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The aim of this article is to compare a direct hybrid system of gas turbine and solid oxide fuel cell with an indirect system from thermodynamic and exergy viewpoints. According to importance of fuel cell role in hybrid cycles and providing further proportion of produced power, discrete and complete thermodynamic, electrochemical and thermal analyses have been done. Calculation of working temperature which has an impact on system performance is one of the most significant works that is done in this article. In addition, by parametric study of this hybrid system, the influence of inlet air rate and compression ratio on efficiency, power and exergy destruction rate has been perused and eventually an optimized state for system will be offered. Results indicate that a direct hybrid system is more efficient in comparison with an indirect system. Higher efficiency, less irreversibility, higher power, and less pollution are the most important advantages of direct hybrid systems.

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In this paper the performance of an ejector refrigeration cycle was investigated theoretically and experimentally. Making use of the conservation of mass and energy as well as the exergy balance equations, a two-dimensional thermodynamic model was developed. The influence of flow viscosity is taken into account through considering a two-dimensional flow near the ejector inner wall. The results indicate a decrease of COP with increasing generator temperature and an increase of second law efficiency with increasing evaporator temperature and/or decreasing generator temperature. It is found that at any generator temperature, there exist a particular evaporator temperature above which the exergy destruction in the condenser is higher than that in the ejector. The maximum relative and the root mean square errors in calculating the entrainment ratio at three generator temperatures of 77, 83 90 o C are obtained as 7.76% and 5.13% respectively. Also the exergy destruction in the evaporator at an evaporator temperature of 13.5 oC, was found to be the highest among those occur in the other components of the cycle.

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A tri-generation cycle consisting of a homogeneous charge compression ignition (HCCI) engine and an ammonia-water absorption cogeneration cycle are proposed and analyzed. The energy of engine exhaust gases are utilized to run absorption cogeneration cycle. Also the energy of cooling water can be used in residential applications. A single zone model with capability to consider chemical kinetic talculations is developed for the HCCI engine. The results show that increasing the pump pressure ratio of the cogeneration cycle causes a decrease in the refrigeration output and an increase in first law efficiency. At a particular value of this pressure ratio the second law efficiency is maximized. It is shown that the contribution of engine in the total exergy destruction in the tri-generation system is much higher than those of the other components. With an ammonia concentration of 0.4 in the solution leaving the absorber and with an ambient temperature of 25oC, the maximum exergy efficiency occurs when the pump pressure ratio is 9.486. At this condition, the fuel energy saving ratio and CO2 emission reduction are 27.97% and 4.8%, respectively. It is also shown that the second law efficiency of the tri-generation system is 5.4% higher than the second law efficiency of the HCCI engine.

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In this article, a combined GAX-ejector absorption refrigeration cycle is proposed and its performance is compared with those of combined single effect-ejector, simple GAX and single effect absorption refrigeration cycles. For the ejector, based on the Keenan's theory, a new model is developed and validated and then is combined with the developed models in the EES software (for simulating the processes in the cycles). After obtaining the optimum critical area ratio for the ejector, three different ejectors, with the mentioned specification, are selected for the combined GAX-ejector and combined single effect-ejector cycles. The performance of these cycles is investigated through changing their evaporator and generator temperatures. Results indicate that, at identical conditions, the COP and second law efficiency of the combined GAX-ejector cycle are around 25% and 16% higher than those of the combined single effect-ejector absorption refrigeration cycle. In addition, it is observed that as the generator temperature increases from 140 oC to170oC, the COP and second law efficiency of combined GAX-ejector cycle are maximized at a particular generator temperature. However, at similar condition, an increase in generator temperature results in a decrease of the COP and second law efficiency of combined single effect-ejector refrigeration cycle.

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As the coefficient of performance and the cooling power of adsorption chillers are low, the irreversibility calculation can identify the sources which limit the increase of performance parameters and effectively be used in association with current performance improvement techniques. Adopting the numerical modeling and calculating the temporal distribution of temperature in adsorber elements, this study measures the exergy destruction in different parts and processes of the adsorbent bed. The results show the maximum exergy destruction rate in isosteric phases, yet the total exergy destruction is low due to the short phase times. The highest total exergy loss is observed in isobaric heating phase due to the high irreversibility of desorption process and also long phase duration. Furthermore the effects of fin height and fin spacing on the exergy destruction of adsorbent bed are investigated. The results show that increasing fin height and fin spacing increase the total exergy destruction; however the dependency of fin spacing on exergy destruction is relatively low.

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In this paper in order to study of effective parameters on energy and exergy efficiency, the modeling and analysis of fluidized bed dryer of Bandar Imam Petrochemical Complex is performed. For do this paper the commercial code with Euler-Euler two phase flow modeling has been used. Due to the importance of moisture content in the dryer system and method transfer between solid and gas phases, a numerical algorithm for estimating moisture content in each phase and exchange or transfer between phases in the proposed the mentioned, implement the code. With applying this algorithm in the code led to considerable correspondence between the results of modeling and the results from the actual performance of the dryer. The difference between the modeling and the experimental results is maximum 1% that represents significant fitness with similar works. The results also express that increase in inlet air and heat exchanger hot water mass flow rates, reduce efficiency while increment in the mass flow rate and temperature of products increase the efficiency. The results of this research for the mentioned petrochemical complex show that with the 15 % increase in mass flow rate of inlet product, overall efficiency of the dryer rises from 38.62 % to %42 and exergy efficiency increases from 35.16 % to 39.5 % while the product moisture decreases 18%.

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Low swirl burners present an effective approach to increase stability in lean premixed combustion. Effects of swirl number as a key parameter in the performance of these burners have been investigated in several studies with different conditions of pressure, bulk velocity equivalence ratio and geometrical specifications. Swirler distance from the exit, called recess length is another key parameter, which affects the performance of the burner and there are a few studies about its effects on the performance of the burner. In this study by design and fabrication of a low swirl burner and setup a rig test, several combustion parameters include flame temperature; flow rate, pressure and temperature of the air and fuel, and analysis of combustion products have been measured. And the effects of recess length and equivalence ratio variations on the performance of the low swirl burner have been studied. In addition, the exergy analysis has been done in order to investigate the performance of these burners. Results reveal that increasing recess length would result in wider range of lifted flame for different equivalence ratios. In addition, results also show that although low swirl combustion is working on lean condition, it has about 17 percent lower irreversibility ratio in comparison with diffusion flame from second law of thermodynamic point of view. Besides, the heat transfer ratio has been increased about 14 percent in the lifted flame in comparison with the attached flame.

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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.

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In order to power and hydrogen production, combination of Matiant cycle with an ORC cycle and PEM electrolysis have been analyzed from the viewpoint of energy and exergy. Waste heat of the Matiant cycle is used to run the ORC cycle. Effect of some decision variables i.e. evaporator temperature, minimum temperature difference in heat exchanger, degree of superheating in ORC turbine inlet and isentropic efficiency of ORC turbine on the rate of produced hydrogen, ORC produced power and exergy efficiency of the combined system have investigated. It is observed that, increasing minimum temperature difference leads to decrease in the rate of produced hydrogen, ORC produced power and consequently exergy efficiency of the combined system. Also change in the evaporator temperature makes an optimum value of rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system. It is obtained that, rising the degree of superheating in the ORC turbine inlet decreases the rate of produced hydrogen, ORC produced power and the exergy efficiency of the combined system. As it was expected, increasing isentropic efficiency of ORC turbine leads to an increase in rate of produced hydrogen, ORC produced power and therefore the exergy efficiency of the combined system.

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In the current study a combined heat and power (CHP) system based on diesel engines is studied. A CHP system is investigated parametrically according to first and second laws of thermodynamics. In this investigation instead of modeling the air standard cycle, the fuel air standard cycle and fuel combustion are simulated, which leads to more accurate results. Since a standard cycle has many differences with an actual cycle, the exhaust gas from combustion chamber of a diesel engine is also used to simulate the CHP system, and the heat exchanger of the CHP is investigated from exergetic and economic viewpoints. It was seen that applying the pre-described system, it is possible to warm up 0.17Kg/s water from 25°C to 68.64°C. This enhances the overall efficiency of the system about 20%, raising it up to 80%. Exergy destruction in heat exchanger is almost high which is due to heat transfer process and high temperature difference in the heat exchanger.

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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.

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In this study, energy and exergy analysis of a two bed adsorption cooling system have been performed. Silica gel-water has been chosen as the adsorbent-refrigerant pair. Analysis is performed for evaluating the effect of operating conditions on the optimal timing and then on the maximum value of the SCP, COP, effectiveness and the minimum value of internal irreversibility and external irreversibility. A lumped parameter mathematical model and a global optimization method called the particle swarm optimization have been used to reach this purpose. In this model, internal and external irreversibility have been calculated with the new method without calculating irreversibility of the cycle internal component. Energy analysis showed that maximum of SCP increases with the increase of the mass flow rate and heat source temperature. Furthermore, an increase in the heat source temperature causes an increase in the COP, but an increase of the mass flow rate causes a decrease in the COP. Exergy analysis reviled that depending on the mass flow rate and heat source temperature, 65-90% of input exergy was expended by internal irreversibility, 1–20% were expended by external irreversibility and 8-14% is transferred to the cold reservoir in evaporator. It is concluded at the low-temperature heat source if the mass flow rate is chosen less than 0.6 kg/effectiveness at heat source temperature 75 is more than 65 and vice versa.

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Considering the daily increase of consumption and expense of nonrenewable energies such as natural gas and electricity, application of clean and renewable energies such as solar thermal energy nowadays has been highly taken into consideration. In this research, at first, simple steam Rankine cycle and two different configurations of combined steam and organic Rankine cycles with parabolic trough solar collector as heat source are simulated from energetic and exergetic point of view. First configuration was basic steam rankine cycle with parabolic trough solar collector (PTSC) as heat source, and other configurations of the combined cycle worked as follows: In the second configuration (combined cycle with intermediate heat exchanger), with the increase of steam condenser pressure, heat dissipation in condenser is used as heat source for bottoming organic Rankine cycle and in the third configuration (combined cycle without intermediate heat exchanger), reduced-temperature solar fluid moving output of steam rankine cycle acted as the organic Rankine cycle heat source. Simulation results in the basic input state show that third configuration has the maximum amount of work and irreversibility and second configuration has the minimum amount of work and irreversibility which in this case, increase in the steam cycle condenser pressure leads to the reduction of work of combined cycle with intermediate heat exchanger, even lower than the simple steam cycle. On the other hand, second configuration has the maximum solar energy and exergy efficiency among three configurations which is due to the reduction of collector area required in this configuration.

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Replacement of expansion valves which are used in natural gas pressure reduction stations, with expansion engine, to recycle wasted energy to generate electricity is the main objective of this study. In these engines, ports are used for inlet and outlet the gas. Control valve geometry set on these ports has a great impact on performance of this engine. In this research, simulation and optimization of the optimum opening and closing time of these valves according to two types of valve, piston and spool valves, to maximize the Exergy Efficiency has been done for the first time which Genetic Algorithm is used for this optimization. Simulation has been conducted with regard to the composition of gas stations which to calculate the thermodynamic properties of natural gas, AGA8 standard is used. For optimization constrain of having no back flow has been applied. Results showed that exergy destruction due to outlet processing in piston valve and due to inlet processing in cylinder valve is more than other destruction sources. Overall engine with cylinder valve has better performance than engine with piston valve. Variation of supply line pressure showed that engine with cylinder valve could not be used in inlet pressure of 30 bar, because engine doesn’t produce power.

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Regarding the growing cost of energy, shortage of resources, and environmental issues, the importance of reducing energy consumption and optimization of related industries has been revealed more than anytime. Solar energy is one of the suitable solutions to acquire clean and cheap energy. The first step is to design the cycle using Aspen HYSYS simulator. After that exergy analysis is carried out on the proposed system. Results show that LPT2, LPT3 and HEX2 have the highest exergy destruction and should be considered for revision. Results of exergy analysis are then examined more deeply with the help of advanced exergy analysis. In this section exergy destruction is divided into four parts, endogenous/exogenous and avoidable/unavoidable to investigate the precise reason of the components’ exergy destruction. Results show that the three components which had the most exergy destruction, are the real reason behind exogenous exergy destruction of the system so by optimizing these components we can also decrease the total exergy destruction of the system too. At last by choosing the right variables and total produced work as the primary function, the optimization is done using the Aspen HYSYS optimizer and the optimized parameters are compared to the basic parameters which resulted in more power production and less exergy destruction and production cost.

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In this study, the performance of a photovoltaic thermal system (PVT) is investigated in a numerical and experimental study. In the numerical part, the Taguchi method is applied to determine the optimum place and time of the PVT system. Moreover, the optimum parameters that are independent of the design of the PVT system are obtained to improve the performance of the system in a specific place and time. Using the specified optimum parameters, the performance of the system is investigated from the energy and exergy viewpoints, experimentally. In the experimental study, using the designed setup, the performance of a water based PVT system is compared with that of a conventional photovoltaic unit (PV). The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The numerical results indicate that the most effective parameter on the performance of the PVT system is the coolant inlet temperature and its optimal value is 20 °C. Moreover, the total energy efficiency of the PVT system in the optimum working condition is 69.02 %. The experimental results reveal that the average output electrical energy of the PVT system is 6.27 % more than that of the PV unit. In addition, the average thermal energy and exergy efficiencies of the PVT system are 34.12 % and 0.72 %, respectively.

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In this study, the effects of using pure water, water/ethylene glycol mixture with 50:50 wt% and pure ethylene glycol as the working fluids on the energy and exergy efficiencies of a photovoltaic thermal (PVT) system are experimentally investigated. Moreover, the performance of the PVT systems are compared with a conventional photovoltaic (PV) system. The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The investigated parameters in this study are: the photovoltaic cells temperature; output electrical and thermal powers; electrical and thermal energy efficiencies; output electrical and thermal exergies; and electrical and thermal exergy efficiencies. Based on the results, the PVT system with water/ethylene glycol mixture increases the output electrical power by about 5.41 % compared to that of the PV system. Furthermore, the results indicate that using pure water in the PVT system enhances electrical and thermal energy efficiencies compared to those of pure ethylene glycol and water/ethylene glycol mixture, whereas the overall exergy efficiency of PVT systems with pure water and water/ethylene glycol mixture working fluids are approximately same.

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In the present research, microwave drying process of potato slices were thermodynamically analyzed and evaluated. During the experiments, potato slices with thicknesses of 3.5, 5, 7 and 9 mm were dried using powers of 200, 400, 600 and 800 W. Specific energy consumption was obtained to be the range of 0.83‒3.29 MJ kg^-1, and significantly increased (p < 0.05) with increasing samples thickness. Energy efficiency of the process (13.23‒35.59) was significantly (p < 0.05) improved with increasing microwave power and decreasing samples thickness. Average specific energy loss of the process varied from 0.69 to 2.71 MJ kg^-1. Exergy efficiency and sustainability index of the process changed from 10.03 to 28.17 % and from 1.11 to 1.39, respectively. In General, according to the results obtained in this research, practicing higher microwave powers to dry thinner samples improved the thermodynamical performance and reduced the environmental footprints of the process.

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An ejector-expansion refrigeration cycle employing N2O is studied in this paper and thermodynamic and exergy analysis is carried out to find out the effect of some key factor within the system. The results show that Ejector-Expansion Refrigeration Cycle (EERC) obviously has the highest maximum coefficient of performance and exergy efficiency by about 12% and 14% more than Internal Heat Exchanger Cycle (IHEC); meanwhile these are about 15% and 16.5% higher than Vapor-Compression Refrigeration Cycle (VCRC) ones, respectively. Moreover, the total exergy destruction in N2O ejector-expansion cycle is 63.3% and 54% less than IHEC and VCRC and the exergy destructed in expansion process within EERC is 19.39% and 40.497% of total destruction less than IHEC and VCRC. Furthermore, the highest COP for vapor-compression refrigeration, internal heat exchanger and ejector-expansion refrigeration cycles is corresponding to the high side pressure of 7.328 Mpa, while this value for CO2 refrigeration cycle is about 8.5 Mpa.

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In this paper, performance analysis and optimization of a trigeneration system based on different thermodynamic criteria such as energy and exergy efficiency, power and dimensionless power have been investigated. The trigeneration system consists of three subsystems which including the solar subsystem, Kalina subsystem and lithium bromide-water absorption chiller subsystem. The proposed system uses solar energy generates power, cooling and domestic water heating. Power is introduced as a tool for understanding thermodynamic concepts of limited time. Dimensionless power is defined as the ratio of power to the product of total thermal conductivity and minimum temperature of the system. Dimensionless power can be used as a tool to understand the concepts of finite time thermodynamics. The exergy analysis has shown that the most exergy destruction is related to boiler. As a result, energy and exergy efficiencies, capital cost rates and dimensionless power are 17.77%, 18.82% and 9.63 dollars per hour, 0.01781 respectively. Sensitivity analysis has shown that increasing parameters such as ambient temperature, solar radiation, the dimensionless mass flow rate of the Kalina cycle, collector inlet temperature and pressure ratio of the Kalina cycle increase energy and exergy efficiencies. Also increasing pressure ratio the of Kalina Cycle, reducing the dimensionless mass flow rate of the Kalina cycle, the ambient temperature and collector inlet temperature has led to increased dimensional power. In addition, the optimization criteria such as energy efficiency, exergy efficiency, power and dimensional power have been compared. The results showed that power and dimensional power are the best thermodynamic optimization criteria.