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Component of vapor-compression refrigeration cycle was modeled at steady state condition. Then, modeling and simulation of the whole cycle was performed to predict system parameters such as compressor work, cooling effect and coefficient of performance (COP) in various ambient conditions. The simulation results were compared with experimental results obtained from an experimental investigation on a split-type air conditioner. It was found that the experimental and simulation results are in good agreement and the model can predict the performance of the cycle successfully. Average difference between experimental and simulation results for prediction of COP was 4.5%. Simulation results show that for each 1℃ increase in ambient temperature, COP reduces 3.5%, and for 10% increase in ambient relative humidity, COP increases about 6.5%. Also, by increasing the air volumetric flow rate of condenser about 10%, COP increases about 5%. Effect of increasing the condenser area on its heat rejection rate was studied and it was found that increasing the condenser area, increases the heat rejection rate substantially only in a limited range and after that it does not change.

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This article presents a transient model of a solar adsorption cooling system. A computer program is developed to simulate the operation of a two-bed silica gel- water adsorption cooling system as well as flat plate collectors and the hot water storage tank. This program is then utilized to simulate the performance of a sample solar adsorption cooling system used for cooling a set of rooms that comprises an area of 52 m2 located in Ahwaz city in Iran. The results include the temperature profiles of hot, cooling and chilled water in addition to adsorption/desorption beds, evaporator and condenser, collector hot water temperature, auxiliary heater fuel consumption and solar fraction of the system. Furthermore, the effect of the cycle time on COP (coefficient of performance), SCP (Specific Cooling Power), refrigeration capacity, fuel consumption and solar fraction is studied. The results show that the cycle time increases COP and SF of the cycle but decreases cooling capacity and supplementary heater fuel consumption.

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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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Throttling process through expansion valves causes a considerable amount of exergy loss so that reducing this loss improves the performance of compressed refrigeration cycle considerably. In the present work, the effect of using an ejector on the performance of a cascade refrigeration cycle is evaluated. It is concluded that the using ejector and selecting R134a as the high temperature circuit refrigerant cause the COP and second law efficiency to increase by approximately 6.5 percent as compared to the conventional cascade cycle with the same cooling capacity. In addition, several refrigerants including R717, R290, R134a, and R123 are examined to reveal the effect of refrigerant type in the high temperature circuit on the cycle performance. It is also found that, at a temperature of more than 255.4 K, for the evaporator of high temperature circuit, the refrigerant combination of R744-R123 results in a better performance as compared to the other combinations. Finally, the cycle performance is optimized with respect to the temperatures of low temperature evaporator, high temperature evaporator, and the ambient from the view points of both the first and second laws of thermodynamics. It is concluded that the COP and the second law efficiency are the highest when R123 is used as the refrigerant at the high temperature circuit.

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In critical situations such as floods and earthquakes, the relief forces require a refrigerator for pharmaceuticals and vaccines which can operate without electrical energy and instead, it uses alternative energies such as solar energy, vehicle exhaust energy, wind energy, etc. In this paper, modeling of a refrigerator with an adsorption refrigeration cycle using activated carbon/methanol as adsorbent/adsorbate pair which utilizes two sources of energy, solar energy and vehicle exhaust energy is presented in MATLAB. The solar refrigeration cycle includes a collector with area of 1m2 and the exhaust gas cycle includes a heat exchanger with temperature difference of 100°C between its inlet and outlet gases. Modeling results represent the temperature profile in adsorbent bed, evaporator and condenser. Moreover, the pressure profile, overall heat transfer coefficient of collector and adsorbent bed, concentration and solar radiation are reported. The results show coefficient of performance of 0.5491 and solar coefficient of performance of 0.2000 for solar adsorption refrigeration and coefficient of performance of 0.5607 with specific cooling power of 2.4777 for exhaust heat adsorption refrigeration. These results reveal the good performance of the proposed model in the climate of Iran.

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In the recent decades, due to environmental sustainability, abundance, availability and appropriate thermo-physical properties, natural refrigerants are being considered with potential of substitute refrigerants. In this study, Propylene (R1270), Propane (R290), Isobutane (R600a), R407c, R410a, R12, R22 and R134a have been investigated as refrigerant in common refrigeration systems. In the case studies, the thermodynamic and technical parameters of the cycle, using above mentioned refrigerants, have been investigated for common refrigeration systems in temperature range of -30°C to 10°C in the evaporator, and also for heat pump systems with a temperature range of 45°C to 60°C in the condenser. Finally, Propylene was introduced as a refrigerant to replace with synthetic refrigerants in the above mentioned temperature ranges in common refrigeration cycles.

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Supercritical carbon dioxide refrigeration is a proposed system to provide extremely low temperatures. The waste heat from the gas-cooler is noticeable. So, it can be used as a promising heat source in other systems like multi-effect-desalination system (MED), in order to provide cooling and fresh water, simultaneously; as well as reduction of power consumption. In this paper, the energy analysis and comparison of two novel combined systems are carried out. The combined systems consist of CO2 refrigeration system and two MED's models, the Boosted model and the water preheaters (PH) model. The effect of operating parameters such as evaporator temperature, ambient temperature and compressor outlet pressure on system performances are studied. Results showed that for both combined systems, by decreasing the evaporator temperature or increasing the ambient temperature, the coefficient of performance (COP) and the distilled water flow rate, decreases and increases, respectively. On the other hand, increasing the compressor outlet pressure would increase COP and decrease distilled water flow rate up to an optimum point. Also, MED-Boosted could produce more fresh water compared to MED-PH. In order to decrease the power consumption of the combined system two methods are presented. In two compressors method the COP enhances 6.2% compared to the base system (consists of one compressor and an expansion valve). However, the produced fresh water would be reduced by 60%. On the other hand, the expander method could improve the COP by 23.4%, compared to the base system, while the amount of distillated water decreases less than 8%.

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The existence of huge gas resource in Iran and the global demand for the replacement of fossil fuels with this cleaner energy resource has caused that the large-scale gas export becomes an interesting topic. One of the methods for large-scale gas exports is liquefaction which is done by refrigeration cycle. Considering the importance of the efficient use and the reduction in energy consumption, particularly in large energy consumers like liquefaction plants, it is imperative to optimize the refrigeration cycles used in these plants. While there have been many studies focusing on the power consumption minimization of refrigeration cycles, however, in most of these studies the performance limitations of the refrigeration cycle components have not been considered. Therefore, the results of such studies are not practical for in-use refrigeration cycles in gas refineries. The main goal of this paper is to propose a systematic method to minimize the power consumption of in-use refrigeration cycles in gas liquefaction processes by taking into account the performance limitations of refrigeration cycle components and the interactions between the refrigeration cycle and the core process. In this regard, a combination of thermodynamic viewpoints and pinch technology is used as well as considering the above mentioned limitations, to express the multi-stage refrigeration cycles’ power consumption minimization problem as a function of several independent variables. Up to 15% reduction in the specific power consumption is achieved when the proposed method are implemented on the optimization of a typical in-use three-stage refrigeration cycle, used in a propane liquefaction plant.

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In this paper, using a hybrid compression-absorption refrigeration system for providing cooling demand of air condition and fridges for meat, fish vegetable and dairy preservation, simultaneously on a ship is proposed. Cooling demands for air condition and fridges are in each ship. So, the use of proposed system can be considered in all ships and is not limited to a special one. Exhaust gases of auxiliary engine are applied as a heat source for absorption section. The results show that exhaust gases heat recovered is higher than the demand of generator on all ranges of engine loads. Unlike main engine, auxiliary engines are always on and don’t depend on the movement of ship. So, exhaust gases of auxiliary engine as a heat source is an appropriate and permanent heat source for generator of absorption section. Based on energy, exergy and environmental analysis, a comparative performance analysis of proposed system and conventional system (vapor compression refrigeration system) has been carried out. The results show that based on tropical condition, fuel consumption and total irreversibility of proposed system are respectively 91.6% and 26.6% less than conventional system. Using a hybrid compression-absoption refrigeration system in comparison to vapor compression refrigeration system causes 64834 $ annual saving due to reduction in CO2 emission penalty(cost).

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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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Effects of combined use of black barberry (Berberis crataegina L.) extract and sodium nitrite on the quality and shelf life of cooked beef sausages were investigated. Different concentrations of the extract (30, 60 and 90 mg kg^-1) in combination with nitrite (30, 60 and 90 mg kg^-1) were added to sausage formulations.. Total viable counts, pH, proximate analysis, residual nitrite level, lipid oxidation, color and sensory data were studied against the blank and control samples during the storage for 30 days at 4°C. A gradual decrease in the nitrite level was observed during the storage for all samples studied. Samples using the extract from this study showed similar redness but lower lightness when compared to the control sausage sample with 120 mg kg^-1 sodium nitrite. Sensory evaluation of the samples indicated similar results to those of the control. Accordingly, there is a potential benefit for partial replacement of sodium nitrite with barberry extract in the cured meat products.

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In this study, the thermoeconomic performance of absorption refrigeration cycle utilizing binary solution containing water - ionic liquid (1-Ethyl-3-Methylimidazolium Trifluoroacetate) is investigated and compared with the water-lithium bromide cycle. For this purpose, the thermodynamic and thermoeconomic analysis have been employed to simulation of the cycle and then, the effects of design parameters on the performance parameters like coefficient of performance, exergetic efficiency, solution circulation flow ratio, area of heat exchangers and cost of the streams are studied. The thermodynamic properties of the binary solution are predicted using Non-Random Two Liquids model. It has been found the system with ionic liquid has a lower coefficient of performance and exergetic efficiency (0.66, 10.15%) than aqueous solution of lithium bromide system (0.78, 12 %). The total area and total cost of the ionic liquid system (49 m2, 4907 $/year) is larger than water-lithium bromide cycle (16 m2, 3347 $/year). Despite the Lower performance of systems with ionic liquid, the advantages of these liquids like no crystallization, negligible vapor pressure and weak corrosion tendency to iron-steel materials make the new working pair suited for the absorption refrigeration cycle.

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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.

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In this paper, the combined carbon dioxide power and ejector compression refrigeration cogeneration cycle with the ability to change the production capacity of power and cooling ​​by changing the performance parameters of the cogeneration cycle has been analyzed. Thermodynamic simulation of the studied cogeneration cycle has performed in EES software and the energy and exergy balance equations for each component of the cycle are applied. Then, a parametric study has been carried out and the variations of the performance parameters of the cogeneration cycle, including the turbine inlet temperature and pressure, the outlet pressure of the power cycle, the evaporator temperature, etc. are investigated on the overall thermodynamic performance of the cogeneration cycle. The results indicate that the exergy efficiency of the studied cogeneration cycle reaches to the optimum value of 28.8% at the turbine inlet pressure of 21100 kPa, while the maximum value of the total produced power and cooling of the studied cycle occurs at the turbine inlet pressure of 18600 kPa. Also the contribution of different components of the studied cogeneration cycle in the total exergy destruction rate is calculated and it is revealed that the turbine and the heater have the highest exergy destruction rate values, respectively, among the components of the cogeneration system