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Öğe Advanced exergy analysis of an integrated solid waste fueled cogeneration system based on organic Rankine Cycle for different working fluids(Pergamon-Elsevier Science Ltd, 2022) Ustaoglu, Abid; Torlakli, Hande; Ergun, Alper; Erdogmus, Ertugrul; Akay, Mehmet EminIn this study, the performance evaluation of an ORC-based solid waste-powered cogeneration system was carried out using conventional and advanced exergy analysis methods. Eight different working fluids including dry (isopentane, n-pentane, n-octane, n-heptane), isentropic (R141b, R123), and wet (methanol, water) types were selected for the evaluation. The total capacity of the heat source was determined with the data obtained from the assessment of municipal solid wastes with different calorific values by the characterization method. Energy and exergy analyses were carried out for each component to examine the effect of selected cycle parameters, including evaporator pressure, intermediate pressure, and condenser pressure, and determine the optimum working fluid for the system. The exergy destruction in the components was split into avoidable/unavoidable and endogenous/exogenous parts in the advanced exergy analysis to identify the improvement potentials and the interaction between the components. The thermal and exergy efficiency values reach the highest values of 81.36 % and 40.76 %, respectively. R141b performs as the best working fluid, while the lowest performance is obtained from water. About 121.3 kW of power generation and 918.2 kW of process heat were obtained from the ORC-CHP system using R141b at 1400 kPa evaporator pressure. Conventional exergy analysis states that the evap-orator, process heater, and turbine are the most critical components, accounting for 67.94 %, 19 %, and 4.92 % of the total exergy destruction rate, respectively. The advanced exergy analysis shows that the priority should be on the turbine having the largest share of the avoidable part. The avoidable part, which accounts for 14.5 % of the total exergy destruction, can be reduced by system improvements.Öğe Energetic, exergetic, and environmental evaluation of railway transportation by diesel and electric locomotives(Wiley, 2022) Akay, Mehmet Emin; Ustaoglu, AbidIt is critical to reveal the amount of energy and exergy-losses of a system along with environmental issues. This article aims to carry out energy, exergy, and environmental analyses in rail freight trains hauled by diesel and electric locomotives. This study is an important tool for policymakers and energy-planners to gain insight into the performance of the railway-sector, which is an important transportation way in Turkey. It should be a challenge for society and governmental institutions to decrease the losses and to improve the overall performance due to severe energy-problems. The overall energy-efficiency of diesel trains was calculated to be 29.1% as that of exergy-efficiency was 27.2% between 2005 and 2018. In the case of electric-trains, these became 43.4% for 2005-2018. The average overall energy and exergy efficiencies of the railway sector were calculated to be 30.94% and 29.3%, respectively. The results indicate that there is a significant improvement potential in the railway sector. The average carbon emissions of diesel and electric trains are 1.372 kgCO(2)/kWh and 1.346 kgCO(2)/kWh, respectively. The carbon emission of the electric trains per annual useful energy (kg-CO2/kWh) is comparatively high due to the electricity generation methods in the country.Öğe Enhanced exergy analysis of a waste heat powered ejector refrigeration system for different working fluids(Inderscience Enterprises Ltd, 2017) Ustaoglu, Abid; Alptekin, Mustafa; Akay, Mehmet Emin; Selbas, ResatConventional and enhanced exergy analyses of a waste heat powered ejector refrigeration system using exhausted gas from rotary kiln were carried out. Isentropic (R290, R141b and R142b), wet (R134a and R152a) and dry fluids (R600a) were considered in the cycle in terms of avoidable-unavoidable parts of the exergy destruction to decide improvement potentials of the overall system. The results indicate a significant issue; the importance of component can change regarding refrigerant. The ejector comes into view as an important component to improve the overall cycle performance for R134a while the generator shows the best improvement potential for R600a.Öğe Thermal and exergetic approach to wet type rotary kiln process and evaluation of waste heat powered ORC (Organic Rankine Cycle)(Pergamon-Elsevier Science Ltd, 2017) Ustaoglu, Abid; Alptekin, Mustafa; Akay, Mehmet EminIn this study, the energetic and exergetic performance analysis of a rotary kiln and cooling section in a cement factory using wet method was carried out based on the actual operational data. The energy and exergy efficiencies of the wet type rotary kiln are about 46% and 35%, respectively. The results showed that a great amount of heat energy of 30.5 MW is exhausted from the chimney of rotary kiln. In order to evaluate recovery capacity of exhausted gas, Organic Rankine Cycle (ORC) was considered and its energetic and exergetic performance were evaluated for isentropic and dry type fluids for different conditions. Isentropic fluid, R245fa shows the best performance while the dry fluid, R600a has the lowest performance. For condensation temperature of 303 K and evaporation pressure of 1500 kPa, the thermal and exergy efficiencies of R600a are 9.8% and 21.7% while the thermal and exergy efficiencies of R245fa are 13% and 29%, respectively. Isentropic fluids, R245fa, R142b can be used at high evaporator pressures and low condenser temperatures as R600 and R600a are not appropriate after a certain pressure since the efficiency remain stable. The exergy destruction rates in heat exchanger and evaporator are about 80% of the total exergy destruction. (C) 2016 Elsevier Ltd. All rights reserved.
