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Başlangıç ​​tarihi: 2020 × Bölüm: Batman Üniversitesi Mühendislik - Mimarlık Fakültesi Makine Mühendisliği Bölümü ×

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    An exergy analysis of a concentric tube heat exchanger using hBN-water nanofluids
    (Inder Science Publishers, 2021) Budak Ziyadanoğulları, Neşe; Perçin, Süleyman
    This 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).
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    Numerical and experimental investigation of solar chimney power plant system performance
    (Taylor & Francis, 2020-03-15) Karakaya, Hakan; Durmuş, Aydın; Avcı, Ali Serkan
    A 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.
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    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, Hakan
    Exploration 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.
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    An experimental investigation of the effect of thermophysical properties on time lag and decrement factor for building elements
    (Gazi University, 2020-06-01) Oktay, Hasan; Yumrutaş, Recep; Argunhan, Zeki
    The time lag (TL) and decrement factor (DF) are essential for the heat storage capabilities of building elements, which strictly depend on the thermophysical properties of the elements. Many investigations are presented in literature arguing to find the influence of each thermophysical property on TL and DF by keeping the other properties constant. This study aims to investigate the effect of each property on TL and DF, utilizing relationships between the measurement values of the thermophysical properties of wall materials. Therefore, first, 132 new concrete wall samples were produced, and their thermophysical properties were tested. Secondly, TL and DF values for each building element are computed from the solution of the problem by Complex Finite Fourier Transform (CFFT) technique. Finally, a multivariate regression analysis has been performed, and the variations of each thermophysical property versus TL and DF are presented, and also the findings are compared with literature. The results show that each property alone (keeping the other properties constant) is not adequate to identify the thermal inertia and thermal performance of a wall element. Besides, 87.3 % decrease in thermal diffusivity corresponds to 6.03 h increase in the value of TL and 88.8 % decrease in value of DF; respectively, for W1 wall assembly.
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    Farklı kesme parametreleri ve MQL debilerinde elde edilen deneysel değerlerin S/N oranları ve YSA ile analizi
    (Gazi Üniversitesi, 2021-09-21) Gürbüz, Hüseyin; Gönülaçar, Yunus Emre
    Bu çalışmada, AISI 4140 çeliğinin tornalanması işleminde kesme hızı, ilerleme oranı ve MQL debisinin esas kesme kuvvetleri (Fc) ve ortalama yüzey pürüzlülüğüne (Ra) etkisi hem deneysel hem de istatiksel olarak incelenmiştir. Bu doğrultuda deney sonuçlarının değerlendirilmesinde sinyal/gürültü (S/N) oranları ve yapay sinir ağları (YSA) kullanılmıştır. İşleme deneylerinde, kesme parametreleri olarak üç farklı kesme hızı (75, 100, 125 m/dk), üç farklı ilerleme oranı (0,16 - 0,25 – 0,5 mm/dev), üç farklı MQL debisi (0,35 - 0,8 - 1,7 ml/dk) ve sabit kesme derinliği (2,5 mm) seçilmiştir. İşleme deneylerinde MQL debi artışının Fc üzerinde Ra’ya göre daha etkili olduğu tespit edilmiştir. Ayrıca tüm MQL debi uygulamalarında hem Fc hem de Ra’nın ilerleme oranı ile arttığı ve kesme hızı ile genel olarak azaldığı görülmüştür. Fc ve Ra için S/N oranları ve YSA ile elde edilen R2 değerleri R2 S/N(Fc)= 0,9996, R2 S/N(Ra)= 0,9984, R2 YSA(Fc)=0,9990 ve R2 YSA(Ra)=0,9884 bulunmuştur. S/N oranlarına göre Fc ve Ra üzerindeki en etkili kontrol faktörlerinin sırasıyla; ilerleme oranı, kesme hızı ve MQL debi olduğu belirlenmiştir. Elde edilen regresyon değerlerine bağlı olarak S/N oranlarının ve YSA’nın deneysel verileri yüksek güven aralığında tahmin etmede geçerli olduğu tespit edilmiştir
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    Milling Inconel 718 workpiece with cryogenically treated and untreated cutting tools
    (SpringerLink, 2021-07-17) Gürbüz, Hüseyin; Baday, Şehmus
    Although Inconel 718 is an important material for modern aircraft and aerospace, it is a kind material, which is known to have low machinability. Especially, while these types of materials are machined, high cutting temperatures, BUE on cutting tool, high cutting forces, and work hardening occur. Therefore, in recent years, instead of producing new cutting tools that can withstand these difficult conditions, cryogenic process, which is a heat treatment method to increase the wear resistance and hardness of the cutting tool, has been applied. In this experimental study, feed force, surface roughness, vibration, cutting tool wear, hardness, and abrasive wear values that occurred as a result of milling of Inconel 718 material by means of cryogenically treated and untreated cutting tools were investigated. Three different cutting speeds (35-45-55 m/min) and three different feed rates (0.02- 0.03-0.04 mm/tooth) at constant depth of cut (0.2 mm) were used as cutting parameters in the experiments. As a result of the experiments, lower feed forces, surface roughness, vibration, and cutting tool wear were obtained with cryogenically treated cutting tools. As the feed rate and cutting speed were increased, it was seen that surface roughness, vibration, and feed force values increased. At the end of the experiments, it was established that there was a significant relation between vibration and surface roughness. However, there appeared an inverse proportion between abrasive wear and hardness values. While BUE did not occur during cryogenically treated cutting tools, it was observed that BUE occurred in cutting tools which were not cryogenically treated. Also, in this study, the statistical validity of the experimental values was tested with the help of secondorder equations and analyses of variance (ANOVA). R2 values obtained as 99.14%, 99.76%, and 97.98% for vibration, surface roughness, and feed force values were modeled statistically with the help of second-order equations, respectively.
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    The varieties and characteristics of grapes grown in Southeast Anatolia Region
    (Batman Üniversitesi, 2020-12-31) Levent, Abdulkadir; Demir, Zülküf
    Grape is a fruit, called Vitis. Turkey replaces in the first sixth in growing grape, in the world. Grape has a significant place in the food industry. The antioxidants in grape seed have the effect of preventing and treating many diseases. In Turkey, the percentages of grapes, consumed in the form of wort, is about 30 %, annually. The 25 % of grape garbage is seeds. Approximately 3-6 % of grapes seeds (44000 tons) wasted annually. The foreseeing designing and manufacturing the grape squeezing machine will facilitate the work of the grape grower and will achieve the grape seeds to the economy. While the sieve diameter of grape seeds separator, separated the seeds from the garbage of the grape will be less than or equal to 2 mm (≤2 mm), the garbage from the wort is greater than or equal to 8.5 mm (≥8.5 mm), according to the seeds geometrical dimensions, gained.
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    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, Edip
    In 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.
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    Computer aided numerical damage analysis of the axle shaft
    (Ahmet ÇALIK, 2022-09-20) Adin, Hamit; Ergün, Raşit Koray; Adin, Mehmet Şükrü
    Today, while transportation is constantly moving forward, costs are increasing. The aim is to obtain light structures that are suitable in terms of weight, sufficient in strength, and to save materials and energy. Axles are not only used in transport vehicles, but also in buses, automobiles and forklifts. Axles must be of a reliable structure due to their place of use. The external effects that the axles are generally exposed to are the applied loads. In this study, the mechanical damage analysis of the axle shaft and the characteristic changes in steel materials as a result of static loading were investigated numerically. In order to observe the mechanical behavior of the axle shaft under various loading conditions, mechanical tests should be supported by numerical analysis. Because the physical causes of damage development can be understood through numerical analysis. The aim of our study is to reach the most suitable values in the design of the variables with the optimization technique of the axle shaft made of AISI 1035 steel. Optimum values were obtained by performing numerical analyzes of the axle shaft designed with Solidworks program. As a result of the analysis, it was observed that deformation occurred at the ends of the axle.