Yazar "Abdulvahitoglu, Asli" seçeneğine göre listele

Listeleniyor 1 - 8 / 8
  • [ X ]
    Öğe
    A Comprehensive Analysis of Apricot Drying Methods via Multi-Criteria Decision Making Techniques
    (Wiley, 2024) Abdulvahitoglu, Asli; Abdulvahitoglu, Adnan; Cengiz, Nurten
    Food and food safety have been among the most important issues for people throughout history. Societies have always tried to be self-sufficient in food and have avoided becoming dependent on foreign sources. However, the fact that most foods are seasonal and the increasing population's food consumption have revealed the need to preserve foodstuffs for a long time. The old and well-known method used today for extending shelf life is the drying process. The drying process is preferred over other preservation methods for reasons such as being more economical, easier to transport, having a longer shelf life, more concentrated nutritional value, and containing fewer additives. This ensures that dried foods are of higher quality in terms of physical, chemical, microbial properties, and nutritional values compared to other packaged foods. While the drying process was traditionally done over a long period, technological advancements have led to the production of higher quality and more valuable commercial products in a shorter time. In this study, traditional and technological methods used in drying apricots were compared according to the parameters determined by experts in the field. Since multiple parameters are effective in the comparison, Multi-Criteria Decision Making (MCDM) techniques were used. The optimum apricot drying method was determined by combining the results obtained from different MCDM techniques with the Borda rule.
  • [ X ]
    Öğe
    A new approach for enhancing the effectiveness of a regenerative heat exchanger by using organic and inorganic phase change material
    (Springer, 2024) Kılıç, Mustafa; Sahin, Mahir; Abdulvahitoglu, Asli
    The increasing need for energy, along with limiting resources, has encouraged the development of novel solutions in the fields of energy conservation and storage. Phase change materials (PCMs), which are differentiated by properties such as large energy storage capacities, chemical stability, and reactivity to reduced working temperatures, play an important role in addressing the need for energy conservation. The goal of this research is to identify the heat transfer properties of various organic and inorganic phase change materials, compare their performance under certain working situations, and assure their maximum efficiency. The study undertakes a numerical analysis of the heat transfer performance of diverse organic (RT31, RT50) and inorganic (SP31, SP50) phase change materials across varying Reynolds numbers (Re = 500, 1000, 1500, 2000) under laminar conditions within a regenerative double-pipe heat exchanger. The outcomes reveal that SP31 demonstrates a 16% higher heat transfer effectiveness than RT31, while SP50 surpasses RT50 by 18% in terms of heat transfer effectiveness. As the Reynolds number increases, so does the heat transfer effectiveness, total heat transfer coefficient, and number of transfer units (NTU) for all types of phase change materials, but the capacity ratio decreases. Notably, inorganic phase change materials exhibit superior heat transfer performance compared to their organic counterparts. The results obtained from this study have been evaluated to be potentially useful for enhancing energy efficiency and system performance in systems operating at low-temperature ranges by utilizing phase change materials in heat exchangers under specified flow conditions.Please check the edit made in the article title.
  • [ X ]
    Öğe
    A new approach for selecting the most suitable oilseed for biodiesel production; the integrated AHP-TOPSIS method
    (Elsevier, 2022) Abdulvahitoglu, Asli; Kılıç, Mustafa
    The rapid growth of the world's population and industrial revolution has led to an increase in the need for energy. However, the scarcity of fossil fuels and serious environmental pollution problems have attracted researchers on developing alternative or renewable energy sources. Among these energy sources, biodie-sel has been the most popular energy source for decades. Energy crops that are cultivated as oil feedstock such as soybean, cottonseed, rapeseed, and camelina for biodiesel production in Turkey. Due to different physicochemical properties of these oilseeds, fuel quality, engine performance characteristics and emis-sion results of biodiesel are the significant criteria that have been changing. Therefore, these criteria were evaluated by using multi-criteria decision making (MCDM) techniques for the selection of the most suit-able energy crop. For this purpose, AHP has been applied for evaluating the significance of each criterion and ranks of investigated alternatives have been calculated by using TOPSIS. The results identified rape-seed as the most suitable oilseed as an energy crop for cultivation in Turkey whereas cottonseed was an unsuitable choice for biodiesel production. This integrated analysis method here can be utilized by pol-icymakers as a pre-investment tool in developing new business models for the goal of reducing exhaust emissions as well as decreasing dependence on fossil fuels. (c) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Ain Shams Uni-versity. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
  • [ X ]
    Öğe
    Evaluation of municipal solid waste options in Turkey: Scenarios for energy recovery, carbon mitigation and consequent financial strategies
    (Elsevier, 2019) Yilmaz, Ibrahim Halil; Abdulvahitoglu, Asli
    Solid waste management is a challenging issue in Turkey not only due to population and economic growths but its adverse environmental impact, financial problems and technological obstacles, as well. The detailed evaluation of solid waste options is significant not to end up with issues such as shutting down the plants and stopping the investments which may cause serious environmental problems as a result of uncontrolled landfill gas emissions. This research presents a theoretical model for energy recovery from the municipal solid waste (MSW) in Turkey, and the consequent carbon mitigation scenarios and financial strategies regarding the adoption of European Union acquis, respectively. The model predicts the population growth compatible with the baseline scenario of Turkish Statistical Institute data and the MSW generation for each city of Turkey between 2004-2043. The three scenarios, namely open dump, landfill and incineration, are taken into consideration for greenhouse gas (GHG) emissions, energy recovery from emissions and economics subject to the Turkish environmental regulations towards the progress of this adoption. The aim of the research is to fulfill the literature gap by proposing practical formulations and realistic models for the mentioned scenarios and considering the energy, economy and ecology nexus based on the regional characteristics of solid waste systems as a consequence of adapting the Turkish MSW regulations and management. Results show that the maximum potential of electricity production is estimated to be 3461-13,450 GW h (0.40-1.56 GW/annum) in the landfill scenario while it is 1572-8386 GW h (0.17-0.96 GW/annum) in the incineration scenario. According to the nationwide projections, Turkey will have consumed the electricity of 437 TW h and 2236 TW h by 2023 and 2043, respectively. While the landfill scenario would meet 0.40-1.40% and 0.15-0.60% of the nationwide electricity production for the interested years, respectively; the incineration scenario would supply 0.06-0.34% and 0.07-0.38% of the nationwide electricity consumption. The maximum total savings for the landfill and incineration scenarios would range from 35.2-66.7 and 32.7-64.5 billion $, respectively in a time horizon at which the total amount of wastes for the corresponding scenarios are equivalent to each other. It is stressed that the landfill scenario would be better for lowering the GHG emissions in case of proper emission control.
  • [ X ]
    Öğe
    Evaluation of watermelon seed biodiesel as an alternative fuel in diesel engines
    (Gazi Univ, Fac Engineering Architecture, 2017) Abdulvahitoglu, Asli; Tuccar, Gokhan
    The exiguity of oil forces scientists to investigate new energy resources and biodiesel became one of the most popular alternative fuel since it can be obtained from renewable sources. The aim of this study is to evaluate availability of watermelon seed oil biodiesel (WMB) in diesel engines as alternative fuel. In this work, some physical fuel properties of obtained WMB and its blend with diesel fuel from %20 to %80 by volume (WMB20) were tested. The measured fuel property values were density, cetane number, viscosity, pour point and flash point. In addition, test fuels were utilized in a diesel engine in order to evaluate effect of WMB usage on engine performance parameters and exhaust emissions such as nitrogen oxides and carbon monoxide. According to engine performance experiments results; although both torque and brake power values of the test engine were slightly decreased, emission values were improved with WMB utilization. Therefore, the ester of water melon seed oil is advised to be a suitable alternative fuel additive to diesel fuel with its environmental friendly combustion profile.
  • [ X ]
    Öğe
    Integrated analytic hierarchy process and multi-criteria decision-making approach: An Application for Unmanned Underwater Vehicle Control Method Selection
    (Pergamon-Elsevier Science Ltd, 2024) Nennioglu, Ahmet Kemal; Abdulvahitoglu, Asli; Dal, Abdurrahim
    Using Multi-Criteria Decision Analysis (MCDA) techniques, it is possible to thoroughly examine all available options and determine the most desirable ones. However, the prevalence of these methods, which employ various computational changes, can result in disparate outcomes. Therefore, the final rankings should be as dependable and consistent as possible. In this study, the consistency of the findings obtained from the TOPSIS, COPRAS, MAUT, and MOOSRA methodologies was investigated in the real-world problem of Unmanned Underwater Vehicle Control Method Selection by forming decision matrices through simulations.
  • [ X ]
    Öğe
    NUMERICAL INVESTIGATION OF HEAT TRANSFER AT A RECTANGULAR CHANNEL WITH COMBINED EFFECT OF NANOFLUIDS AND SWIRLING JETS IN A VEHICLE RADIATOR
    (Vinca Inst Nuclear Sci, 2019) Kılıç, Mustafa; Abdulvahitoglu, Asli
    The present study is focused on the numerical investigation of heat transfer from a heated surface by using swirling jets and nanofluids. Consequences of discrete Reynolds number, inlet configuration and types of nanofluids (pure water, Al2O3-H2O, Cu-H2O, and TiO2-H2O) were studied numerically on heat transfer and fluid-flow. As a base coolant Al2O3-H2O nanofluid was chosen for all parameters. So, a numerical analysis was done by using a k-. turbulent model of PHOENICS CFD code. It is determined that increasing Reynolds number from Re = 12000-21000 causes an increment of 51.3% on average Nusselt Number. Using 1-jet causes an increase of 91.6% and 29.8% on average Nusselt number according to the channel flow and 2-jet. Using Cu-H2O nanofluid causes an increase of 3.6%, 7.6%, and 8.5% on the average Nusselt number with respect to TiO2-H2O, Al2O3-H2O and pure water.
  • [ X ]
    Öğe
    USING ANALYTIC HIERARCHY PROCESS FOR EVALUATING DIFFERENT TYPES OF NANOFLUIDS FOR ENGINE COOLING SYSTEMS
    (Vinca Inst Nuclear Sci, 2019) Abdulvahitoglu, Asli
    The radiator is an important heat exchanger for cooling the engine. Usually, water and ethylene glycol are used in vehicles as cooling fluids. However, these fluids have lower thermal conductivity. In the automotive industry, coolants with better characteristics are being searched to develop more efficient engines. In recent years, nanofluids have become more attractive to car manufacturers, with higher thermal conductivity to increase heat transfer. In this study, the analytic hierarchy process is used to structure the decision problem and to attribute weights to criteria. Three types of nanofluid (Cu-water, NiO-water, and CuO-water) were evaluated. Among the thermophysical properties of nanofluid, the most important one is calculated as the thermal conductivity and also the Cu-water is determined as the most suitable coolant in terms of thermophysical properties among the evaluated nanofluid.