---

The performance of a cogeneration cycle with various working fluids is investigated and optimized with an economic approach. Exergy and exergoeconomic models are developed to investigate the thermodynamic performance of the cycle, and to assess the cost of products. In this study, the dynamic model would be registered to search the system behavior during a day. In this study, hydrogen production rate optimal design (HPROD) refrigeration power optimal design (RPOD) and cost optimal design (COD) are considered for analysis and optimization. According to recent parametric studies, boiler, turbine and condensation temperature and turbine inlet pressure affect the unit cost of products significantly. The results show the carbon dioxide and n-octane has a better operation to produce of hydrogen and refrigeration power among other working fluids, respectively. It is observed that, in carbon dioxide cycle, the SUCP is decreased by 8.5% when hydrogen production rate is decreased from 1.811 lit/s to 1.757 lit/s, therefore, in n-octane cycle, SUCP is decreased by 47.4% when refrigeration power is decreased from 9.599 KW to 6.622 KW. The evaluation of exergy destruction demonstrates in which the condenser has the highest exergy destruction, therefore, its rate in COD case is the lowest among the three other states. The results indicate, in carbon dioxide and n-octane cycles, the total exergy destruction and the investment cost rates in the RPOD case is higher than any other cases.

---

In this study, at first the combined steam and organic Rankine cycles, have been stimulated with high-temperature wasted hot gases recovery, from the energy and exergoeconomic points of view. In the configuration of the combined cycles, the high-temperature wasted gases acts as the source of steam cycle evaporator, then the decreased temperature exhaust gas of the steam cycle evaporator, is used as the low temperature source of organic cycle evaporator. Afterward the effects of changing different parameters such as temperature of the evaporator and condenser of steam cycle and pinch temperature difference, on the amount of total output work, total irreversibility, energy efficiency, exergy efficiency and exergoeconomic variables have been checked. The results in base state show that, energy and exergy efficiency of combined cycles are 0.2782 and 0.5279 respectively and the amount of output work and total irreversibility are 71401kW and 43616kW respectively. Total exergoeconomic factor for the combined cycles is 12.47 percent, which represents a high exergy destruction in components and recommends raising the initial cost of components in order to improve the performance of system. The evaporator, turbine and condenser of steam cycle, are the components that should be considered from the perspective of the exergoeconomic, because they contains the maximum amount of total initial costs and the cost of exergy destruction.

---

In this research, ammonia-water regenerative Rankine cycle driven by solar energy and LNG as it’s heat sink in condenser, is simulated from the energy, exergy and exergoeconomic point of view. A relatively new method is used to implement pinch temperature difference in heat exchangers which causes improving of the thermodynamic performance and output power of the system. Also heat exchangers are simulated by using heat transfer correlations of shell and tube heat exchanger in details. The results of based condition showed the suitable performance of natural gas cycle from the thermodynamic and exergoeconomic point of view and notifies the importance of using the natural gas cycle. Solar collector and condenser of ammonia-water cycle because of their high cost value, are introducing as the components that shoud be more concidered from the exergoeconomic viewpoint. The parametric analysis results show that in high inlet pressure of ammonia-water turbine, the exergy efficiency and the total cost of the system heve more suitable values while the net output power of the system decreases. Also by changing the ammonia mass fraction, changing of output parameters has a complicated patern. Finally by increasing the pinch temperature difference in heat exchangers, the decreased amount of system’s thermodynamic performance is more than the amount of system’s economical performance improvement.

---

In recent years, the importance and requirements for high-quality energy and water has been increased significantly, and this trend will strongly continue. One of the promising solution for the water scarcity's problem is desalination of the oceans salt water by thermal methods, and if the required thermal energy is provided by wastes of a thermal power plant it will be competitive with other methods. In this paper, a combined cycle including solid oxide fuel cell (SOFC) and gas turbine is used as thermal resource. Here, combination of these two systems beside of multi effect desalination (MED) system leads to reduce in energy consumption, pollutant emissions, investment and operation and maintenance cost, as well as increase of efficiency in comparison with the conventional individual systems. Exergetic and economic analysis using a computer program in EES software was performed. The results proposed a system with thermal and exergy efficiency of 60 % and 57%, respectively. The system expenditures and revenues were estimated, and the effect of two important design parameters, i.e. operational temperature and current density of fuel cell, on exergy efficiency and levelized cost of electricity were investigated. Consequently, the reliability and availability of the proposed system are calculated as 0.842, using the Markov method. It is seen after reliability analysis and availability calculation the exergy and energy efficiency is reduced and LCOE increased by 8.8%.

---

In this paper, the performance of a new design cogeneration cycle with various working fluids is investigated. Exergoeconomic and exergoenvironmental approach are developed to study the thermodynamic performance of the cycle and to assess the total cost of products. The naval design is based on organic Rankine cycle by using the gas turbine prime mover for fulfilling of the main goals of gas comperessor station of Nar-Kangan zone (South of Iran). These goals as follows: production of electricity and refrigeration power (cooling requirement) and total cost of products. According to recent parametric studies, boiler, turbine and condensation temperature and turbine inlet pressure significantly affect the three goals. The results show that dichlorotrifluoroethane (R-123) and toluene have a better performance in producing electricity (1.612MW) and refrigeration power (6.282MW) among other working fluids, while, the carbon dioxide has a better operation to reduce of products cost (103.5$/MJ). So, when the condensation temperature increases the refrigeration power decreases and boiler inlet temperature increases, the refrigeration power decreases. The results reveal that the refrigeration power decreases as the turbine temperatures and pressure increase and condensation temperature decreases; however, there is an optimum turbine inlet pressure (12MPa) in the carbon dioxide cycle for a minimum cost of products. The combustion chamber and boiler have a maximum destruction exergy rate for irreversibility and temperature difference among of system components

---

In recent years, the use of Gas Turbine-Modular Helium Reactor (GT-MHR) which operates in accordance with closed Brayton cycle with helium fluid as working fluid has attracted researchers’ attention because of its high efficiency, high reactor safety, being economical, and low maintenance costs. In the present study, a combined system, including GT-MHR cycle, Kalina cycle and Ammonia-water absorption cycle is investigated with respect to energy, exergy, and exergoeconomic. As the bottoming cycle, Kalina cycle and absorption cycle are used in order to avoid energy wasted by gas turbine cycle and to increase efficiency of energy conversion. The results of the simulated model show that, in the basic input mode, the overall work is 304462 kW, the overall exergy destruction is 289766kW and the overall exergy efficeincy of cogeneration cycle is 0.689kW. Also reactor, turbine and compressor in helium cycle are the component to which more attention should be paid with respect to exergoeconomic because the highest amount of cost rate is related to these components. At the end, parametric analysis is carried out in order to evaluate the effect of the changing pressure ratio of helium compressor, input temperature of helium compressor, input pressure and temperature of turbine and mass fraction of the base mode of the Kalina cycle on the output parameters.

---

In this article, a new power, cooling and heating cogeneration system consisting of a solid oxide fuel cell (SOFC) - gas turbine (GT), a heat recovery steam generator (HRSG), Generator-Absorber-heat eXchange (GAX) absorption refrigeration cycle and a heat exchanger for heat recovery (HR) has been studied from a thermodynamic and economic perspective. The modeling of this cycle was done by solving the electrochemical, thermodynamic and exergoeconomic equations for fuel cell and system components, simultaneously. The results showed that the exergy of our proposed combined cycle is 14.9% more and the irreversibility rate of this cycle is 10.6% less than that of the combined SOFC-GT-GAX systems in the same conditions. Also, the fuel cell and the afterburner have the highest rate of exergy destruction among other components due to irreversibility. Exergoeconomic analysis showed that the sum of uint cost of products (SUCP), the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system is equal to 331.1 $/GJ, 29.3%, 10.47 $/h and 25.32 $/h, respectively. Parametric studies showed that increasing the current density will increase the net electrical power, heating capacity of HRSG and HR heat exchanger, cooling capacity and total irreversibility. Also, with increasing of the current density, both the exergy efficiency and SUCP decrease.

---

---