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Öğe Use of natural deep eutectic solvents for rapid and sensitive extraction of abscisic acid in different food samples prior to spectrophotometric analysis(Eylül 2024)This study aimed to develop a cheap and simple sample preparation method with high application potential for the safe determination of abscisic acid at trace levels in different food samples. In this context, a new sample preparation method based on ultrasound-assisted natural deep eutectic solvent-based liquid-liquid microextraction (UA-NADES-LLME) was developed before the spectrophotometric determination of abscisic acid. Four NADESs were prepared and tested to achieve selective and rapid extraction of abscisic acid from food samples. Important experimental variables affecting the UA-NADES-LLME method were optimized with a univariate strategy. The UA-NADES-LLME method has a working range of 15–800 μg L 1 and a detection limit of 4.5 μg L 1 for abscisic acid. The UA-NADES-LLME method provided a preconcentration factor of 250 and an enrichment factor of 146 for a sample volume of 125 mL. The precision of the UA-NADES-LLME method was investigated by intraday and interday studies for 30, 300 and 700 μg L 1 concentrations of abscisic acid. As a result of the studies, the relative standard deviation of the method varied from 1.7 % to 2.8 %. The accuracy of the UANADES- LLME method was tested with recovery values obtained from standard abscisic acid concentrations added to food samples. Finally, the UA-NADES-LLME method was applied to the prepared food samples with the reference method.The results obtained showed that the UA-NADES-LLME method could be successfully applied to the extraction and determination of abscisic acid in complex matrices.Öğe Investigation of use of hydrophilic/hydrophobic NADESs for selective extraction of As(III) and Sb(III) ions in vegetable samples: Air assisted liquid phase microextraction and chemometric optimization(Mayıs 2024)In this paper, a green, cost-effective sample preparation method based on air assisted liquid phase microextraction (AA-LPME) was developed for the simultaneous extraction of As(III) and Sb(III) ions from vegetable samples using hydrophilic/hydrophobic natural deep eutectic solvents (NADESs). Central composite design was used for the optimization of extraction factors including NADES volume, extraction cycle, pH, and curcumin concentration. Limits of detection for As(III) and Sb(III) were 1.5 ng L 1 and 0.06 ng L 1, respectively. Working ranges for As(III) and Sb(III) were 0.2–300 ng L 1 (coefficient of determination (R2 = 0.9978) and 5–400 ng L 1 (R2 = 0.9996), respectively. Relative standard deviations for As(III) and Sb(III) were 2.2–2.8% and 2.9–3.2%, respectively. Enrichment factor of the method was 184 for As(III) and 172 for Sb(III). The accuracy and precision of the AA-NADES-LPME method were investigated by intraday/interday studies and standard reference material analysis, respectively. Finally, the AA-NADES-LPME method was successfully applied to microwave digested vegetable samples using the standard addition approach and acceptable recoveries were achieved.Öğe Evaluation of antioxidant, antimicrobial, enzyme inhibition activity, and cell viability capacity of Hypericum heterophyllum vent., an endemic species in Turkey’s Flora(Mart 2024)The aim of this study was determined the antioxidant, antimicrobial, enzyme inhibition activity, and cell viability capacity of H. heterophyllum (endemic species in the Flora of Turkey) extracts. H. heterophyllum methanolic extract was used in this study. H. heterophyllum plants collected at the beginning of flowering and during full flowering. P content was determined with calorimetrically in spectrophotometer. K, CA, Mg, Fe, Mn, Zn and Cu was determined with Atomic Absorption and N concentration were determined according to the Kjeldahl distillation method. H. heterophyllum (endemic species in the Flora of Turkey) extract was evaluated for its antioxidant (DPPH, ABTS, total phenol and flavonoid content), antimicrobial (four bacteria (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus) and two Candida species (Candida albicans and Candida tropicalis)), enzyme inhibition activity (ɑ-glucosidase, ɑ-amylase, acetylcholinesterase, butyrylcholinesterase, tyrosinase), and cell viability (XTT assay) capacity. Extracts from the beginning of flowering period showed stronger biological activity. It has been determined that the extracts have antioxidant, antibacterial (against Staphylococcus aureus) anticancer activity (on breast cancer cells), and inhibition effects of BChE and alphaglucosidase. It has been determined that the extracts obtained from H. heterophylum have important pharmacological activities, and the plant exhibits higher activity in the BF period. Hypericum heterophyllum Vent. The activities of the chemicals contained in it against various proteins that are α-gly enzyme (PDB ID: 1R47), AChE enzyme (PDB ID: 4M0E), BChE enzyme (PDB ID: 5NN0), alpha-Amylase (PDB ID: 3BAJ), breast cancer protein (PDB ID: 1A52 and 1JNX), were compared. ADME/T analysis of molecules with high activity was performed.Öğe Improved methane production from ultrasonically-pretreated secondary sedimentation tank sludge and new model proposal: Time series (ARIMA)(2024) Görgün EmreSecondary sedimentation tank sludge (SSTS) is a severe type of waste that needs to be treated to prevent human health risks. Anaerobic digestion (AD) alone can be ineffective for treating SSTS due to low substrate biodegradability. This study proposes the use of ultrasonic pretreatment (UP) on SSTS for 0 – 60 min. UP effect on SSTS was analyzed through the actual specific energy input, nominal energy input, and soluble chemical oxygen demand. The highest cumulative methane yield (CMY) of 241.56 mL/g VS obtained during the AD of the pretreated substrate (i.e., 30 min) was 58.4% higher than that of untreated SSTS. The resulting CMY curves were subsequently simulated via the modified Logistic and Gompertz, Artificial Neural Network, Auto-Regressive Integrated Moving-Average (ARIMA) models. As a novel proposal for predicting CMYs, the ARIMA model is recommended due to its simplicity and better performance than sigmoidal models (R2 = 0.9975 – 0.9988).Öğe Ultrasonic testing and surface conditioning techniques for enhanced thermoplastic adhesive bonds(2024) Görgün EmreThis study focuses on the optimization of the bonding conditions for adhesive joints, specifically targeting PA66/GF and epoxy/CF thermoset materials. The Box-Behnken (BB) design was employed for meticulous optimization, considering variables such as mixing ratio (M1), curing time (M2), and primer application (M3). The quadratic model derived from BB demonstrated synergistic effects between variables, allowing for an accurate prediction of response strength. Ultrasonic testing has emerged as a powerful nondestructive evaluation (NDE) tool for assessing bond quality in thermoset materials. PA66/GF and epoxy/CF specimens underwent thorough examination, emphasizing the advantages of non-destructive techniques over traditional destructive tests. The results of the destructive lap shear tests provide a comprehensive understanding of the bonding conditions. The control specimen exhibited a load of 23.7 MPa, while the S-5 group of specimens with modified bonding conditions exhibited higher maximum loads (24.9 MPa), and the S-25 group exhibited a higher maximum loads of 25.6 MPa. The results obtained in this study effectively separated the samples with different adhesion conditions from the control sample. The developed model for the variation of bonding conditions exhibited high prediction accuracy, supported by significant F-values from the ANOVA tests. The regression coefficient (R-square value) of 0.9557 underlines the strong correlation between the variables, with M3 and M2 identified as the key factors. Correlating ultrasonic signals with shear load reveals a strong predictive relationship, with ratios of 0.94 (PA66/GF-adhesive interface) and 0.96 (Epoxy/CF-adhesive interfaces). The model effectively discerns the need for epoxy/CF adhesive interfaces, highlighting potential challenges for the BB-based approach. As the study concludes, the abstract encapsulates the optimization, evaluation, and predictive capabilities of the proposed model for adhesive bonding conditionsÖğe Coupled cylindrical quantum well wires in broken symmetry: effects of intense laser field on the harmonic generations(Springer Nature, 21.10.2024) Alaydin Behçet Özgür; Ozan Öztürk; Didem Altun; Emine ÖztürkThis study explores the high harmonic generations in GaAs/AlxGa1-xAs asymmetric coupled cylindrical quantum well wires (CCQWWs) under varying intense laser fields (ILFs). The structural parameters and theoretical framework are detailed, including the Schrödinger equation for the CCQWW heterojunction and the Floquet method to model ILF effects. Numerical simulations reveal alterations in the confinement potential and energy states of CCQWWs with increasing ILF intensity. Notably, significant changes occur in the potential well shape, influencing the localization of energy states. Transition energies and dipole moment matrix elements are analyzed, highlighting shifts in resonance peaks and their intensities. The study identifies blue-shift points at α0 (ILF parameter) values of 4.4 nm, 4.7 nm, and 3.7 nm for transition energies E21, E31/2, and E41/3, respectively, followed by red-shift trends as α0 increases further. Maximum enhancements are observed in the second harmonic generation coefficient at ILF α0 = 6 nm and the third harmonic generation coefficient at α0 = 8 nm, which is 1000 times higher than at α0 = 0 nm. These findings underscore the potential for enhancing semiconductor device production through optimized ILF induced high harmonic generation.Öğe CH4 production potential of autotrophic nitrification bacteriaproduced in the submerged nitrification bioreactor in thelaboratory and kinetic analysis(07.07.2024) Alhraishawi, AliIn this study, CH4 production capacity of nitrification bacteria (NB) obtainedfrom the submerged biofilter in the laboratory was investigated. Biochemicalmethane potential (BMP) test was carried out with the NB amount of zero(control, CR), 5% (R1), 10% (R2), and 15% (R3) at a temperature of about 37 ±0.5°C. Compared to the CR, significantly higher cumulative CH4 volume ofabout 290, 490, and 715 mL were determined in the R1, R2, and R3, respec-tively. All the applied kinetic models gave good results (R2 ≥0.97), while theTransference Function and First-order models provided the better R2 values.The delay phase (λ) was not observed in the AD process, and CH4 productionstarted immediately on the first day of operation. The predicted k value of0.133 day−1 was high in CR, while it was approximately between 0.078 and0.112 day−1 for the higher amount of NB containing BMP units, which indi-cated that the AD required long reaction time.Öğe Effects of microwave irradiation at various temperatures onbiosludge disintegration(18/06/2024) Alhraishawi, AliThe waste biological sludge disintegration by using microwave irradiationwas investigated at a ramping rate of 2°C/min and 5 min holding time atvarious target temperatures. Significant disintegration of biosludge wasobserved and the highest disintegration degree was determined about82% at the temperature of 110°C. Increase of target temperature elevatedthe energy needs to 98, 123 and 148 kWh/kg TS at the temperatures of75°C, 90°C and 110°C, respectively. The gradual increase of sugar andprotein in the sludge slurry with increasing temperatures indicates suc-cessful degradation. The microwave pretreatment increased the specificsurface area of the sludge by particle size reduction. The specific surfacearea of raw sludge was 70 m2/kg and rose to approximately 253.7 m2/kg at110°C with an increment ratio of 260%. Although a significant NH4–Nrelease was not observed, PO4–P concentrations increased from 11.0 mg/Lto 16.3, 20.7 and 29.2 mg/L at the temperatures of 75°C, 90°C, 110°C,respectively. While the specific filter resistance of waste biological sludgewas about 1.0 × 1013, increasing the microwave target temperature, theability of dewatering decreased and the highest SFR value of 5.1 × 1014was observed at the temperature of 110°C.Öğe Imidazole-Derived Alkyl and Aryl Ethers: Synthesis, Characterization, In Vitro Anticancer and Antioxidant Activities, Carbonic Anhydrase I–II Inhibition Properties, and In Silico Studies(03/05/2024) Faris, Mays; Özcan, İbrahim; Erdoğan, Taner; Tahtacı, HakanImidazole derivatives display extensive applicationsin pharmaceutical chemistry and have been investigated asbioactive compounds for medicinal chemistry. In this study,besides the starting materials (3a−c and 4a−c), synthesis,characterization, and biological activity studies were conductedon a total of 18 compounds, nine of which are known and the othernine are original. The compounds investigated in the study are aseries of alkyl (7−15) and aryl (16−24) ether derivatives bearingsubstituted phenyl and imidazole rings, which were characterizedusing various methods including 1H NMR, 13C NMR, FT-IRanalysis, elemental analysis, and mass spectroscopy. Computer-aided drug design studies have been carried out to predict the biological activities of compounds. Besides DFT calculations, thebinding affinities of the compounds to EGFR, VEGFR2, FGFR1, HSP90, hCA I, and hCA II were investigated. Additionally, drug-likeness and ADME analyses were performed on the compounds. Anticancer, antioxidant, and enzyme inhibition activity tests wereperformed in biological activity studies on the synthesized compounds. Among the synthesized compounds, compounds 17 and 19−24 generally exhibited inhibition profiles against the widespread cytosolic hCA I isozyme with IC50 values ranging from 4.13 to 15.67nM and cytosolic hCA II isozyme with IC50 values ranging from 5.65 to 14.84 nM. L929 (mouse fibroblast cell line) was used as thecontrol healthy cell line, and MCF7 (breast cancer), C6 (rat glioblastoma), and HT-29 (colon cancer) cells were used in cell culturestudies as cancer cell lines. Before the study on cancer cells, all compounds were examined on healthy cells, and their cytotoxicity wasdetermined. As a result of these data, studies continued with six compounds determined to be nontoxic. On cancerous cells, it wasdetermined that compounds 3a, 3b, 4a, 4b, 4c, and 7 had cytotoxic effects on both colon cancer and brain tumors. It was found thatcompound 3b had a more toxic effect than cisplatin on the glioma cell line with an IC50 value of 10.721 ± 0.38 μM, and compound3a had a more toxic effect on the colon cancer cell line with an IC50 value of 20.88 ± 1.02 μM. However, it was determined that thesame compounds did not have a statistically significant effect on breast cancer. Flow cytometry studies also showed that when theIC50 dose of compound 3b was applied to the C6 cell line, the cells tended to early and late apoptosis. Additionally, it has beenshown by flow cytometry that the cell cycle stops in the G0/G1 phase. A similar effect was observed in the colon cancer cell line withcompound 3a. Compound 3b caused early and late apoptosis of the colon cancer cell line with the applied IC50 dose and stopped thecell cycle in the G0/G1 phase. Finally, the FRAP method studied all synthesized compounds’ antioxidant effects. According to themeasured antioxidant power results, it was determined that no compound had a more effective reducing power than vitamin E.Öğe Zaman Gecikmeli Kesir Dereceli Kaotik Sistemlerin Senkronizasyonu ve FPGA Uygulaması(Black Sea Journal of Engineering and Science, 15.07.2024) Değirmen, Semih CanElektronik tabanlı sistemlerin kontrolü, geliştirilmesi ve birçok işletme hatasının tespiti için matematiksel olarak ifade edilebilmesi oldukça önemlidir. Matematiksel olarak ifade edilebilen sistemlerde, geliştirilebilmesinin yanında birçok problemin tespit edilmesini de kolaylaştırır. Özellikle haberleşme sistemleri ve bu sistemlerdeki taşıyıcı sinyallerin, haberleşme protokollerinin matematiksel modellenmeleri ve geliştirilmesi ile ilgili çalışmalar son dönemde artmaktadır. Özellikle karmaşık yapısı ile dikkat çeken kaotik tabanlı sistemlerin haberleşme sistemlerinde kullanılmasıyla bilgi sinyallerinin güvenilirliği artırılmıştır. Ancak kaotik sistemlerin tam dereceli olarak modellenmesi, özellikle kullanıldığı haberleşme sistemlerindeki hatalı bit sayılarını artırmakta ve zaman gecikmelerinden kaynaklı uzun senkronizasyon sürelerine neden olmaktadır. Bu nedenle kaotik sistemlerin kesir dereceli olarak modellenmesinin yanında verici-alıcı sitemlerin mümkün olan en kısa sürelerde senkronize olmaları için sistemler arasındaki zaman gecikmelerinin de dikkate alınması gereklidir. Bu çalışmada haberleşme sistemlerinde kullanılan kaotik bir sistemin kesir dereceli olarak elde edilmesi, daha sonra ise bir kontrolör ile zaman gecikmelerinden kaynaklı senkronizasyon gecikmelerinin azaltılması amaçlanmıştır. Yapılan çalışmada Charef yaklaşım metodu kullanılarak kesir dereceli kaotik sistem tasarımı yapılmış ve bulanık mantık tabanlı bir kontrolör ile zaman gecikme sürelerinden kaynaklı senkronizasyon süresi azaltılmıştır. Neticede, kesir dereceli olarak gerçek sistem davranışı elde edilen bir kaotik sitemin bir kontrolör ile senkronizasyon sürelerinin azaltılabildiği gösterilmektedir. Yapılan çalışma önce bilgisayar benzetimi ile daha sonra ise FPGA kullanılarak deneysel uygulaması gerçekleştirilmiş ve doğrulanmıştır.Öğe LSTM Deep Learning Techniques for Wind Power Generation Forecasting(Journal of Soft Computing and Artificial Intelligence, 15.06.2024) Ahmed Babiker Abdalla, IbrahimWind power generation forecasting is crucial for the optimal integration of renewable energy sources into power systems. Traditional forecasting methods often struggle to accurately predict wind energy production due to the complex and nonlinear relationships between wind speed, weather parameters, and power output. In recent years, deep learning techniques have emerged as promising alternatives for wind power forecasting. This conference paper provides a comprehensive review of deep learning techniques, with a specific focus on Long Short-Term Memory (LSTM) networks, for short-term wind power generation forecasting. Leveraging insights from recent research and empirical evaluations, this paper explores the effectiveness of LSTM networks in capturing temporal dependencies in wind data and improving prediction accuracy. The review highlights the potential of LSTM-based models to enhance the integration of wind energy into power systems and provides guidance for future research in this area.Öğe A beetroot-based beverage produced by adding Lacticaseibacillus paracasei: an optimization study(2024) Durukan Gamze; Sari FerdaThe present study aimed to optimize the production conditions of a beetroot-based beverage using Lacticaseibacillus paracasei. The experiment was meticulously planned and executed using the Box–Behnken design in Response Surface Methodology (RSM), which provided 17 different combinations. The independent variables in this study included the heat treatment temperature (60–80℃, the heat treatment time (10–30 s), and the incubation temperature (24–36℃). The variables evaluated in this study included pH, total acidity (TA), total phenolic content (TPC), total betalain content (TBC), yellow color (OD420), general acceptance (GA), and total count of lactic acid bacteria (LAB). The samples were determined to have TPC ranging from 67.90 to 437.15 mg GA/L and TBC ranging from 147.52 to 747.21 mg/L. The samples subjected to incubation temperatures of 30℃ and 36℃ were typically favored by the panelists and exhibited better results in terms of chemical analysis compared to the samples incubated at 24℃. According to RSM, heat treatment at 60°C for 22 min and an incubation temperature of 31°C were the optimum production conditions. Under these optimal conditions, RBJ has maximum TBC, total LAB, and GA scores, indicating nutrient-dense and appealing to consumers.Öğe Linear and nonlinear optical properties of a superlattice with periodically increased well width under electric and magnetic fields(Micro and Nanostructures, Nisan 2022) Altun, Didem; Öztürk, Ozan; Alaydin, Behçet Özgür; Öztürk, EmineIn this paper, we have studied the electronic and optical properties of GaAs/AlxGa1-xAs superlattice with periodically increased well width. Under effective mass approximation, the finite element method is used to obtain wavefunctions and corresponding energy eigenvalues for several electric field (F) and magnetic field (B) values. We have shown that the increasing well width has a major effect on the localization of the first two energy states. The direction of the applied electric field shifts the localization position of the probability density of electrons to the left and right. For B = 0 (according to the parameters used), F = 5 kV/cm (especially for the difference between the first two energy levels (E12)) is a critical value. While the E12 value decreases in the range from 30 kV/cm to 5 kV/cm, it increases for the 5 < F < 30 kV/cm range. This behavior causes a red or blue shift in the optical spectrum. Also, F = 30 kV/cm causes more change in the structure than F = 30 kV/cm. In addition, the localization of the electrons is observed in the center of the superlattice under applied magnetic fields. The optical absorption coefficients and the refractive index changes are affected by applied F and B intensities. We can say that the electro-optical features of the superlattice have changed significantly with the combined effect of F and B values. This is desired for semiconductor optical device applications to have stable performances.Öğe Linear and nonlinear optical properties of a superlattice with periodically increased well width under electric and magnetic fields(Micro and Nanostructures, Nisan 2022) Altun, Didem; Öztürk, Ozan; Alaydin, Behçet Özgür; Öztürk, EmineIn this paper, we have studied the electronic and optical properties of GaAs/AlxGa1-xAs superlattice with periodically increased well width. Under effective mass approximation, the finite element method is used to obtain wavefunctions and corresponding energy eigenvalues for several electric field (F) and magnetic field (B) values. We have shown that the increasing well width has a major effect on the localization of the first two energy states. The direction of the applied electric field shifts the localization position of the probability density of electrons to the left and right. For B = 0 (according to the parameters used), F = 5 kV/cm (especially for the difference between the first two energy levels (E12)) is a critical value. While the E12 value decreases in the range from 30 kV/cm to 5 kV/cm, it increases for the 5 < F < 30 kV/cm range. This behavior causes a red or blue shift in the optical spectrum. Also, F = 30 kV/cm causes more change in the structure than F = 30 kV/cm. In addition, the localization of the electrons is observed in the center of the superlattice under applied magnetic fields. The optical absorption coefficients and the refractive index changes are affected by applied F and B intensities. We can say that the electro-optical features of the superlattice have changed significantly with the combined effect of F and B values. This is desired for semiconductor optical device applications to have stable performances.Öğe Dikey Bir Kanalda Bulunan Farklı Şekilli Elektronik Eleman Çiftinden Olan Taşınım Isı Transferinin Değerlendirilmesi(TMMO, Eylül-Ekim 2024.)Bu çalışmada, birbirine paralel dikey levhaların sol yüzeyi üzerinde iki adet yamuk geometrili sabit ısı akılı elektronik engel bileşenlerinin bulunduğu bir kanalda karışık taşınımla ısı transferi ve engeller etrafındaki akışkan hareketi sayısal olarak incelenmiştir. Sayısal araştırma, zamandan bağımsız, laminer ve iki boyutlu olarak süreklilik, momentum ve enerji denklemlerinin Ansys-Fluent bilgisayar programıyla çözülmesiyle gerçekleştirilmiştir. Akışın kanal içerisindeki ısınmış engel elemanlarına yönlendirilmesi amacıyla kanalın sağ üst yüzeyiyle 30o ve 45o açı yapan akış yönlendirici kanatçıklar yerleştirilmiştir. Kanalın engel elemanları harici diğer yüzeyleri ve akış yönlendiriciler adyabatiktir. Kanalda kullanılan su akışkanı sıkıştırılamaz olup, kanala giriş sıcaklığı 293 K’ dir. Çalışmada kullanılan Reynolds sayısı (Re) değeri 1000 iken; değiştirilmiş Richardson sayısı (Ri*) aralığı 50-150 ve Akış Geçiş Mesafesi (AGM) oranları 3.33 ve 4 olarak alınmıştır. Çalışmanın sonuçları, literatürdeki deneysel ve sayısal sonuçlarla kıyaslanmış ve oldukça uyumlu oldukları görülmüştür. Sonuçlar, Ri* sayısına göre farklı AGM ve kanatçık açılarında engellerin toplam ortalama Nu sayıları (Num), yüzey sıcaklıkları (Ts) ve akışkanın basınç düşüşünün (∆p) değişimleri olarak incelenmiştir. Ayrıca, değişik AGM oranları ve Ri* değerlerinde karışık taşınımın hız ve sıcaklık konturu dağılımları değerlendirilmiştir. AGM’nin 4 ve Ri*=150 olduğu değerler için Num sayısının 45o açılı kanatçıklı durumda kanatçıksız duruma göre %1.54 daha fazla olduğu belirlenmiştir.Öğe Elmas-Su Nanoakışkanı Kullanılan Kanatçıklı ve Farklı Yükseklikli Birleşik Jet Akışlı Kanallarda Yüzeylerin Soğutulması(Gazi Üniversitesi, 29.02.2024) Karabulut, Koray; Alnak, Doğan EnginÇarpan jet-çapraz akıştan oluşan birleşik jet etkisi elektronik elemanların soğutma performansını artırıcı bir etkiye sahiptir. Bu çalışmada, birleşik jet akışıyla kanatçıksız ve 30o açıya sahip kanatçıklı, N=2D kanatçık mesafeli ve H=3D ve 4D yükseklikli kanallarda su ve %2 hacimsel konsantrasyonlu Elmas-Su nanoakışkanı kullanılmasıyla küp ve yamuk modelli yüzeylerden olan ısı transferi ve performans analizi sayısal olarak incelenmiştir. Sayısal araştırma, sürekli ve üç boyutlu, k-ε türbülans modelli Ansys-Fluent programıyla gerçekleştirilmiştir. Literatürdeki çalışmalar gözetilerek kanal boyutlarına uygun olarak kanallara üçer adet model yerleştirilmiştir. Kanaldaki akışkanların Re sayısı aralığı 5000-9000’ dir. Sonuçlar, literatürdeki deneysel çalışmanın Nu sonuçlarıyla kıyaslanmış ve uyumlu oldukları belirlenmiştir. Çalışmanın sonuçları, kanallardaki her bir model için ortalama Nu sayısı ve yüzey sıcaklığının değişimleri olarak su ve nanoakışkan için kanatçıksız ve kanatçıklı durumlarda farklı kanal yüksekliklerinde karşılaştırmalı olarak incelenmiştir. Ayrıca, birleşik jet nanoakışkan akışının hız ve sıcaklık konturu dağılımları sunulmuştur. Bununla birlikte, kanallardaki her üç model yüzeyinin tümü için farklı Reynolds sayılarında performans değerlendirme sayıları (PEC) ve Re=7000 için ortalama Nu sayısı (Num) ve yüzey sıcaklık değerleri (Tm) değerlendirilmiştir. H=3D ve kanatçıklı kanalda Elmas-Su nanoakışkanının kullanılması kanatçıksız ve su akışkanı kullanılan kanala göre küp ve yamuk modelli yüzeylerde Num değerlerinin sırasıyla %24,14 ve %18,91 daha fazla olmasını sağlamıştır.Öğe Bakır Oksit-Su ve Elmas-Su Nanoakışkanlı Birleşik Jet Akışlı Kanallarda Isı Transferi ve Akış Yapılarının Değerlendirilmesi(Düzce Üniversitesi, 26.01.2024) Karabulut, KorayBu çalışmada, sabit 1000 W/m2 ısı akısına sahip dairesel oyuklu ve yamuk modelli bakır plakalı yüzeylerden olan ısı transferi ve birleşik jet akışlı kanallardaki akış yapıları su, %2 hacimsel konsantrasyonlu CuO-Su (Bakır oksit)-Su ve Elmas-Su nanoakışkanları kullanılarak sayısal olarak incelenmiştir. Sayısal çalışma, sürekli ve üç boyutlu olarak k-ε türbülans modelli Ansys-Fluent programının kullanılmasıyla gerçekleştirilmiştir. Kanallara ayrıca jet girişinden itibaren D jet giriş çapı ölçüsündeki sabit bir uzaklıkta (N) 45o ve 90o açılı kanatçıklar eklenmiştir. Kanal yüksekliği 3D iken; akışkanların Re sayısı aralığı 5000-15000’ dir. Çalışmadan elde edilen sonuçların doğruluğu ve kabul edilebilirliği deneysel araştırmalar sonucu elde edilen eşitlik kullanılarak kanıtlanmıştır. Çalışmanın sonuçları, kanallardaki her bir model için ortalama Nu sayısının değişimleri olarak su ve nanoakışkanlar için kanatçıksız ve kanatçıklı durumlarda karşılaştırmalı olarak değerlendirilmiştir. Ayrıca, CuO-Su nanoakışkanı için birleşik jet akışın hız ve sıcaklık konturu dağılımları farklı kanatçık açıları için sunulmuştur. Bununla birlikte, kanallardaki her üç desenli yüzeyin tümü için farklı Reynolds sayılarında performans değerlendirme sayıları (PEC) ve ortalama Nu sayısı (Num) ve yüzey sıcaklık değerleri (Tm) Re=5000 ve 15000 için analiz edilmiştir. Re=15000 için 90o kanatçıklı kanalda yamuk modelli yüzeyde sırasıyla Elmas-Su ve Bakır oksit-Su nanoakışkanları kullanılması durumları için kanatçıksız ve su akışkanı kullanılan kanallara göre Num sayısında %27,57 ve %26,11’ lik artışlar elde edilmiştir. Bunun yanı sıra, Re=15000 değerinde 90o açılı kanatçıklı kanallarda su akışkanı için PEC sayısı değerlerinin sırasıyla dairesel oyuklu ve yamuk modelli yüzeylerde Elmas-Su ve CuO-Su nanoakışkanlarına göre %1,1-%1,31 ve %0,82-%0,63 daha fazla oldukları tespit edilmiştir.Öğe The effects of rectangular baffle angles and heights on heat transfer and pressure drop performance in cross-triangular grooved rectangular flow ducts(Elsevier, FEB 2024) Karabulut, KorayThe improvements in heat exchangers mainly focus on rising energy efficiency. The cross-grooved rectangular flow ducts are largely used for plate heat exchangers. In this study, to enhance the heat transfer and hydraulic-thermal performance in the cross-grooved rectangular ducts with triangular grooves, rectangular baffles were located in the duct, and the influences of the rectangular baffle angles and heights on the features of the heat transfer and pressure drop were numerically analyzed in detail. The equations of Navier-Stokes and energy were solved by employing the Ansys-Fluent program with the k-ε turbulence model as steady and three-dimensional. Air used as working fluid has an inlet temperature of 293 K while the triangular groove’s wall temperature is 373 K. Rectangular baffles have various angles of 30°, 60°, and 90°, and heights of 0.25H, 0.5H, and 0.75H. The mean Nusselt number (Num), dimensionless temperature (T*), turbulence kinetic energy (TKE*), pressure (p*), and performance evaluation criterion (PEC) number of the ducts with rectangular baffles were evaluated by comparing with the cross-triangular grooved duct without baffle. Also, the contours of turbulence kinetic energy, temperature, and velocity vector were exhibited for the cross-triangular grooved rectangular ducts with different arrangements of baffle angles and heights. Results were matched with experimental and computational outcomes of the study found in the literature, and it was observed that they were fairly compatible. The increment rate of Num at 90° baffle angle and 0.75H height is 197.56 % higher for Re = 6000 compared to 0.25H. Besides, for Re = 1000, the PEC number is 84.50 % higher at 0.25H baffle height and 30° angle than at 90°.Öğe Investigation of Heat Transfer Increment in Electronic System Surfaces by Different Air Jet Impingement Applications(PLEIADES PUBLISHING INCPLEIADES HOUSE, 7 W 54 ST, NEW YORK, NY 10019, UNITED STATES, MAR 2024) Karabulut, Koray; Alnak, Doğan EnginThe impinging jet technique is a high-performance cooling technology for microchips which are basic elements of electronic systems and having high heat generation rates in small volumes. In this study, the improvement of heat transfer of the microchips used in all technological products today by air impinging jet has been examined. For this purpose, numerical research has been carried out on the cooling of copper plate surfaces with two different patterns, reverse triangle and reverse semi-circle shaped having 1000 W/m2 constant heat flux in rectangular cross-section ducts with adiabatic surfaces, by one and double air jets with distances of Dh and 2Dh between them. Numerical computation has been performed for energy and Navier-Stokes equations as steady and three-dimensional by employing the Ansys-Fluent computer program with the k-epsilon turbulence model. The obtained results have been compared with the numerical and experimental results of the study in the literature and it has been seen that they are compatible with each other. The results have been presented as the mean Nu number and the variation of surface temperature for each of both patterned surfaces in single and double jet channels with different distances. Streamline and temperature contour distributions of the jet flow along the channel for different H/Dh ratios and jet numbers have been evaluated for both patterned surfaces. In double-jet and 2Dh distance channels compared to Dh, at H/Dh = 12 and Re = 11,000, the Nu number increases of 67% and 65.9% have been observed on the first-row reverse triangle and semi-circular patterned surfaces, respectively.Öğe Heat transfer and thermal-hydraulic evaluations of cross-circular grooved rectangular flow ducts depending on rectangular baffle design parameters(SPRINGER HEIDELBERGTIERGARTENSTRASSE 17, D-69121 HEIDELBERG, GERMANY, MAR 7 2024) Karabulut, KorayThe cross-grooved rectangular flow ducts are largely used for plate heat exchangers. In this work, so as to better the heat transfer in cross-grooved rectangular ducts with circular grooves, rectangular baffles were located in the flow duct, and the influences of the rectangular baffle angles and heights on the features of heat transfer were numerically performed in detail. Equations of Navier–Stokes and energy were resolved by employing a program of Ansys-Fluent with k–ε turbulence model as steady and three-dimensional. Air employed as working fluid has a temperature of inlet 293 K while the circular groove’s wall temperature is 373 K. Rectangular baffles have various angles of 30°, 60°, and 90°, and heights of 0.25 H, 0.5 H, and 0.75 H. The mean Nusselt number (Num), temperature, turbulence kinetic energy (TKE), pressure, and PEC (Performance Evaluation Criterion) number of the flow duct with rectangular baffles were evaluated by comparing it with the cross-circular grooved channel non-baffle. Besides, the contours of velocity, turbulence kinetic energy, temperature, and velocity vector were exhibited for the cross-circular grooved rectangular channels with different baffle angles and height arrangements. Results were matched with experimental and numerical outcomes of the study found in the literature, and it was observed that they were fairly coherent. For Re 6000, the number of Num increases by 180.48% in the duct with a 90° angle and 0.75 H baffle height compared to the duct non-baffle, and for 30° baffle angle, the PEC value at 0.25 H baffle height is 66.88% higher than that in the 0.5 H.
