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Öğe Energy and exergy analyses of a fluidized bed coal combustor steam plant in textile industry(Elsevier Sci Ltd, 2016) Ozdil, N. Filiz Tumen; Tantekin, Atakan; Erbay, ZaferIn this study, the analyses of first and second laws of thermodynamic are presented for a 6.5 MW power plant located in Adana, Turkey. The system components, examined in the present study, are listed as a fluidized bed coal combustor (FBCC), a heat recovery steam generator (HRSG), an economizer (ECO), fans, pumps, a cyclone and a chimney. All of the system components are examined one by one and the energy and exergy analyses are carried out for all of the system components. The highest value of irreversibility is observed in the FBCC, about 93% of the entire system irreversibility tracked by HRSG and ECO with 3% and 1%, respectively. The high excess air value, which is the primary origin of irreversibility, causes the heat losses from the FBCC, due to the increment in mass flow rate of the combustion gas. Moreover, the high excess air value gives rise to occurrence of low combustion efficiency in FBCC which can be decreased through decreasing flow rate of air with decreasing oxygen. Secondly, changes in the energy and exergy efficiencies are examined employing different ambient temperature. As the ambient temperature increases, the second law efficiencies of FBCC and HRSG increases but efficiency of ECO decreases. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Energy and exergy assessment of a cogeneration system in food industry: a case study(Inderscience Enterprises Ltd, 2016) Ozdil, N. Filiz Tumen; Pekdur, ArzuIn this paper, extensive analysis of the first and second laws of the thermodynamic is performed for a 14.25 MW cogeneration system, located in Adana, Turkey. Energy demand of the consumer is around 10.5 MW while the cogeneration system produces almost 1.35 times of the consumer requirement. The analysis results show that the largest irreversibility occurs in the boiler, which is 36% of the overall system irreversibility. Moreover, the economiser and chimney have further significant irreversibilities which are 34% and 25%, respectively. This paper also investigates the relationship between the steam pressure at the boiler output and system efficiency. As the steam pressure at the boiler output increases, the exergy destruction of the boiler decreases; therefore, the efficiency of the boiler increases. In addition, there is a satisfactory combustion efficiency in this cogeneration system since there exists high molar fraction value of CO2 at the chimney output.Öğe Exergy and exergoeconomic assessments of an electricity production system in a running wastewater treatment plant(Pergamon-Elsevier Science Ltd, 2016) Ozdil, N. Filiz Tumen; Tantekin, AtakanThis study aims at presenting a detailed exergy and exergoeconomic analyses of a biogas engine powered electricity production system in a wastewater treatment plant located in Adana, Turkey. The overall system consists of a compressor, a turbine, a pump, four heat exchangers and a gas engine. The effect of the each system component on the exergy efficiency and exergoeconomic parameters is analyzed separately. The analysis indicates that major exergy destruction happens in the gas engine as 4055.31 kW, followed by the exhaust gas heat exchanger (EGHE) and lubrication oil heat exchanger (LOHE) as 99.86 kW and 92.64 kW, respectively. The second law efficiency of the compressor, turbine, pump, BGHE, LOHE, WHE, EGHE and gas engine are found as 76.50%, 78.43%, 6.49%, 13.40%, 11.56%, 60.44%, 67.36%, and 50.79%, respectively. The operating and maintenance costs, capital investment cost and total cost of the system are reckoned as 14.74 US$/h, 13.90 US$/h, and 28.64 US$/h, respectively to point out the exergoeconomic performance. The unit exergy cost and exergy cost of the fuel, which feeds the compressor, are reckoned as 4.88 US$/GJ and 141.12 US$/h. The exergy cost and electricity production unit exergy cost in the turbine are found as 4.87 US$/h and 11.32 US$/GJ. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Flow comparison around horizontal single and tandem cylinders at different immersion elevations(Pergamon-Elsevier Science Ltd, 2019) Ozdil, N. Filiz Tumen; Akilli, HuseyinFlow characteristic around a horizontal cylinder and tandem horizontal cylinders were compared in shallow water of which height was kept constant as h(w) = 60 nun in this study. The other parameters, taken constant, were free stream velocity and diameter of circular cylinders of which values were U =167 mm/s and D = 30 mm, respectively. To evaluate the time-averaged and instantaneous velocity vector area in the wake zone at Reynolds number; Re-D = 5000 basis on the diameter of cylinder, Particle Image Velocimetry (PIV) was operated. The gap (L) between the tandem cylinders was enhanced from 0 until 90 mm through 15 mm enhancements and it was enhanced from 90 up to 150 mm through 30 nun enhancements in order to observe effect of the gap on flow characteristics. Moreover, another important parameter was the submersion level that ranged from 7.5 until 60 mm through 7.5 mm increments (h(D)/D = 0.25-2) during the experiments. Five hundred instantaneous images were used in order to obtain Reynolds stress correlation, corresponding streamline topology and the mean velocity vector field. The investigation represented that the alternative cylinder attenuates the dimension of the wake zone in accordance with L/D = 0 location. The wake zone obviously happens between tandem cylinders at the starting of L/D =1 location. When the space between tandem cylinders deepens the dimension of the wake zone rises.Öğe Flow investigation of circular cylinder having different cavities in shallow water(Elsevier Science Inc, 2021) Tantekin, Atakan; Ozdil, N. Filiz Tumen; Akilli, Huseyin; Caliskan, MeltemThe control of the unsteady flow structure formed behind a cylinder placed horizontally in shallow water was analyzed experimentally using bare cylinder and cylinders with cavities having square and rectangular geometries, respectively. Reynolds number, Froude number and water height had been chosen as 5000, 0.27 and 90 mm, respectively and also these parameters were kept constant for all experiments. To consider the influence of height (h), the cylinder level was located at various heights from h: 0 mm to 60 mm. Furthermore, cavity angle (a) had been selected from 0 degrees, 80 degrees, 85 degrees, 90 degrees and 95 degrees to consider influence of cavity angle on flow. With the help of Particle Image Velocimetry (PIV), average velocity vectors were measured in two dimensions at many points simultaneously in a planar flow area. The results uncovered that large negative counter was observed at h: 37.5 mm in bare cylinder as well as cylinders having square and rectangular cavities at h: 45 mm. Also, no negative counter was observed for cylinders having rectangular cavity at h: 0 mm and a: 90 degrees and 95 degrees due to the bottom effect. Due to surface effects, a foci point was formed in all cylinders where close to the surface and close to the base. Two foci points and a saddle point were seen as they moved away from the surface for all cylinders. Also, the smallest vortex region was observed for cylinders having rectangular cavity at h: 37.5 mm and a: 90 degrees and 95 degrees in whole cylinders. Also, the highest drag coefficient (Cd) value was obtained for cylinder having square cavity at h: 52.5 mm and a: 80 degrees while the highest drag coefficient value was obtained for cylinder having rectangular cavity at h: 37.5 mm and a: 95 degrees.Öğe Investigation of flow characteristics for triangular grooved shape cylinder at different heights in shallow water(Pergamon-Elsevier Science Ltd, 2021) Caliskan, Meltem; Tantekin, Atakan; Ozdil, N. Filiz Tumen; Akilli, HuseyinThis study is an investigation and comparison of the flow characteristic around triangular grooved and bare cylinders, positioned horizontally in shallow water using Particle Image Velocimetry (PIV). Throughout the experiment, Reynolds number, Froude number and water height have been selected as 5000, 0.27 and 90 mm, respectively. To observe the effect of height (h) on the flow structure, cylinder is positioned at h: 0 mm, 15 mm, 22.5 mm, 30 mm, 37.5 mm, 45 mm, 52.5 mm and 60 mm. Moreover, grooved angle (a) has been changed from 0 degrees, 80 degrees, 85 degrees, 90 degrees and 95 degrees in shallow water to investigate the effect of grooved angle. The results show that the vortex forms vary according to the groove angle. It is seen that the vortex, the cylinders especially positioned at h: 0 mm and h: 60 mm, are affected owing to the surface and bottom effect. Furthermore, the largest Reynolds stress is observed at the h: 37.5 mm while the largest wake region is observed at the h: 52.5 mm. Also, the maximum Drag Coefficient (C-d) and Turbulence Kinetic Energy (TKE) are observed at h: 0 mm, a: 90 degrees for grooved cylinder and at h: 37.5 mm for bare cylinder, respectively.Öğe Investigation of flow structure around a horizontal cylinder at different elevations in shallow water(Pergamon-Elsevier Science Ltd, 2015) Ozdil, N. Filiz Tumen; Akilli, HuseyinFlow characteristics around a horizontal circular cylinder were investigated in shallow water. The diameter of circular cylinder, the height of shallow water and free stream velocity were kept constant during the experiments as D=30 mm, h(w)=60 mm and U=167 mm/s, respectively. Particle Image Velocimetry (PIV) was used to measure instantaneous and time-averaged velocity vector fields in the near wake region. In order to investigate the effect of immersion, the cylinder was placed at eight different elevations (h(p)) between bottom and free surface (from 7.5 to 60 mm with 7.5 mm increments). Instantaneous and time-averaged velocity vector field, corresponding streamline patterns and Reynolds stress correlation were used to analyze the behavior of the flow downstream of horizontal cylinder. The mean velocity vector field, corresponding streamline topology and Reynolds stress correlation were obtained using 500 instantaneous images. As the immersion level ratio (h(D)/D) increases, the magnitude of jet-like flow velocity goes up ranged from h(D)/D=0.25-1. Time averaged flow characteristics show that there is a difference between primary and developing circulation bubble depending on direction of rotation. This occurrence causes the entrainment and this stimulates the momentum transfer between the core and wake flow region for h(D)/D=1 and 2 cases. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Investigation of the effect of the water phase in the evaporator inlet on economic performance for an Organic Rankine Cycle (ORC) based on industrial data(Pergamon-Elsevier Science Ltd, 2016) Ozdil, N. Filiz Tumen; Segmen, M. RidvanIn this paper, exergoeconomic analysis of an Organic Rankine Cycle (ORC) is presented for a local power plant, located in the southern part of Turkey. Specific Exergy Costing Method (SPECOM) is applied using balance and auxiliary equations for the exergoeconomic analysis. The capital investment cost, operating and maintenance costs, and total investment cost of ORC steam plant are calculated as 7.43 $/h, 6.69 $/h and 14.12 $/h, respectively. The unit exergy cost and exergy cost of the electricity produced by the turbine are found as 11.05 $/GJ and 14.96 $/h, respectively. In order to show the effect of the water phase in the evaporator inlet on economic performance of the system, exergoeconomic factor of the system is calculated for four different water phases. When the evaporator inlet phase is in saturated liquid form, better exergoeconomic performance is observed for the system. The highest exergoeconomic factor is observed in the pump because of the lowest exergy destruction rate and low total investment cost, while the lowest exergoeconomic factor is observed in the evaporator due to the highest exergy destruction rate in the evaporator. Moreover, payback period assessment is calculated as 3.27 years for the ORC power plant. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Thermodynamic analysis of an Organic Rankine Cycle (ORC) based on industrial data(Pergamon-Elsevier Science Ltd, 2015) Ozdil, N. Filiz Tumen; Segmen, M. Ridvan; Tantekin, AtakanIn this study, thermodynamic analysis of an Organic Rankine Cycle (ORC) is presented in a local power plant that is located southern of Turkey. The system that is analyzed includes an evaporator, a turbine, a condenser, a pump and a generator as components. System components are analyzed separately using actual plant data and performance cycle. The relationship between pinch point and exergy efficiency is observed. As the pinch point temperature decreases, the exergy efficiency increases due to low exergy destruction rate. The energy and exergy efficiencies of the ORC are calculated as 9.96% and 47.22%, respectively for saturated liquid form which is the real condition. In order to show the effect of the water phase of the evaporator inlet, exergy destruction and exergy efficiencies of components and overall system are calculated for different water phases. The exergy efficiency of the ORC is calculated as 41.04% for water mixture form which has quality 0.3. On the other hand, it is found as 40.29% for water mixture form which has quality 0.7. Lastly, it is calculated as 39.95% for saturated vapor form. Moreover, exergy destruction rates of the system are 520.01 kW for saturated liquid form, 598.39 kW for water mixture form which has quality 0.3, 609.5 kW for water mixture form which has quality 0.7 and 614.63 kW for saturated vapor form. The analyses show that evaporator has important effect on the system efficiency in terms of exergy rate. The evaporator is investigated particularly in order to improve the performance of the overall system. (C) 2015 Elsevier Ltd. All rights reserved.