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Advanced exergy and exergo-economic analyses of a novel combined power system using the cold energy of liquefied natural gas
(Pergamon-Elsevier Science Ltd, 2022) Ozen, Dilek Nur; Kocak, Betul
In this study, a new combined power system using the cold energy of liquefied natural gas (LNG) is designed. Conventional and advanced exergy and exergo-economic analyses of the system were made. According to the research in the literature, for the first time, advanced exergo-economic analysis was applied to a combined power system using the cold energy of LNG with the Modified Productive Structure Analysis (MOPSA) method. 23% of the exergy destruction and exergy destruction cost rate of the combined system is avoidable. In both conventional and advanced exergy analysis, the highest exergy destruction and cost rate were found in the parabolic solar collector. In addition, as a result of the analyses, it has been seen that the most effective main system components with the potential to improve the performance of the combined system are the parabolic solar collector, the turbine in direct expansion cycle and the turbine in the Organic Rankine cycle, respectively. The study revealed that there is potential to improve the performance of the proposed combined power system.(c) 2022 Elsevier Ltd. All rights reserved.
Advanced exergy and exergo-economic analyses of an advanced adiabatic compressed air energy storage system
(Elsevier, 2022) Guleryuz, Esra Hancer; Ozen, Dilek Nur
It is important to determine the source of the exergy destruction of the system components and their relations with each other in order to increase the working performance of energy charging systems. In this paper, con-ventional/advanced exergy and exergo-economic analyses of an advanced adiabatic compressed air energy storage (AA-CAES) system with a power output of 10 MW were performed. The results show that the proposed system accounts for 44 % of the exergy destruction and 31 % of the exergy destruction cost avoidable while 10 % of investment cost is avoidable. These percentage values represent the improvement potential for the system. Conventional exergy analysis results show that three most effective system components in exergy destruction as wind turbine, regulator and heat exchanger-3, respectively, while this order changes as wind turbine, compressor-1 and turbine-2 in advanced exergy analysis. This difference is due to technological limitations. In summary, advanced exergy analysis provides the designer with a detailed path regarding the improvement potential and cost savings of the system.
Advanced exergy and exergo-economic analyses of an advanced adiabatic compressed air energy storage system, part 2: Parametric study and optimization
(Elsevier, 2023) Gueleryuez, Esra Hancer; Ozen, Dilek Nur; Acilar, Ayse Merve
In this study, parametric analysis and multi-objective optimization of the advanced adiabatic compressed air energy storage system (AA-CAES) were performed. Non-dominated Sorting Genetic Algorithm (NSGA-II) method was used in the multi-objective optimization study. In the optimization study, objective functions were determined in the conventional and advanced exergy/exergo-economic analyses concept. In the optimization study in the concept of advanced exergo-economic analyses, a new performance criterion that is not in the literature was determined and the results were confirmed by conventional exergo-economic analyses. In this study, the modified total unit product cost, which is given as the new performance criterion, is defined on the basis of avoidable feed exergy cost rate and avoidable investment cost rate. This shows the potential to be improved in the cost of the system and gives more detailed information than the total unit product cost in conventional exergo-economic analysis. As a result of the optimization study, the total unit product cost and the exergy efficiency of the system were found to be 162.9 $/day and 64.3%, respectively for the conventional exergy/exergoeconomic analyses concept. For the advanced exergy/exergo-economic analyses concept, the modified total unit product cost and the modified exergy efficiency of system were found to be 103.5 $/day and 91.9 %. The exergy efficiency and the total unit product cost improved by 16.48 % and 3.55 %, respectively, with the optimization study according to the basic case of the overall system. With the parametric study, the increase in the efficiency of the wind turbine affected the exergy destruction rate more than the other system components. While the effect of the increase in the efficiency of the turbines on the exergy destruction cost rate of the system is greater than the other system components, the system component that most affects the cost rate of the system is the compressors.
A comparative assessment of SPECO and MOPSA on costing of exergy destruction
(Inderscience Enterprises Ltd, 2020) Uysal, Cuneyt; Ozen, Dilek Nur; Kurt, Huseyin; Kwak, Ho Young
This paper presents the comparison of specific exergy costing (SPECO) and modified productive structure analysis (MOPSA) method to test their abilities on costing of exergy destruction. MOPSA method is applied to a combined supercritical CO(2)regenerative cycle and organic Rankine cycle using zeotropic mixtures for gas turbine waste heat recovery system. The results obtained with applying SPECO method to the system are taken from literature. The exergy destruction cost rate of overall system is obtained to be $86.08/h and $1,113.13/h for MOPSA and SPECO methods, respectively. The exergoeconomic factor of overall system is found to be 31.88% for SPECO method, while this value is found to be 85.82% for MOPSA method. The obtained results with applying MOPSA method for exergy destruction cost rate are significantly lower and more consistent compared to the results obtained by SPECO method.
A comparative assessment of SPECO and MOPSA on costing of exergy destruction
(Inderscience Enterprises Ltd, 2020) Uysal, Cuneyt; Ozen, Dilek Nur; Kurt, Huseyin; Kwak, Ho Young
This paper presents the comparison of specific exergy costing (SPECO) and modified productive structure analysis (MOPSA) method to test their abilities on costing of exergy destruction. MOPSA method is applied to a combined supercritical CO(2)regenerative cycle and organic Rankine cycle using zeotropic mixtures for gas turbine waste heat recovery system. The results obtained with applying SPECO method to the system are taken from literature. The exergy destruction cost rate of overall system is obtained to be $86.08/h and $1,113.13/h for MOPSA and SPECO methods, respectively. The exergoeconomic factor of overall system is found to be 31.88% for SPECO method, while this value is found to be 85.82% for MOPSA method. The obtained results with applying MOPSA method for exergy destruction cost rate are significantly lower and more consistent compared to the results obtained by SPECO method.
Effects of operation temperature and reactant gas humidity levels on performance of PEM fuel cells
(Pergamon-Elsevier Science Ltd, 2016) Ozen, Dilek Nur; Timurkutluk, Bora; Altinisik, Kemal
In this study, the effects of operation conditions on the performance of a polymer electrolyte membrane fuel cell are investigated and the results are presented together with a comprehensive literature review on the related topics. The cells with 25 cm(2) active area are tested for different inlet gas humidification levels and inlet temperatures, operating temperatures and oxidant type. The cells are characterized by the performance curves together with the cell resistance measurements. The results indicate that the humidification of the inlet gases positively affect the cell performance. However, the improvement in the cell performance is higher when the cathode gas is humidified. In addition, the operating temperature and the inlet gas temperatures are found to be the most significant parameters. The cell performance tends to increase significantly with increasing the operating and inlet gas temperatures. The effect of the oxidant type is also considered and the cell tested with pure oxygen shows slightly higher performance. (C) 2016 Elsevier Ltd. All rights reserved.
Energy, exergy, and exergo-economic analysis of a novel combined power system using the cold energy of liquified natural gas (LNG)
(Wiley, 2020) Ozen, Dilek Nur; Ucar, Ibrahim
This study proposed a novel combined power system that uses the cold energy of liquefied natural gas (LNG) for the BOTAS LNG receiving terminal located in Marmara Eregli in Turkey. In the proposed system, the main cycle was a Brayton cycle (BC), while the subcycles consisted of a supercritical CO2 cycle (S-CO2) and an organic Rankine cycle (ORC). The combined power system was analyzed based on energy, exergy, and exergo-economic. The effects of the determined decision variables (Compressor-II input temperature, Compressor-I-II and Turbine-I-III isentropic efficiencies, CO2 cycle pressure rate, Turbine-III input pressure, ORC pressure rate, and propane mass flow rate) on the exergo-economic performance of the system were discussed, and the optimal points of the system were found. The base state of the system that had operational conditions and assumed design inputs was compared to the working conditions that were determined as a result of optimization, and a cost reduction of 67% was calculated.
EXPERIMENTAL INVESTIGATION AND NUMERICAL MODELING OF THERMAL PERFORMANCE OF FIN-TUBE EVAPORATOR UNDER FROSTING CONDITIONS
(Turkish Soc Thermal Sciences Technology, 2014) Ozen, Dilek Nur; Altinisik, Kemal; Dincer, Kevser; Ates, Ali
Formation of frost in a heat exchanger reduces air passage area and lowers the performance of the heat exchanger due to the insulation effects it possesses. In this study, the performance of finned tube evaporator at transient regime was investigated both experimentally and numerically. When the experimentally obtained values of the evaporator's the total conductivity (UA) are compared with those obtained from the numerical model, it is found that they are very close to one another. On the numerical model, the effects of inlet air temperature, relative humidity and air velocity on evaporator's total conductivity (UA), air side pressure drop (Delta P-a) and frost thickness (delta(fst)), were respectively, studied. The results obtained from the numerical model show that Delta P-a and delta(fst) values increase with increasing air temperature and relative humidity while decreasing UA values.
Investigation of Performance of Heating and Cooling of Counter Flow Ranque-Hilsch Tubes with L/D=15, 16, 17, 18 for Brass
(Trans Tech Publications Ltd, 2013) Dincer, Kevser; Berber, Adnan; Ozen, Dilek Nur
In this study, heating and cooling performances of counter flow Ranque-Hilsch vortex tubes (RHVTs) were experimentally investigated for brass. The vortex tubes were made of brass. Diameter of vortex tube (D) was 10 mm. Length of vortex tube (L) was 15D, 16D, 17D and18D. The number of nozzles (Nn) was 5. The conical edges of the plugs have a slope of 30 degrees angle. Working pressure of Ranque-Hilsch was 460 kPa (absolute). According to the experimental results, the maximum heating performance of the RHVT system was found to be 39,5 degrees C at P-17 and the maximum cooling performance of the RHVT in this study was found to be -28,6 degrees C at P-18. An increase in fraction of cold flow (xi) led to a increase in the heating performance.
Rule-Based Mamdani-Type Fuzzy Modeling of Heating and Cooling Performances of Counter Flow Ranque-Hilsch Vortex Tubes with Different Geometric Construction for Brass
(Trans Tech Publications Ltd, 2013) Ozen, Dilek Nur; Berber, Adnan; Dincer, Kevser
In this study, thermal performances of counter flow Ranque-Hilsch vortex tubes were experimentally investigated and modeled with a Rule Based Mamdani-Type Fuzzy (RBMTF) modeling technique. The vortex tubes were made of brass. Diameter of vortex tube (D) was 10 mm. Length of vortex tube (L) was 10D, 11D, 12D, 13D, 14D. Input parameters (xi, L/D) and output parameters (Delta T-h, Delta T-c) were described by RBMTF if-then rules. 45 experimental data sets were used in the training step. R-2 for the Delta T-h was found to be 99.42 % and R-2 for the Delta T-c was 99.66 %. The actual values and RBMTF results demonstrated that RBMTF can be successfully used for the determination of heating and cooling performances of counter flow RHVT with different geometric constructions for brass.
Rule-based Mamdani-type fuzzy modeling of heating and cooling performances of counter-flow Ranque-Hilsch vortex tubes with different geometric construction for steel
(Pergamon-Elsevier Science Ltd, 2013) Berber, Adnan; Dincer, Kevser; Yilmaz, Yusuf; Ozen, Dilek Nur
In this study, heating and cooling performances of counter-flow Ranque-Hilsch vortex tubes (RHVT) were experimentally investigated and modeled with a RBMTF (Rule-Based Mamdani-Type Fuzzy) modeling technique. Input parameters (xi, L/D) and output parameters Delta T-h, Delta T-c were described by RBMTF if-then rules. 81 experimental data sets were used in the training step. Numerical parameters of input and output variables were fuzzificated as linguistic variables: Very Very Low (L1), Very Low (L2), Low (L3), Negative Medium (L4), Medium (L5), Positive Medium (L6), High (L7), Very High (L8) and Very Very High (L9) linguistic classes. R-2 for the Delta T-h was found to be 99.60% and R-2 for the Delta T-c was 99.80%. The actual values and RBMTF results indicated that RBMTF can be successfully used for the determination of heating and cooling performances of counter-flow RHVT with different geometric constructions for steel. (C) 2013 Elsevier Ltd. All rights reserved.
Rule-based Mamdani-type fuzzy modelling of thermal performance of fintube evaporator under frost conditions
(E D P Sciences, 2016) Ozen, Dilek Nur; Altinisik, Kemal; Dincer, Kevser; Ates, Ali; Sertkaya, Ahmet Ali; Tolu, Muhammed Emin
Frost formation brings about insulating effects over the surface of a heat exchanger and thereby deteriorating total heat transfer of the heat exchanger. In this study, a fin-tube evaporator is modeled by making use of Rule-based Mamdani-Type Fuzzy (RBMTF) logic where total heat transfer, air inlet temperature of 2 degrees C to 7 degrees C and four different fluid speed groups (ual=1; 1.44; 1.88 m s-1, ua2=2.32; 2.76 m s-1, ua3=3.2; 3.64 m s-1, ua4=4.08; 4.52; 4.96 m s-1) for the evaporator were taken into consideration. In the developed RBMTF system, outlet parameter UA was determined using inlet parameters Ta and ua. The RBMTF was trained and tested by using MATLAB (R) fuzzy logic toolbox. R-2 (%) for the training data and test data were found to be 99.91%. With this study, it has been shown that RBMTF model can be reliably used in determination of a total heat transfer of a fm-tube evaporator.
THERMOECONOMIC ANALYSIS OF T56 TURBOPROP ENGINE UNDER DIFFERENT LOAD CONDITIONS
(Turkish Soc Thermal Sciences Technology, 2020) Ozen, Dilek Nur; Uysal, Cuneyt; Balli, Ozgur
In this study, T56 turboprop engine was theoretically modelled for 75% load, 100% load, military (MIL) mode, and Take-off mode conditions. For each load conditions, thermoeconomic analyses of T56 turboprop engine were performed to allocate the unit costs of shaft work and thrust and to determine exergy destruction cost rates for system equipment. In thermoeconomic analyses, Specific Exergy Costing (SPECO) and Modified Productive Structure Analysis (MOPSA) methods were used. MOPSA method gave higher unit cost values for shaft work and thrust compared to SPECO method. As a result, for Take-off mode, the unit cost of shaft work transferred to propeller was determined to be 78.87 $/GJ in SPECO method, while this value was calculated to be 84.68 $/GJ with MOPSA method. The unit cost of negentropy of T56 turboprop engine decreased with increasing in engine load and ranged from 14.98 $/GJ to 11.08 $/GJ. The exergy destruction cost rates obtained with MOPSA method for the system equipment were considerably lower than the results obtained with SPECO method. For instance, in Take-off mode, exergy destruction cost rate of combustion chamber was calculated to be 865.10 $/h in SPECO method, whereas it was calculated to be 247.94 $/h in MOPSA method. The exergoeconomic factor of overall system was determined to be 23.07% in SPECO method, and 54.16% in MOP SA method for Take-off mode.

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