biodiesel compared with both fossil diesels. Unburned HC emissions were high for biodiesel, but overall level of CO emissions remained very low for all fuels testedÖğe An investigation of the effect of parameters and chip slenderness ratio on drilling process quality of AISI 1050 steel(Hindawi, 2018-05-08) Demir, Zülküf; Yakut, RıfatThe chip slenderness ratio is a vital parameter in theoretical and applicable machining operations. In predrilled drilling operations of AISI 1050 steel alloy, HSS drills were employed, and the effect of the selected parameters on the chip slenderness ratio and also the effect of the chip slenderness ratio on the thrust force, surface roughness, drilled hole delamination, tool wear, and chip morphology were investigated. The major parameters, influential on the chip slenderness ratio, were feed rate and point angle, while spindle speed was too small to be negligible. With increasing the chip slenderness ratio, the thrust force and the tool wear decreased, which resulted in appropriate chip morphology, but there were increases in surface roughness. However, the chip slenderness ratio had no effect on the drilled hole delamination.
