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Öğe Numerical and experimental investigation of solar chimney power plant system performance(Taylor & Francis, 2020-03-15) Karakaya, Hakan; Durmuş, Aydın; Avcı, Ali SerkanA prototype of a solar chimney power plant was performed by modeling in this study. The performed prototype was experimentally confirmed. Temperature, velocity, and radiation values were measured to actualize the confirmation. Experimental data that were obtained to determine the performance of solar chimney whose prototype was actualized by the help of measured values were computationally analyzed. The geometry of a solar chimney in the analysis was bidimensionally (2D) drawn on an axis of symmetry. The numerical simulation was analyzed with computational fluid dynamics (CFD) method. Since analysis results show that there is turbulent flow in system (RNG), k-ɛ turbulence model was used. Continuity, momentum, and energy equations were applied to the solar chimney system via the finite volume method. Moreover, DO (discrete ordinates) model was inserted in analysis to evaluate the radiation effect in the collector area. In addition to all these, correlation results between SPSS 17 statistics program and data obtained were evaluated. Finally, with reference to the comparison between numerical and experimental results, data obtained and numerical data are close to each other; the prototype is applicable to the real systems.Öğe Investigation of low velocity impact behaviors of honeycomb sandwich composites(SpringerLink, 2018-08-09) Topkaya, Tolga; Solmaz, Murat YavuzHoneycomb sandwich composites are used as significant structural members in advanced engineering applications. Thus, it is critical to determine how they behave under impact loading, in addition to other loads. In this study, low velocity impact loading behaviors of honeycomb sandwich composites were experimentally investigated. Almost all of the design parameters of honeycomb sandwich composites were investigated. The results indicated that the core thickness of honeycomb had no effect on the strength of the composite, and the parameter influencing the impact behavior of the specimen the most was the face sheet thickness. When the face sheet thickness of the specimen was increased, the most apparent strength increase was observed in the models using carbon fiber-reinforced composite face sheets. For all face sheet types subject to impact energy of 10 Joules, the upper face sheets of 0.5 mm-thick specimens were perforatedÖğe Effects of ethanol addition to biodiesel fuels derived from cottonseed oil and its cooking waste as fuel in a generator diesel engine(Taylor & Francis, 2020-03) Karakaya, HakanExploration of energy sources such as renewable and non-edible vegetable oils has been continued during the recent two decades of 2000s. Cottonseed oil is a non-edible, abundant oil and is generally used as cooking oil. In the present study, the usability of biodiesel derived from both cottonseed oil and its cooking wastes was investigated by blending them with ULSD or ethanol in 50 percentages. B50, WB50, B50E50 and WB50E50, biodiesel and ethanol-contained fuels and ULSD were prepared for experiments. Combustion, performance, and emissions tests were conducted on a diesel engine used for power-producing electrical generator. In the combustion tests, cylinder pressure, HRR, CHR, MGT, and MFB were analyzed while MFC, BSFC, exhaust manifold temperature, and thermal efficiency were obtained in the performance tests. In the emissions tests, CO, HC, and NOx emissions were measured and compared with the results of ULSD. Combustion and performance findings of ULSD contained biodiesel blends were found more similar to those of ULSD. The duration of combustion stage can clearly be seen to be narrowed for ethanol-contained blend because of the rabid combustion characteristics of ethanol. Besides, the peak of HRR was found 10% higher for B50E50 while it was found averagely 8% for WB50E50 blends. NOx emissions were found 48% lower averagely for ethanol contained biodiesel blends that it is the most important finding of ethanol using with biodiesel. Besides, HC emissions were also found about 75% for biodiesel contained diesel fuel blends.Öğe Progressive failure analysis in adhesively, riveted, and hybrid bonded double-lap joints(Taylor & Francis, 2013-11) Topkaya, Tolga; Solmaz, Murat YavuzOne of the important processes in structural design is the joining technique. Failure of composite joints involves different failure mechanisms depending upon the joining technique. In this study, a progressive failure analysis was performed on adhesively, riveted, and hybrid bonded double-lap joints. In the joints, a woven-type fiberglass-reinforced composite material was used as the main material; AV 2015 was used as the adhesive, and steel as the rivet material. The analyses were performed using ANSYS 12.1 finite element package software via software written using parametric design language (APDL) codes. At the end of the progressive failure analysis, failure loads and failure modes were determined for 30-, 45-, and 60-mm overlap lengths in accordance with the Maximum Shear Stress Theory and Hashin Criteria. For 45-mm overlap lengths, the joint strength of hybrid joints proved to be 2.72 and 1.145 times higher, respectively, than adhesive and fastening joints. Results showed that the failure load of the joint increased when the overlap length increased. In riveted joints, the failure occurring in the composite plates began around the rivet hole and the catastrophic failure of these types of joints resulted from fiber tensile failure.Öğe Effect of welding parameters on microstructure and mechanical properties of AA7075/AA5182 alloys joined by TIG and MIG welding methods(SpringerLink, 2020) Çelik, Yahya Hışman; Temiz, Şemsettin; Çetkin, EdipIn this study, V and X welding grooves were opened to the forehead positions of the AA5182 and AA7075 aluminum alloy pairs and these alloy pairs were joined with tungsten inert gas (TIG) and metal inert gas (MIG) methods. Three diferent welding currents were used in joints. Gas fow rates of 12 and 17 l/min at the TIG welding and wire feed rates of 38 and 45 cm/min at MIG welding were selected. The efect of the welding grooves, welding current, gas fow rate and wire feed rate on microstructure and mechanical properties were investigated. Microstructures of welding zones were analyzed by an optical microscope and a scanning electron microscope (SEM). Vickers hardness of these zones was also measured. In addition, tensile and fatigue tests were carried out. Fracture mechanisms of failed specimens were conducted after the tensile tests were examined by using SEM. The highest hardness, tensile and fatigue strengths were obtained from the alloy pairs joined by opening X welding groove with TIG welding method. These values were 89 HV, 262.87 MPa, and 131.5 MPa, respectively. Similarly, the lowest tensile and fatigue strengths were obtained from the alloy pairs joined by opening V welding groove in the TIG welding method. These values were, respectively, 94.48 MPa and 19.1 MPa. However, the minimum hardness value was measured as 58 HV from the alloy pairs joined by opening V welding groove with MIG welding methods. In addition, it was observed on the fracture surfaces that the grain distributions and mechanisms difered depending on the welding methods, welding groove, and welding parameters.Öğe Optimum insulation thickness assessment of different insulation materials for mid-latitude steppe and desert climate (BSH) region of India(Journals & Books, 2021-01) Kallioğlu, Mehmet Ali; Sharma, Ashutosh; Chinnasamy, Veerakumar; Chauhan, Ranchan; Singh, TejOne of the most effective techniques that is used for energy wastage in buildings is heat insulation. It is possible due to this application to minimize the fuel quantity and accordingly tolerate toxic emissions by finding the optimum point that gives the maximum efficiency. This study was conducted for Jaipur province in Indian climate geography. Climatic characteristics of the region are Mid-Latitude Steppe and Desert Climate (Bsh). Energy need and heat losses in exterior wall were determined by accepting cooling degree day value as T > 24 °C. Optimum insulation thickness, payback period, annual return and annual return rate for XPS and EPS of two different insulating materials respectively are 0.0383–0.0731, 2.35–1.79, 10.95–12.92, 46.84–37.25.Öğe Archaeozoological study of a unique Late Neolithic pitfrom Tepecik-Çiftlik, central Turkey(Anthropozoologica, 2019-08-16) Gündem, Can YumniThe absence of written evidence from prehistoric periods makes it difficult to understand the origins of sacrifice or offering ceremonies. Archaeological finds from prehistoric periods are the only solid evidence for these acts and rituals. One probable case of animal sacrifice or offering in the Neolithic period has been found at the site of Tepecik-Çiftlik Höyük in central Turkey. This study is focused on a single unique pit, which contained only animal bones and was found in an open space. The contents clearly indicate that this pit can not be interpreted simply as mixed kitchen garbage since an almost complete cattle skeleton as well as sixteen left front leg remains from sheep were placed in the pit after a social, or more specifically, ritual act. Similar pit with similar content was found neither in the close region to Tepecik-Çiftlik nor within Anatolia. The main aim of this study is to introduce a special archaeological find group, those were left after certain prehistoric activity.Öğe Effect of MQL flow rate on machinability of AISI 4140 steel(Taylor & Francis, 2020-06-27) Gürbüz, Hüseyin; Gönülaçar, Yunus Emre; Baday, ŞehmusMany studies were performed about the influence of minimum quantity lubrication (MQL) technique on cutting performance in the literature, but there is no paper examining the effect of different MQL flow rates and cutting parameters on machinability of AISI 4140 material as a whole. In this study, the effects of different MQL flow rates and cutting parameters on surface roughness, main cutting force and cutting tool flank wear (VB), with great importance among the machinability criteria, and forming as a result of the machining of AISI 4140, were revealed. At the end of the experiments, it was determined that rise of flow rate affected main cutting forces positively to a certain extent; yet, it exhibited no significant effect on surface roughness, but reduced VB. Also, it was observed that both main cutting force and surface roughness increased with the increase of feed, while generally decreased with the increase of cutting speed. It was seen that flank wear was positively affected by the increase in flow rate; and this decreased with the increase in flow rate. R2 values obtained as 99.8% and 99.9% for main cutting forces and surface roughness values modeled statistically with the help of quadratic equations, respectively.Öğe A review of phase change materials (PCMs) for thermal storage in solar air heating systems(Journals & Books, 2021-01) Kallioğlu, Mehmet Ali; Sharma, Ashutosh; Chauhan, Ranchan; Chinnasamy, Veerakumar; Singh, TejThe surging energy requirements and greenhouse gas (GHG) emission have directed the research towards the utilization of renewable energy sources especially solar energy. Most of the energy part in domestic and commercial consumption is utilized for air heating and drying which can be improved significantly by utilizing solar air heating applications. The main drawback associated with the solar air heating system (SAHS) is the fluctuation in the availability of solar radiations which can be mitigated by a greater extent with the help of thermal storage. Phase change materials (PCMs) are generally utilized for latent heat storage. The present study reviews the various PCMs utilized in thermal storage with SAHS. Numerous types of PCM materials, their properties and applications in solar air heating system have been reviewed. Heat transfer characteristics enhancement techniques like encapsulation, extended surfaces and conductive particle dispersion have also been studied. The air conditioning demands in the future could be significantly mitigated by utilizing these materials.Öğe Effects of specimen dimensions and impact energy on energy absorption and damage of glass/epoxy composite plates(De Gruyter, 2019-02-21) Deniz, Mehmet Emin; Karakuzu, Ramazan; Algan, BerkIn this study, the impact response of laminated composite plates of various specimen dimensions under various impact energies has been investigated, experimentally and numerically. Glass/epoxy composites with [02/902/02/902]s orientations were manufactured by the hand lay-up technique. Low velocity impact tests were conducted using a CEAST-Fractovis Plus impact test machine for specimens with net impact areas; SQR76 (square with 76 mm edge), SQR150 (square with 150 mm edge) and CIR76 (circle with diameter of 76 mm). Numerical analysis was also carried out via 3DIMPACT transient finite element code including matrix cracking and impact-induced delamination criteria. Absorbed energy and the damage size of specimens were investigated for various impact energies. Delamination areas obtained by finite element were in good agreement with those experimentally obtained up to 50 J of impact energy.
