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Abstract A new formulation for the evaporation, flashing, condensation processes taking place in the effects of thermal desalination systems which simulates the operation of both forward and parallel/cross configurations is coupled with an exergo-economic model based on the SPECO method. The thermo-economic model uses accurate properties for the seawater, brine, pure water and vapour and is solved with an equation solver which does not require the development of a specific solution algorithm as in most previous studies. This flexible model is used to analyze the influence of the number of effects N and the temperature difference ΔT e between effects on the technical and economic performance of multi-effect desalination systems with ejector vapour compression. In particular, it is shown that the performance calculated by an earlier black-box approach is not attainable by technically and economically realistic systems. It is also shown that for each feed configuration and a given number of effects there exists an optimum value of ΔT e which minimizes the cost of the produced potable water. This last result forms the basis of a procedure that combines black-box results with the optimum value of ΔT e and can be used to select the appropriate system for any specific application.

Abstract A new formulation for the evaporation, flashing, condensation processes taking place in the effects of thermal desalination systems which simulates the operation of both forward and parallel/cross configurations is coupled with an exergo-economic model based on the SPECO method. The thermo-economic model uses accurate properties for the seawater, brine, pure water and vapour and is solved with an equation solver which does not require the development of a specific solution algorithm as in most previous studies. This flexible model is used to analyze the influence of the number of effects N and the temperature difference ΔT e between effects on the technical and economic performance of multi-effect desalination systems with ejector vapour compression. In particular, it is shown that the performance calculated by an earlier black-box approach is not attainable by technically and economically realistic systems. It is also shown that for each feed configuration and a given number of effects there exists an optimum value of ΔT e which minimizes the cost of the produced potable water. This last result forms the basis of a procedure that combines black-box results with the optimum value of ΔT e and can be used to select the appropriate system for any specific application.

Abstract Clamping mechanisms have significant effect on the performance of polymer electrolyte membrane (PEM) fuel cells. In this paper, PEM fuel cell with new clamping mechanism is designed to study the contact pressure distribution over the active area of PEM fuel cell's membrane electrode assembly (MEA). The clamping pressure is pneumatically exerted on the PEM fuel cell assembly. A comparison between the conventional and new clamping mechanism is carried out with simulation, and the numerical results are validated against experimental investigation performed in the fuel cell technology research laboratory. The experimental results are gathered using embedded pressure measurement films in the designed single cell. The results achieved via finite element method are in good agreement with experimental results. It is concluded that the contact pressure distribution of MEA for the new clamping mechanism is more uniform than the conventional one.

Abstract Clamping mechanisms have significant effect on the performance of polymer electrolyte membrane (PEM) fuel cells. In this paper, PEM fuel cell with new clamping mechanism is designed to study the contact pressure distribution over the active area of PEM fuel cell's membrane electrode assembly (MEA). The clamping pressure is pneumatically exerted on the PEM fuel cell assembly. A comparison between the conventional and new clamping mechanism is carried out with simulation, and the numerical results are validated against experimental investigation performed in the fuel cell technology research laboratory. The experimental results are gathered using embedded pressure measurement films in the designed single cell. The results achieved via finite element method are in good agreement with experimental results. It is concluded that the contact pressure distribution of MEA for the new clamping mechanism is more uniform than the conventional one.

Abstract In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.

Abstract In this paper, energy and exergy analyses of the geothermal-based hydrogen production via thermochemical water decomposition using a new, four-step copper–chlorine (Cu–Cl) cycle are conducted, and the respective cycle energy and exergy efficiencies are examined. Also, a parametric study is performed to investigate how each step of the cycle and its overall cycle performance are affected by reference environment temperatures, reaction temperatures, as well as energy efficiency of the geothermal power plant itself. As a result, overall energy and exergy efficiencies of the cycle are found to be 21.67% and 19.35%, respectively, for a reference case.

This study investigates the thermoeconomic performance of a new integrated system including a regenerative two stage organic Rankine cycle which is coupled with a parabolic trough collector via a thermal storage tank. The cold energy of liquefied natural gas (LNG) is used to absorb the heat duty of condenser. The LNG subsystem not only allows the ORC cycle to produce more power by reducing its condensate pressure, but also provides the system with extra power via the LNG expander and chilled water. The system is capable of producing power with solar fraction of a hundred percent during the day. The thermoeconomic analysis is performed to optimize the system for design point conditions. The analysis also reveals the exergoeconomic criteria on system components. Results show that solar collector has the most value of Z˙+C˙D which is due to both high exergy destruction and high investment costs of solar collector. Also, storage tank and condenser are the second and third important components with respect to exergoeconomic criterion. Parametric analysis is performed on the system to show the effects of eleven key thermodynamic parameters on system performance. In order for optimization, the product cost rate and exergy efficiency are chosen as the objectives. Eleven decision variables including inlet temperature and pressure of the turbines, heat exchanger minimum temperature differences along with the mass flow rate of storage tank, condensate pressure and LNG pressure were chosen according to parametric analysis. With the aid of TOPSIS decision making technique, the optimal point was selected among the Pareto frontier of the genetic algorithm. Results show that system can reach the efficiency of 19.59% and product cost rate of 3.88 million dollars per year.

This study investigates the thermoeconomic performance of a new integrated system including a regenerative two stage organic Rankine cycle which is coupled with a parabolic trough collector via a thermal storage tank. The cold energy of liquefied natural gas (LNG) is used to absorb the heat duty of condenser. The LNG subsystem not only allows the ORC cycle to produce more power by reducing its condensate pressure, but also provides the system with extra power via the LNG expander and chilled water. The system is capable of producing power with solar fraction of a hundred percent during the day. The thermoeconomic analysis is performed to optimize the system for design point conditions. The analysis also reveals the exergoeconomic criteria on system components. Results show that solar collector has the most value of Z˙+C˙D which is due to both high exergy destruction and high investment costs of solar collector. Also, storage tank and condenser are the second and third important components with respect to exergoeconomic criterion. Parametric analysis is performed on the system to show the effects of eleven key thermodynamic parameters on system performance. In order for optimization, the product cost rate and exergy efficiency are chosen as the objectives. Eleven decision variables including inlet temperature and pressure of the turbines, heat exchanger minimum temperature differences along with the mass flow rate of storage tank, condensate pressure and LNG pressure were chosen according to parametric analysis. With the aid of TOPSIS decision making technique, the optimal point was selected among the Pareto frontier of the genetic algorithm. Results show that system can reach the efficiency of 19.59% and product cost rate of 3.88 million dollars per year.