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- Katipoğlu, Okan Mert(57)
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Yayınlar
- Book ChapterYalnız künye2018Thermodynamic performance assessment and comparison of active magnetic regenerative and conventional refrigeration systems
Ganjehsarabi, Hadi; Dincer, Ibrahim; Gungor, Ali; Aloui, F; Dincer, I
Comprehensive thermodynamic analyses, performance assessments, and comparative evaluations of active magnetic regenerative (AMR) and conventional vapor-compression-based refrigeration systems are presented in this study. The active magnetic regenerative (AMR) uses a magnetic material as a thermal storage medium and as a refrigerating medium. A parametric analysis is to investigate the influences of various operating conditions and/or parameters on the thermodynamic performance of the AMR cycle. In this regard, these performance results are compared with the published experimental data for a traditional refrigeration system with the same refrigeration capacity and temperature span. The results of this particular study show that the COP of the AMR cycle changes very little with varying hot source temperature. It is shown that the conventional vapor-compression-based refrigeration cycles offer better performance than the active magnetic regenerative refrigeration systems.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Thermoeconomic modeling and multi-objective evolutionary-based optimization of a modified transcritical CO2 refrigeration cycle
Khanmohammadi, Saber; Goodarzi, Mohsen; Khanmohammadi, Shoaib; Ganjehsarabi, Hadi
In this study, thermoeconomic optimization is applied to a modified transcritical (CO2) refrigeration cycle. Modified cycle includes an extraction of saturated vapor as a coolant stream from the separator feed to the intercooler. In order to perform multi criteria optimization two objective functions consist of cooling capacity and annual cost rate are chosen. Gas cooler temperature (Tgc), gas cooler pressure (Pgc), extraction mass flow rate (α) and evaporator temperature (Tev) are selected as decision variables based on parametric study. The thermodynamic and economic modeling of the system is performed. To determine analytical, objective functions GMDH (group method of data handling) neural network method is used and finally with a developed code in Matlab optimal values of decision variables have been obtained. In addition, to better understanding the change of decision variables in optimum point, the scatter distribution of these variables is carried out.
RDL Kalıcı Kaydıİncele - Book ChapterYalnız künye2018Investigation of an optimal operating condition for a micro combustor regarding basic thermophotovoltaic system requirements
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker; Nizetic, S; Papadopoulos, A
In this study, effects of equivalence ratio and thermal power on combustion and emission behaviour of premixed hydrogen air mixtures were numerically investigated by constructing 3D micro combustor models. Combustion behaviour was analysed by examining combustor outer wall and centreline temperature profiles, and convective and radiative heat transfer quantities. Besides, emission behaviour was analysed in terms of centreline NOx profiles and NOx amounts emanated from exhaust of the micro combustor. Regarding these, optimal operating condition with respect to combustion performance and pollutant emissions was investigated by varying thermal power and equivalence ratio. Turbulence model used in this study is RNG k-ε (Yilmaz et al. Int J Hydrog Energy 42:25744–25755, 2017). Multistep combustion reaction process with 9 species and 19 steps was simulated using Eddy dissipation concept model. Data obtained from this study was validated against published experimental data (Tang et al. Int J Hydrog Energy 40:2396–2403, 2015). Results showed that optimal operating condition can be gained at 0.8 equivalence ratio and 1200 ml/min hydrogen flux.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Prediction of diffuse solar radiation using satellite data
Bakirci, Kadir; Kirtiloglu, Yusuf
In the project of the solar systems, the values of the solar radiation of a region must be known. The global solar radiation measurements are performed by the Turkish Meteorological Service in Turkey, while the diffuse solar radiation measurements are unavailable. In this study, some new models for predicting the monthly average daily diffuse solar radiation on a horizontal surface for Erzincan, Turkey are developed using satellite data. The evaluation of the models is carried out with the statistical analysis methods of mean bias error (MBE), root mean square error (RMSE) and correlation coefficient (r). The results are proved that the correlation equations obtained in here can be used to forecast diffuse solar radiation reasonably well.
RDL Kalıcı Kaydıİncele - Book ChapterYalnız künye2018Numerical simulation of building wall integrated with phase change material: A case study of a Mediterranean City Izmir, Turkey
Asker, Mustafa; Alptekin, Ersin; Tokuç, Ayça; Ezan, Mehmet Akif; Ganjehsarabi, Hadi; Nizetic, S; Papadopoulos, A
Nowadays, improving the energy efficiency of buildings without decreasing the comfort of its occupants is of great importance in the whole world. The most widespread passive energy control strategy is the utilization of insulation materials with low thermal transmittance. This chapter proposes an alternative control strategy that would help to create more stable temperatures inside a room. This is changing the thermal capacity of a common wall with the integration of phase change material (PCM). To evaluate the performance of the PCM, user-defined scripts are coded in commercial CFD solver ANSYS FLUENT to simulate one-dimensional heat transfer through a wall within a detached cabin in a city with Mediterranean climate for 1 day in the hot season. The placement and amount of PCM in the building element are changed and analyzed. The results show a decrease in the indoor wall temperature up to 6 °C, which is promising for further research.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2017Exergoeconomic analysis and multi objective optimization of a solar based integrated energy system for hydrogen production
Khanmohammadi, S.; Heidarnejad, P.; Javani, N.; Ganjehsarabi, H.
In the current study, an integrated renewable based energy system consisting of a solar flat plate collector is employed to generate electricity while providing cooling load and hydrogen. A parametric study is carried out in order to determine the main design parameters and their effects on the objective functions of the system. The outlet temperature of generator, inlet temperature to organic Rankine cycle turbine, solar irradiation intensity (I), collector mass flow rate (m˙col) and flat plate collector area (AP) are considered as five decision variables. The results of parametric study show that the variation of collector mass flow rate between 3 kg/s and 8 kg/s has different effects on exergy efficiency and total cost rate of the system. In addition, the result shows that increment of inlet temperature to the ORC evaporator has a negative effect on cooling capacity of the system. It can lead to a decrease the cooling capacity from 44.29 kW to 22.6 kW, while the electricity generation and hydrogen production rate of the system increase. Therefore, a multi objective optimization is performed in order to introduce the optimal design conditions based on an evolutionary genetic algorithm. Optimization results show that exergy efficiency of the system can be enhanced from 1.72% to 3.2% and simultaneously the cost of the system can increase from 19.59 $/h to 22.28 $/h in optimal states.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2017A numerical study on combustion and emission characteristics of premixed hydrogen air flames
Cam, Omer; Yilmaz, Harun; Tangoz, Selim; Yilmaz, Ilker
Main challenges for micro power generators that utilize combustion process for energy production are inadequate residence time, destructive radical wall interactions and intensified heat loss which are mainly rooted from size limitation of such devices. To achieve high and uniform energy output, and bring in a solution to these challenges in an environment friendly manner without any kind of fundamental modification, effect of equivalence ratio on combustion and emission behavior of premixed hydrogen/air flames is numerically investigated in this study. For this purpose, an experimentally tested micro cylindrical combustor model is constructed and premixed hydrogen/air combustion in this model is simulated by varying equivalence ratio between 0.5 and 1.2 to find an optimal equivalence ratio with respect to drawbacks of micro power generators. Combustion and turbulence models implemented in this study are Eddy Dissipation Concept and Standard k-ε models, respectively. A detailed hydrogen/air reaction mechanism which consists of 9 species and 19 steps is employed to accurately gain insight into combustion process. Simulation results show that as the equivalence ratio decreases; centerline temperature distribution gets a lower value and the place where chemical reactions take place moves downstream. The most uniform temperature distribution is achieved between 0.8 and 1.0 equivalence ratios. The highest NOx formation is at 0.9 equivalence ratio and its mass fraction decreases sharply when the equivalence ratio reduces from 0.9 to 0.5.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2016Analysis and optimisation of a cascade active magnetic regenerative refrigeration system
Ganjehsarabi, Hadi; Dincer, Ibrahim; Gungor, Ali
In this paper, comprehensive thermodynamic analysis and optimisation of a cascade active magnetic regenerative refrigeration system are performed. A parametric study is conducted to investigate the effects of various design parameters on the cycle performance through energy and exergy efficiencies. A multi-objective optimisation method based on a fast and elitist non-dominated sorting genetic algorithm is applied to determine the best design parameters for the system. Two objective functions utilised in the optimisation study are the total cost rate of the system and the system exergy efficiency. The total cost rate of the system is minimised while the cycle exergy efficiency is maximised using an evolutionary algorithm. To provide insight, the Pareto frontier is shown for a multi-objective optimisation. The results show that exergy efficiency could be increased by 14.53% using exergy-based optimisation and the cost could be reduced by 12% using the cost-based optimisation.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2016Energy and exergy analyses of a solar assisted combined power and cooling cycle
Ganjehsarabi, Hadi; Asker, Mustafa; Seyhan, Aslihan Kurnuc
In this study, a thermodynamic analysis of a solar assisted Rankine-Goswami integrated cycle is carried out for a range from 230 to 240 MW sizes. To illustrate the performance characteristics of these integrated cycle, an exergy analysis is conducted to pinpoint the losses due to internal and external irreversibilities of each component. In addition, the effect of design parameter such as condenser pressure on the performance of the integrated cycle is examined. The results shows that the variation of condenser pressure from 4 kPa to 24 kPa greatly reduces the exergy efficiency of the system. Moreover, it is found the exergy efficiency of standard solar assisted Rankine cycle case is 42.8% whereas the exergy efficiency of solar Rankine-Goswami multigeneration system is 47.03%.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2016Parametric optimization and exergetic analysis comparison of subcritical and supercritical organic Rankine cycle (ORC) for biogas fuelled combined heat and power (CHP) engine exhaust gas waste heat
Yağli, Hüseyin; Koç, Yildiz; Koç, Ali; Görgülü, Adnan; Tandiroğlu, Ahmet
In this paper, a subcritical and supercritical organic Rankine cycle (ORC) are designed to recover exhaust gas waste heat of biogas fuelled combined heat and power (CHP) engine. The CHP engine is located in Belgium and uses biogas as fuel which is produced from the digestion of domestic wastes by anaerobic digestion. R245fa is selected as working fluid. First, the system parameters as net power, mass flow rate, pumps total power consumption, total evaporator exergy inlet, thermal efficiency and exergy efficiency are improved by changing turbine inlet temperature and pressure. After which second low analysis of the overall system and system components are determined for the best performed subcritical and supercritical cycles. Compared with subcritical ORC, the supercritical ORC has shown better performance. The best performed cycle net power, thermal efficiency and exergy efficiency are evaluated as 79.23 KW, 15.51% and 27.20% for subcritical ORC and 81.52 kW, 15.93% and 27.76% for supercritical ORC, respectively.
RDL Kalıcı Kaydıİncele - Book ChapterYalnız künye2014Wind energy resource assessment of Ergan mountain ski center, Erzincan, Turkey
Tandıroğlu, Ahmet; Çetin, Murat
Ergan Mountain Ski Center is located in Erzincan, East Anatolian region of Turkey. It is 15 km south of the city and situated in the Mercan (Munzur) Mountain chain whose length is 200 km and width of between 15 and 45 km. Height of the Ergan is about 3,300 m. In this study, wind energy potential of Ergan Mountain Ski Center which is located in Erzincan, East Anatolian region of Turkey was investigated by analyzing wind speed data collected in ten minutes intervals by wind energy observation station situated at a height 2,350 m above sea level at 12 m above the ground. These measurements are performed from 2011 February to 2013 May. Wind energy potential of monitored area is determined by performing statistical analysis of collected data. Weibull distribution is used in the statistical analysis, and it is examined that the numerical values of shape and scale parameters for Ergan Mountain Ski Center varied over a wide range. The annual values of dimensionless Weibull shape parameter k ranged from 1.41 to 1.83 with a mean value of 1.71, while those of Weibull scale parameter c were in the range of 3.11–11.99 m/s with a yearly mean wind speed of 7.8 m/s. Results revealed that the highest and the lowest wind power potential is in March and October, respectively. Annual mean wind power density is obtained as 230.68 W/m2 inside the observatory field. The results show that the investigated location of Erzincan Ergan Mountain Ski Center has available wind energy potential and is feasible to establish wind power generation plant in a medium scale for installed power load of Erzincan Ergan Mountain Ski Center.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2012Performance of coupled novel triple glass and phase change material wall in the heating season: An experimental study
Kara, Yusuf Ali; Kurnuç, Aslihan
A Trombe wall that uses a phase change material (PCM) as the heat storage medium is usually called a PCM Trombe wall or PCM wall. A research project was conducted to investigate the performance of coupled novel triple glass (NTG) and PCM wall, which is simply called PCM wall in this paper, as a solar space heater. The south façade of a test room was constructed using PCM walls. Rubitherm® GR35 and GR41 were incorporated into the plaster of the walls as PCM. The ratio of the solar energy gain provided by the PCM walls to the heat load of the test room per month varied from 4% to 70%; daily overall efficiency of the PCM walls varied from 20% to 36%; and solar transmittance of the NTG varied from 0.45 to 0.55 during the heating period. The overall efficiency of the PCM wall including GR35 was higher than that of the PCM wall including GR41.
RDL Kalıcı Kaydıİncele - Conference ObjectYalnız künye2012The relation of collector and storage tank size in solar heating systems
Çomakli, Kemal; Çakir, Uǧur; Kaya, Mehmet; Bakirci, Kadir
The most popular method to benefit from the solar energy is to use solar water heating systems since it is one of the cheapest way to benefit from the solar energy. The investment cost of a solar water heating system is very low, and the maintenance costs are nearly zero. Using the solar energy for solar water heating (SWH) technology has been greatly improved during the past century. A storage tank is used in many solar water heating systems for the conservation of heat energy or hot water for use when some need it. In addition, domestic hot water consumption is strongly variable in many buildings. It depends on the geographical situation, also on the country customs, and of course on the type of building usage. Above all, it depends on the inhabitants' specific lifestyle. For that reason, to provide the hot water for consumption at the desirable temperature whenever inhabitants require it, there must be a good relevance between the collectors and storage tank. In this paper, the optimum sizes of the collectors and the storage tank are determined to design more economic and efficient solar water heating systems. A program has been developed and validated with the experimental study and environmental data. The environmental data were obtained through a whole year of operation for Erzurum, Turkey.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2009Emission characteristics of a converted diesel engine using ethanol as fuel
Çetin, Murat; Yüksel, Fikret; Kuş, Hüsamettin
The aim of this study is to investigate the suitability of neat ethanol (95%) as an alternative fuel in an engine converted from diesel to ethanol, and experimentally determine the effect of different main fuel jets at carburetor on engine exhaust emissions and fuel consumption at high engine compression ratio (CR) of 14. For this purpose, three different diameter main fuel jets (1.40 mm, 1.50 mm, 1.60 mm) were used for ethanol fuel tests in a naturally aspirated four-stroke pre-chamber diesel engine. Tests were made at full-load conditions at speeds between 1200 and 2600 rpm at intervals of 400 rpm. In addition, cold-start system was developed and engine could be operated at reliable idle speed and medium speed down to 0 °C ambient temperatures. The results show that HC emissions increase with increasing fuel jet diameter and CO, PM and HC emissions reduce significantly at idle speed and medium engine speeds.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2007The use of hazelnut oil as a fuel in pre-chamber diesel engine
Çetin, Murat; Yüksel, Fikret
This paper briefly reviews the use of hazelnut oil as an alternative fuel in pre-chamber diesel engines, and compares it with diesel fuel. In order to investigate the effects of the use of hazelnut oil as a diesel engine fuel, an experimental setup was constructed. The results showed that the hazelnut oil may be employed as a possible candidate for most diesel fuel operating conditions in terms of the performance and emission parameters without any modification and preheating of the fuels.
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