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Öğe BİNA DIŞ DUVARLARINDA YOĞUŞMA DİKKATE ALINARAK GEREKLİ YALITIM KALINLIĞININ BELİRLENMESİ: BİTLİS İLİ İÇİN ÖRNEK ÇALIŞMA(2018) Bademlioğlu, Ali Hüsnü; Canbolat, Ahmet Serhan; Kaynaklı, ÖmerTürkiye gibi dış ortam sıcaklıklarının geniş bir aralıkta değişkenlik gösterdiği ülkelerdeki binalarda, kış aylarında ısı kayıplarını, yaz aylarında ise ısı kazançlarını azaltmak için yapılan yalıtım uygulamalarının önemi her geçen gün artmaktadır. Yapılan yalıtım uygulamalarında su buharı hareketlerinin göz önüne alınması yoğuşma riski açısından oldukça önemlidir. Yoğuşma veya terleme olarak adlandırılan bu olay, malzemelerin zarar görmesi, mukavemetin azalması ve toplam ısı transfer katsayısının yükselmesi nedeniyle ısı kayıplarının artması gibi istenmeyen sonuçlar doğurur. Bu çalışmada dıştan yalıtımlı duvar tipi seçilmiş ve Bitlis ili için yapılan yalıtım uygulamasında yoğuşma riski dikkate alınarak, aylara göre gerekli minimum yalıtım kalınlıkları hesaplanmıştır. Yoğuşma riskinin en fazla olduğu ve bu nedenle yoğuşmayı önlemek için gereken yalıtım kalınlığının maksimum olduğu ay olarak şubat ayı belirlenmiştir. Yapı elemanındaki ısı ve kütle transferi hesaplamaları, farklı iç ortam sıcaklıkları ve bağıl nem koşulları için yapılmıştır. Belirlenen çalışma şartlarında, şubat ayı için gerekli minimum yalıtım kalınlığı yaklaşık 0,104 m olarak hesaplanmıştır.Öğe THE EFFECT OF WATER VAPOR DIFFUSION RESISTANCE FACTOR OF INSULATION MATERIALS FOR OUTER WALLS ON CONDENSATION(2018) Bademlioğlu, Ali Hüsnü; Kaynaklı, Ömer; Yamankaradeniz, NurettinCondensation, which is the result of water vapor diffusion, affects the heat transfer in the building material negatively. The condensation which is seen mostly in winter seasons at building materials, occurs when the surface temperature of the building material in contact with air falls below the raw temperature of the air. In this case, condensed water may cause mildew, fungal growth, odors, and deterioration of dye and building materials or adversely affected thermal insulation on the walls. Materials used for thermal insulation in buildings constitute resistance against water vapor diffusion. Water vapor diffusion resistance factor (VDRF) of materials can vary over a wide range. In this study, considering VDRF range that is commonly encountered in insulation applications, the effect of VDRF of insulation materials on condensation within constructions, and on the minimum thickness of insulation required to prevent this condensation accordingly were examined. Externally insulated wall was taken as sample wall model, heat and mass transfer calculations from wall unit area and insulation thickness minimization were performed for different indooroutdoor temperatures and relative humidity values. As a result of the analysis conducted, in constant indoor-outdoor conditions in general, as VDRF increases, the risk of condensation inside the wall first decreases and then increases. Minimum insulation thickness that is required to be applied to prevent condensation also shows a similar trend depending on the VDRF. For constant VDRF, it was come to the conclusion that as the difference between indooroutdoor temperatures and relative humidity increases, the risk of condensation and consequently required insulation thickness increases.Öğe A PARAMETRIC ANALYSIS OF THE PERFORMANCE OF ORGANIC RANKINE CYCLE WITH HEAT RECOVERY EXCHANGER AND ITS STATISTICAL EVALUATION(2019) Bademlioğlu, Ali Hüsnü; Canbolat, Ahmet Serhan; Yamankaradeniz, Nurettin; Kaynaklı, ÖmerIn this study, the performance of a case study of Organic Rankine Cycle with heat recovery exchanger using different fluids is analyzed. As the fluids worked in the cycle, the commonly used R134a, R236fa, R245fa, R600a, R717 and R718 are preferred. Cycle performances of the selected fluids are compared based on both the heat source’s temperature that changes between 80°C and 109°C and the effectiveness of the heat exchanger. Furthermore, the contribution ratios and the order of importance of the parameters affecting the performance of the cycle are evaluated using the Taguchi statistical method. As a result, the effect of the waste-heat source temperature on the performance of the system is greater than the other parameters examined, and the contribution ratio of this parameter is determined as 59.80%. However, effectiveness of heat exchanger is found to be the least effective parameter and the effect ratio is calculated as 2.18%. In addition, the best and worst operating conditions are determined from the statistical analysis, and in these conditions, the thermal efficiencies of the Organic Rankine Cycle are obtained as 15.26% and 8.61%, respectivelyÖğe Determination of Optimum Insulation Thickness for Different Insulation Applications Considering Condensation(Univ Osijek, Tech Fac, 2018) Kaynakli, Omer; Bademlioğlu, Ali Hüsnü; Ufat, Hande TufekciIn this study, thermal insulation thickness used in the outer walls of buildings composing of different insulation applications having the same thermal resistance was optimized by considering condensation. The minimum insulation thickness required to prevent condensation (i.e. optimum insulation thickness) in building structural component was determined. Heat and mass transfer calculations within the structural component were performed with respect to various indoor-outdoor temperature and relative humidity values and results were given in graphs. It was observed that optimum insulation thickness is generally increased with an increase in the indoor temperature, indoor relative humidity and outdoor relative humidity. It was concluded that type of insulation application does not significantly affect optimum insulation thickness at low and medium level (Theta<0.60) indoor relative humidity conditions. It was also observed that externally insulated wall application generally yields better results at high indoor and outdoor relative humidity conditions.Öğe Performance Assessments of Organic Rankine Cycle With Internal Heat Exchanger Based on Exergetic Approach(Asme, 2018) Yamankaradeniz, Nurettin; Bademlioğlu, Ali Hüsnü; Kaynakli, OmerThis study makes energy and exergy analysis of a sample organic Rankine cycle (ORC) with a heat exchanger which produces energy via a geothermal source with a temperature of 140 degrees C. R600a is preferred as refrigerant to be used in the cycle. The changes in exergy destructions (of irreversibility) and exergy efficiencies in each cycle element are calculated in the analyses made based on the effectiveness of heat exchanger used in cycle and evaporator temperature changing between 60 and 120 degrees C for fixed pinch point temperature differences in evaporator and condenser. Parameters showing system performance are assessed via second law approach. Effectiveness of heat exchanger and temperature of evaporator are taken into consideration within the scope of this study, and energy and exergy efficiencies of cycle are enhanced maximum 6.87% and 6.21% respectively. Similarly, exergy efficiencies of evaporator, heat exchanger, and condenser are increased 4%, 82%, and 1.57%, respectively, depending on the effectiveness of heat exchanger and temperature of evaporator.Öğe Investigation of parameters affecting Organic Rankine Cycle efficiency by using Taguchi and ANOVA methods(Pergamon-Elsevier Science Ltd, 2018) Bademlioğlu, Ali Hüsnü; Canbolat, A. S.; Yamankaradeniz, N.; Kaynakli, O.There are many factors affecting the Organic Rankine Cycle's (ORC) performance, such as working fluid selection, evaporator and condenser temperatures, pinch point temperature differences (the minimum temperature difference between refrigerant and the waste heat source (PPTDevap) or cooling water (PPTDcon)), superheating temperature, heat exchanger effectiveness, and isentropic efficiencies of the turbine and pump. In this study, the parameters' impact weights on the cycle's efficiency are discussed and comparatively examined based on the statistical analyses. First, the system's thermodynamic model was established, and variation of the cycle's thermal efficiency was calculated for different parameters and their different ranges. Next, to obtain the contribution ratios and the order of importance of these parameters, the thermodynamic analysis results were evaluated using two statistical methods: Taguchi and ANOVA. In conclusion, the evaporator and condenser temperature and the turbine efficiency have a large effect on the thermal efficiency of the ORC, and the total impact ratio of these parameters is determined as approximately 70%. However, PFTDevap, PPTDcon and pump efficiency are found to be the least effective parameters. In addition, the best and the worst operating conditions are determined from the statistical analysis and in these operating conditions, the thermal efficiencies of the ORC are obtained as 18.1% and 9.6%, respectively.Öğe EXERGY ANALYSIS OF THE ORGANIC RANKINE CYCLE BASED ON THE PINCH POINT TEMPERATURE DIFFERENCE(Yildiz Technical Univ, 2019) Bademlioğlu, Ali Hüsnü; Yamankaradeniz, R.; Kaynakli, O.Organic Rankine Cycle (ORC) is a system that uses working fluids with hydrocarbon components instead of water and generates power from the heat recovery of different heat sources. In this study, the exergy analysis of a simple ORC, which produces electrical energy with the help a geothermal source (125 degrees C), was performed. R123, R152a, R245fa and R600a were determined as the fluids to be used in the Cycle. In this analysis, which was carried out according to the pinch point temperature differences (5-20 degrees C) in the evaporator, the exergy performance of the cycle components was evaluated for the geothermal resource unit flow rate and the variation of the exergy efficiency of the system was calculated. With the increase of the pinch point temperature difference in the evaporator, the decrease of the system's exergy efficiency became maximal (11.7%) with the use of R152a as a refrigerant and the loss in the system's exergy efficiency became minimal (9.03%) with the use of R123 as a refrigerant.Öğe Performance optimization of absorption refrigeration systems using Taguchi, ANOVA and Grey Relational Analysis methods(Elsevier Sci Ltd, 2019) Canbolat, A. S.; Bademlioğlu, Ali Hüsnü; Arslanoglu, N.; Kaynakli, O.There are various factors having an impact on the energetic and exergetic performance (i.e., COP and eCOP) of an absorption refrigeration systems (ARS) such as the temperatures of the generator, condenser, evaporator and absorber, effectiveness of solution, refrigerant and solution-refrigerant heat exchangers and isentropic efficiency of the solution pump. Many studies have focused on these process parameters, but the importance order and contribution ratios of the parameters due to thermodynamic performance have not been determined by using statistical methods. Firstly, in this study, cycles' thermodynamic model is established and the variation of the COP and eCOP are calculated for different working conditions with different parameters ranges. The effects of these parameters on the COP and eCOP are examined separately on a statistical basis. The importance order of the parameters are determined by using Taguchi and ANOVA methods and the results are compared. Optimum operating conditions are determined by means of statistical analysis for the COP and eCOP. Under these operating conditions, the COP and eCOP of the system are calculated as 0.697 and 0.2829, respectively. Furthermore, for the simultaneous maximization of these two performance indicators, Taguchi-Grey Relational Analysis (GRA) is used. By using this analysis, importance order of the examined parameters on multiple performance characteristics are determined. The absorber and evaporator temperatures are the most efficient parameters on multiple performance characteristics with a contribution ratio of 29.66% and 26.34% of the total effect while the least efficient parameters are the pump efficiency and effectiveness of solution refrigerant heat exchanger with a contribution ratio of 0.48% and 2.41%, respectively. For the best condition considering the multiple performance characteristics, COP and eCOP of the system are found as 0.6255 and 0.2829, respectively. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Numerical simulation of a parabolic trough collector containing a novel parabolic reflector with varying focal length(Pergamon-Elsevier Science Ltd, 2019) Külahlı, Mehmet Canalp; Akbulut Özen, Songül; Etemoglu, Akin BurakIn this study, a novel parabolic reflector for a Parabolic Trough Collector (PTC) is presented. The reflector contains a varying focal length in lengthwise direction while still maintaining a fixed focal line. Due to this geometry, heat flux around the absorber not only varies circumferentially but also axially. A new geometric design parameter is defined which is the ratio of focal length at the ends, and the effects of it on the thermal behavior are investigated numerically. To represent the heat flux realistically a method is presented by employing a custom code to construct the novel reflector in SolTrace (a ray tracing software), and heat flux profile around the absorber is calculated. This flux is applied to a Computational Fluid Dynamics (CFD) model as a source term and simulations are realized. The coupled model is validated with the experimental results regarding the LS-2 module. Besides the parametric analyses about geometric factor, flow rate optimization analyses are also. As a result of the parametric analyses, a 0.21% rise is achieved for thermal efficiency and a 0.63% increase is achieved for net energy gain as a result of the flow rate optimization study.Öğe A modeling of electricity generation by using geothermal assisted organic Rankine cycle with internal heat recovery(Taylor & Francis Inc, 2019) Canbolat, A. S.; Bademlioğlu, Ali Hüsnü; Kaynakli, O.In this study, the performance of organic Rankine cycle (ORC), which produces electrical energy, was examined by using a geothermal resource with a temperature of 145 degrees C. The fluids used in the system were determined as dry type fluids, and R142b, R227ea, R245fa, R600, and R600a were preferred as a working fluid. Within the scope of this study, energy and exergy analysis of the system was performed for different evaporator pressures (1000-2000 kPa). With the help of these analyses, the performances of the cycle elements were examined and the first and second law efficiencies of the system were compared for different refrigerants. Considering the selection of refrigerant, and evaporator pressure within the scope of this study, the first and second law efficiencies of the cycle have enhanced maximum of 4.86% and 19.78%, respectively.Öğe Multi-objective optimization of parameters affecting Organic Rankine Cycle performance characteristics with Taguchi-Grey Relational Analysis(Pergamon-Elsevier Science Ltd, 2020) Bademlioğlu, Ali Hüsnü; Canbolat, A. S.; Kaynakli, O.In the literature, energetic and exergetic performance of Organic Rankine Cycle (ORC) were investigated by various researchers. The working parameters affecting the cycle's performance were determined but the impact weights and the order of importance of these parameters were not discussed with a statistical approach. In this context, nine fundamental process parameters such as working fluid type, pinch point temperature differences in the evaporator and condenser, superheating temperature, evaporation and condensation temperatures, heat exchanger effectiveness, turbine and pump efficiencies have been selected for the statistical evaluation. A comprehensive statistical analysis has been carried out to observe the effect of the parameters on the first and second law efficiencies of the ORC. The impact ratios and order of importance of these parameters on the system's performance indicators have been determined. While Taguchi method is performed to determine the optimum levels of each parameter, ANOVA method is used to obtain the impact weights of the parameters on objective functions. In addition to these methods, Grey Relational Analysis (GRA) method is used to optimize the multi-objective function. Evaporator temperature, turbine efficiency, effectiveness of heat exchanger, condenser temperature are obtained as main process parameters on the multiple performance characteristics of ORC and the impact ratios of these parameters are calculated as 31.37%, 19.53%, 16.64%, and 16.61%, respectively. The best condition for the multiple performance characteristics is determined as A(1)B(1)C(3)D(3)E(3)F(3)G(1)H(3)I(3) and under these operating conditions, the first and second law efficiencies of the system are found as 18.1% and 65.52%, respectively.Öğe Solar photovoltaic source based magnetic launcher simulation design with thermal requirements consideration(Pergamon-Elsevier Science Ltd, 2020) Özküçük, Serhat; Külahlı, Mehmet CanalpSolar photovoltaic source based military defense systems, especially magnetic launchers, have significant advantages in terms of source independence, mobility, and efficiency. In this study, a solar photovoltaic sourced magnetic launcher system is modeled, and a critical component of the system's (launcher coil) thermal requirements are analyzed. The designed system contains four energy conversion steps that are respectively photon, electrical, magnetic, and mechanical energy; also the launcher coil has an energy loss by the form of heat. Solar photovoltaic source based magnetic launcher system is sourced by solar photovoltaic panels and produced electrical energy is filtered, limited, and stored by an electrical converter. Stabilized electrical energy is converted to the magnetic energy by a coil. This magnetic energy is transferred to the projectile as mechanical energy. The microcontroller in the electrical converter unit controls all processes and manages the switching operations. Designed launcher coil is subject to a high amplitude current and employs simple, low-cost materials as an air core and copper wire. For this reason, the insulation breakdown on the launcher coil due to high temperatures are investigated, and a simple cooling configuration is suggested. (C) 2019 Elsevier Ltd. All rights reserved.Öğe INVESTIGATION OF PARAMETERS AFFECTING THE OPTIMUM THERMAL INSULATION THICKNESS FOR BUILDINGS IN HOT AND COLD CLIMATES(Vinca Inst Nuclear Sci, 2020) Canbolat, Ahmet Serhan; Bademlioğlu, Ali Hüsnü; Saka, Kenan; Kaynakli, OmerThis paper investigates the factors affecting the optimum insulation thickness and its pay-back period, such as heating and cooling energy requirements of building, lifetime, present worth factor, costs of insulation material and installation, costs of energy sources for heating and cooling, heating and cooling system efficiencies, and solar radiation. For this purpose, by considering two cities characterizing the hot and cold climatic conditions, the optimum insulation thickness and its payback period have been calculated and a detailed parametric analysis has been carried out. To achieve practical results, the ranges of the parameters considered in the study include the values typically reported in the literature. The variations in the optimum insulation thickness and the pay-back period with all parameters are presented in graphical form. Finally, order of importance and contribution ratios of the examined parameters on the optimum insulation thickness are determined with the help of Taguchi method. It is found that heating degree-days is the most efficient parameter on the optimum insulation thickness with an impact ratio of 27.33% of the total effect while the least efficient parameter is the efficiency of heating system with an impact ratio of 3.21%.Öğe Isolated solar electronic unit design including capacitive storage for the uninterruptible power supply of critical DC loads(Pergamon-Elsevier Science Ltd, 2021) Özküçük, Serhat; Akbulut Özen, SongülIn this study, to the aim was to design an isolated, reliable and efficient DC-DC (flyback based) photovoltaic energy sourced supply unit, which has its own electrolyte-super capacitor based energy storage unit in order to compensate for disruptions and failures that can occur in photovoltaic solar panels. In this storage unit, a hierarchical charging structure has been developed for eliminating the drawbacks of battery technologies such as cooling issues, chemical dangers, heavy weight, charging and discharging current/voltage limitations. The designed supply unit is capable of operating in a wide range of input voltages for the supply of important and expensive solar-based photovoltaic subsystems. Also, it was designed to supply a steady and balanced power to control systems that have microcontrollers or expensive control elements for different purposes up to 50 W. The design can be considered as a model for an uninterruptible power supply with a specific capacitive storage. The designed unit has important advantages due to its large usage area, especially microgrid and off-grid systems, its low cost and less complex construction. The designed hierarchical charging super capacitor based energy storage unit in this study is expected to have important implications for future research due to its possibility to be developed in accordance with different environmental conditions and objectives.
