Toprak, Kasım
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Toprak, K
Toprak, K.
Toprak, Kasim
Toprak, K.
Toprak, Kasim
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kasimtoprak@iyte.edu.tr
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03.10. Department of Mechanical Engineering
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1NO POVERTY
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2ZERO HUNGER
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3GOOD HEALTH AND WELL-BEING
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4QUALITY EDUCATION
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5GENDER EQUALITY
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6CLEAN WATER AND SANITATION
1
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7AFFORDABLE AND CLEAN ENERGY
2
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8DECENT WORK AND ECONOMIC GROWTH
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
4
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
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9
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68
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3
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12
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6
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6509/3663
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5
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WoS Citation Count
12
Scopus Citation Count
11
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3
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1.00
Scopus Citations per Publication
0.92
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8
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5
| Journal | Count |
|---|---|
| Modelling and Simulation in Materials Science and Engineering | 2 |
| Heat Transfer Research | 1 |
| International Journal of Energy Research | 1 |
| Kocaeli Journal of Science and Engineering | 1 |
| Politeknik Dergisi | 1 |
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12 results
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Now showing 1 - 10 of 12
Article Citation - Scopus: 1Genetic Algorithm Optimization of Langevin Thermostat and Thermal Properties of Graphene-Aluminum Nanocomposites: a Molecular Dynamics(Iop Publishing Ltd, 2024) Toprak, KasimThe thermal properties of a laminated structure of graphene-coated aluminum composite nanomaterial were investigated through non-equilibrium molecular dynamics (NEMD) simulations to address the problem of temperature deviation in the thermostat volume applied. This paper presents a new insight into the best values of timestep and Langevin thermostat damping parameters for each atom in the nanomaterial with different size configurations using the genetic algorithm (GA) method by considering the timestep and thermostat damping parameters for each atom type, as well as the thickness of the nanomaterial, the thermostat, buffer, and heat flow lengths. The initial population results indicate that the thermostat temperature deviation increases with higher thermostat damping coefficients and timestep. However, the deviation decreases significantly with increased heat flow and thermostat lengths. Variations in buffer length and aluminum thickness do not have a significant effect on temperature. The application of a GA for optimization leads to a decrease in thermostat temperature deviation. The optimized parameters resulted in better thermostat temperature deviations when analyzing the temperature, aluminum thickness, and both buffer and thermostat lengths. Additionally, the thermal conductivity of aluminum-graphene nanomaterial decreases with increasing temperature, buffer length, and aluminum thickness, but increases by up to 9.85% with increasing thermostat length.Article Non-Equilibrium Molecular Dynamics for Calculating the Thermal Conductivity of Graphene-Coated Aluminum(2020) Toprak, Kasım; Yılmaz, Ahmet BerkNon-equilibrium Molecular Dynamics (NEMD) simulations have been created in C++ using Message Passing Interface (MPI) library to calculate the phonon thermal conductivity of bare graphene, aluminum, and graphene-coated aluminum. This study focuses on how graphene can alter the thermal conductivity of graphene-coated aluminum. The effect of length, graphene, and the number of graphene layers are analyzed. Even though electrons are dominant on thermal conductivity of aluminum, the effect of graphene coating can be seen in the results. The results show that the thermal conductivity of aluminum increases by up to 149% by graphene coating. When the number of layers increases to two layers, the thermal conductivity increases by up to 261%. Moreover, the results increase with the length of all models.Master Thesis Hidrojen Zenginleştirilmesinin Benzinli Motorlar Üzerindeki Etkilerinin Sayısal Analizi(2025) Arslan, Rasim; Toprak, KasımANSYS Fluent 2024 R1'de dört zamanlı kıvılcım ateşlemeli bir motorun iki boyutlu bir kesitine entegre bir hesaplamalı akışkanlar dinamiği (HAD) ve kimyasal kinetik çerçevesi uygulanarak, 2000 dakikadaki devir sayısında (rpm) 360o –1080o krank açısı (KA) döngüsü boyunca silindir içi yanma ve emisyonlar üzerinde hidrojen zenginleştirmesinin (%0, %5, %10, %20, %30 hacimce) silindir içi yanma ve emisyonlar üzerindeki etkilerini araştırmak için uygulanmıştır. Yakıt olarak tanımlanan 54 tür ve 269 reaksiyondan oluşan bir CHEMKIN mekanizması benzin yerine ikame yakıt olarak n-heptan karakterize edilmiştir. Türbülans (k-ε ve k-ω) ve radyasyon modelleri (P1 ve Rosseland) karşılaştırılmıştır. Elde edilen sonuçlar, hidrojen içeriğindeki artışın, silindir içi sıcaklıkların zirve değerlerinde ve hız zirvelerinde karşılık gelen bir artışa neden olduğunu göstermektedir. CO ve kurum emisyonları sırasıyla %70 ve %43'ün üzerinde azalırken, yüksek yanma sıcaklıkları nedeniyle termal NOₓ emisyonlarında yaklaşık %85 artış görülmüştür. K-ε ve Rosseland modeli, incelenen koşullar altında türbülanslı karışma ve radyasyon kayıplarını en iyi şekilde temsil ettiği belirlenmiştir. Elde edilen sonuçlar ayrıca, %20 H2 karışımının CO ve kurumda neredeyse optimal bir azalma sağlarken, NOₓ'da kabul edilebilir bir artışa neden olduğunu ve bunun yanma verimliliğindeki artış ile emisyon dezavantajları arasında iyi bir denge sağladığını göstermektedir. Bu tezin sonuçları, motorlarda H2 benzin çift yakıt stratejileri için nicel göstergeler sunmakta ve ayrıca hesaplamalı akışkanlar dinamiği (HAD) tahminleri için doğru fiziksel modellerin seçimini ortaya koymaktadır.Conference Object Molecular Dynamics Study of the Thermal Conductivity of Graphene Coated Copper(Avestia Publishing, 2019) Toprak, Kasım; Ersavaş, GizemIn this study, the thermal conductivity of various size of pure copper, pure graphene and, different number of layer graphene coated copper models are studied using non-equilibrium molecular dynamics (NEMD) simulations. Our findings show that the thermal conductivity of graphene coated copper is higher than the uncoated ones. Furthermore, results also indicate that single layer graphene (SLG) model has the highest thermal conductivity as compared to the other model. Even though multiple layer graphene (MLG) has lower thermal conductivity value compare to SLG, this study shows that the thermal conductivity of MLG coated copper has higher thermal conductivity than SLG coated one. The most important finding in this study suggests that the thermal conductivity of copper can be improved using high thermal conductivity materials like graphene. © 2019, Avestia Publishing.Master Thesis Investigation of the Rotor Speed Impact on the Efficiency of Rotary Heat Recovery Ventilation Devices(Izmir Institute of Technology, 2018) Dilşen, Mustafa; Toprak, Kasım; Toksoy, MacitIn this study, the thermal efficiency of the rotary (regenerative) heat exchanger has been experimentally investigated in a heat recovery mechanical ventilation device. Beside impact of the same variable on pressure drop of the heat exchanger has been researched. Experiments have been carried out in a laboratory which belongs to a company manufactures heat recovery ventilation devices. The rotor has been tested within a commercial ventilation device rather than being tested alone in order to realize the actual conditions. Test results have also been compared with mathematical model results calculated with respect to the equations according to the literature research. NTU (number of transfer units) method has been used to calculate the thermal efficiency by using the various relevant equations which had been previously proposed by various researchers. The efficiency equation, which had a good agreement with the experimental results, has been determined by evaluating this comparison as a conclusion. Keywords and Phrases: heat transfer, heat recovery, energy recovery, ventilation, mechanical ventilation, regenerative heat exchanger, rotary heat exchanger (rotary wheel), thermal efficiency, thermal effectiveness, pressure drop.Article Citation - WoS: 6Citation - Scopus: 5Effect of Storage Tanks on Solar-Powered Absorption Chiller Cooling System Performance(Wiley, 2020) Toprak, Kasım; Ouedraogo, Kiswendsida EliasThermal storage, low power tariff at night, and low nocturnal temperature can be used in synergy to reduce the cooling costs of the solar-powered absorption chiller cooling systems. This study aims to reduce the required cooling capacity of an absorption chiller (ACH) powered by a solar parabolic trough collector (PTC) and a backup fuel boiler by integrating thermal storage tanks. The thermal performance of the system is simulated for a building that is cooled for 14 h/day. The system uses 1000 m(2) PTC with 1020 kW ACH. Chilled water storage (CHWS) and cooling water storage (CWS) effects on the system performance for different operation hours per day of the ACH under Izmir (Turkey) and Phoenix (USA) weather conditions are analyzed. When the ACH operates 14 h/day as the load for both systems and both locations, the variations of the solar collector efficiency and the cooling load to heat input ratio remain less than 4% after the modifications. From the addition of CHWS to the reference system, a parametric study consisting of changing the ACH operation hours per day shows that the required cooling capacity of the ACH can be reduced to 34%. The capacity factor of the ACH is improved from its reference value of 41% up to 96%.Article Citation - WoS: 2Citation - Scopus: 2Longitudinal Thermal Conductivity of Cu-Swcnt Core-Shell Nanowire: Molecular Dynamics Simulations(Begell House inc, 2023) Toprak, Kasim; Bayazitoglu, YildizThe phonon thermal conductivity of copper core and armchair single-walled carbon nanotube shell (Cu-SWCNT) coaxial nanostructure is presented using the non-equilibrium molecular dynamics (NEMD) simulations method. The study aims to investigate how the ultrathin Cu nanowire affects the thermal conductivity of Cu-SWCNT. The results have revealed that the thermal conductivity of Cu-SWCNT is more than two orders of magnitude higher than that of the Cu core with the contribution of the SWCNT shell. The influences of length, chirality, defect, and core filling on the thermal conductivity of Cu-SWCNT are studied using the two most used C-C potentials, the AIREBO and Tersoff potentials. The bare SWCNT and Cu-SWCNT simulation results revealed that the thermal conductivity using the AIREBO potential is lower than that of Tersoff. Although the thermal conductivity increases with the length of the coaxial tube, it decreases with the chirality and the filling ratio. Increasing the chirality of SWCNT and the Cu core-filling ratio can boost the core copper's contributions to the thermal conductivity, reducing the overall thermal conductivity. The lengths of the thermostat and buffer regions do not significantly affect the thermal conductivity. In addition, the vacancy concentration in heat flow regions effectively reduces thermal conductivity, whereas the vacancy in the thermostat regions does not have a significant effect. The thermal rectification factor defined as changing the imposed heat flux direction is up to 1.73% for the Cu-SWCNT and 2.63% for the SWCNT.Master Thesis Thermal Performance of Graphene Coating on Copper(Izmir Institute of Technology, 2019) Ersavaş, Gizem; Toprak, Kasım; Çelebi, Cem; Toprak, Kasım; Çelebi, CemOver heat is always a problem for electronic devices because the locally generated heat cannot be transferred appropriately to the corresponding heat sink fast enough. This situation leads to affect materials’ structures, mechanical properties and conductivities badly. In order to avoid this problem, high thermal conductivity materials are used to dissipate the heat quickly. Thanks to the development of technology, the size of the electronic devices is reduced day by day. This also shrinks the size of the interconnect components. So this situation leads to researchers to investigate nano-sized interconnect components and copper, which is a widely used material, is one of them. Copper is one of the preferred metals for electronic devices because of high thermal conductivity, easy processability, and high use in daily life and industry. For example, copper components, which is used in electronic, are getting so thin and must carry so much current. And that causes to increase friction. Thus heat is occurred. Consequently, cooling problems have arisen. And if the material’s cooling problem won’t be solved then the material can be damaged. It is thought that to overcome this problem, coating with a high thermal conductivity material such as graphene, the thermal conductivity can be improved. In this study, thermal performance of graphene-coated copper were investigated numerically and experimentally. This study consist of two main sections. The first part, MD simulation code was created using C++ programming language to investigate thermal conductivity of copper, different number of graphene layers and these graphene layers were coated on copper in different length, width, height and temperature. In the second part, the thermal performance of pure copper, annealed copper, a layer of graphene-coated copper, and multilayer graphene-coated copper was studied by the experimental setup at three different temperatures and volume flow rates.Article Citation - WoS: 3Citation - Scopus: 3Understanding Neural Network Tuned Langevin Thermostat Effect on Predicting Thermal Conductivity of Graphene-Coated Copper Using Nonequilibrium Molecular Dynamics Simulations(Iop Publishing Ltd, 2024) Toprak, KasimCopper has always been used in thermoelectric applications due to its extensive properties among metals. However, it requires further improving its heat transport performance at the nanosized applications by supporting another high thermal conductivity material. Herein, copper was coated with graphene, and the neural network fitting was employed for the nonequilibrium molecular dynamics simulations of graphene-coated copper nanomaterials to predict thermal conductivity. The Langevin thermostat that was tuned with a neural network fitting (NNF), which makes up the backbone of deep learning, generated the temperature difference between the two ends of the models. The NNF calibrated the Langevin thermostat damping constants that helped to control the temperatures precisely. The buffer and thermostat lengths were also analyzed, and they have considerable effects on the thermostat temperatures and a significant impact on the thermal conductivity of the graphene-coated copper. Regarding thermal conductivity, the four different shapes of vacancy defect concentrations and their locations in the graphene sheets were further investigated. The vacancy between the thermostats significantly decreases the thermal conductivity; however, the vacancy defect in thermostats does not have a similar effect. When the graphene is placed between two copper blocks, the thermal conductivity decreases drastically, and it continues to drop when the sine wave amplitude on the graphene sheet increases.Master Thesis Numerical and Experimental Investigation of Thermal Performance of Graphene Reinforced Aluminium(01. Izmir Institute of Technology, 2020) Yılmaz, Ahmet Berk; Toprak, Kasım; Kandemir, SinanGraphene is a material with superior properties such as high thermal conductivity and mechanical strength. These exceptional properties make graphene a good candidate for being used as a reinforcement agent in other materials. Aluminium is a widely used material in industry for thermal applications for being cheap, lightweight and having high thermal conductivity. In the literature, there are many examples of graphene reinforced aluminium production. Also, the effects of graphene on thermal conductivity and mechanical properties of aluminium are also investigated experimentally. However, there are limited molecular dynamics studies for graphene-aluminium composites. In this work, aluminium, graphene and graphene coated aluminium are modeled and simulated with non-equilibrium molecular dynamics method. Length, width, height, temperature dependence of thermal conductivity of these models are investigated. In addition, effects of graphene layer number, defect size and defect locations are also reported. Additionally, an experimental setup is designed and produced for a comparative study. Thermal performances of aluminium alloy and graphene nanoplatelet reinforced aluminium are investigated with a convection heat transfer test.