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This paper aims to provide comprehensive 4E (energy, exergy, exergoeconomic, and exergoenvironmental) and advanced exergy analyses of the Refrigeration Cycle (RC) and Heat Recovery Refrigeration Cycle (HRRC) and comparison of the performance with R744 (CO2) and R744A (N2O) working fluids. Moreover, multi-objective optimization of the systems has been considered to define the optimal conditions and the best cycle from various perspectives. In HRRC, heat recovery is used as a heat source for an organic Rankine cycle. The energy and exergy analysis results show that utilizing HRRC with both refrigerants increases the coefficient of performance (COP) and exergy efficiency. COP and exergy efficiency for HRRC-R744 have been obtained 2.82 and 30.7%, respectively. Due to the better thermodynamic performance of HRRC, other analyses have been performed on this cycle. Exergoeconomic analysis results show that using R744A leads to an increase in the total product cost. Total product cost with R744 and R744A have been calculated by 1.56 $/h and 1.96$/h, respectively. Additionally, to obtain the processes' environmental impact, Life Cycle Assessment (LCA) is used. Exergoenvironmental analysis showed that using R744A increases the product environmental impact by 32%. Owning to the high amount of endogenous exergy destruction rate in the compressor and ejector compared to other equipment, they have more priority for improvement. Multi-objective optimization has been performed with exergy efficiency and total product cost objective functions as well as COP and product environmental impact for both refrigerants, which indicates that HRRC-R744 has better performance economically and environmentally. In optimal condition, the value of exergy efficiency, total product cost, COP, and the product environmental impact have been accounted for by 28.51%, 1.44 $/h, 2.76, and 149.01 mpts/h, respectively. [ABSTRACT FROM AUTHOR]

In this paper, performance of a steam ejector designed based on the constant rate of momentum change (CRMC) and traditional ejector were tested in an attempt to compare its performance. Three different ejectors were designed and constructed; traditional ejector with throat diameter of 19 mm, traditional ejector with throat diameter of 13.4 mm, and CRMC ejector with throat diameter of 13.4 mm. They were designed to be easily equipped with the 1kW experimental ejector refrigerator. The boiler saturation pressure was varied from 130°C to 140°. The evaporator saturation temperature were fixed at 7.5°C. The result show that at the same operating condition and the same ejector area ratio (the area ratio of nozzle throat to ejector throat), CRMC ejector provided higher entrainment ratio than the traditional ejectors while the critical condenser pressure remain the same. [ABSTRACT FROM AUTHOR]

To explore the influence of heat reservoirs of total thermal capacity at high and low temperature side heat exchanger of an irreversible refrigeration cycle on the coefficient of performance, the cycle model is established. By using the irreversible thermodynamics, much progress had been made in the studies of thermal resistance, heat leak and irreversible factors on the cycle of the coefficient of performance. The analytical formula of coefficient of performance and the distribution ratio of total thermal capacity are derived when the total thermal capacity at high and low temperature side heat exchanger is a constant. The influences of cycle parameters and different kinds of irreversible factors on the coefficient of performance and the optimal distribution ratio are analyzed by numerical computation. The results indicate that the coefficient of performance increases with the increase of the total heat capacity, and decreases with heat leak and internal irreversible factors. Furthermore, the optimal distribution ratio of total thermal capacity, when coefficient of performance reaches the maximum value, only has a connection with the internal dissipation. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a combination between pinch and exergy analysis was applied for refrigeration cycle in NGL recovery plant. Pinch analysis is an established systematic tool for the optimal design and retrofit of energy recovery systems. Unfortunately, one of the main limitations of pinch analysis technique in optimizing energy recovery systems is that it can only deal with heat transfer processes, not processes involving power utilization. Hence, for optimization of shaft work, an exergy-pinch method should be used. A commercial simulator was used to obtain thermodynamic properties of the process streams and to perform mass and energy balances. The equations of exergy destruction and exergetic efficiency for the main system components such as heat exchangers, compressors and throttle valves were developed. First, the refrigeration cycle of the NGL plant was analyzed and optimized by combined exergy-pinch analysis. In doing so, the work of the compressor was reduced to 170 kw. In the last part, the refrigerant was replaced with R-600a which resulted in the reduction of work of compressor and refrigerant mass flow rate by about 570 kw and 11.5%, respectively. [Copyright &y& Elsevier]

The thermodynamic performances for the model established in Part 1 of this paper are optimised by adjusting the mass flowrate. When the optimisation is performed with the constraints of the fixed power input and the plant size, the coefficient of performance can be maximised again by properly allocating the fixed flow area among the compressor inlet and the expander outlet. The coefficient of performance of refrigeration can be maximised again by properly allocating the fixed heat conductance inventory among the hot and cold side exchangers and the regenerator. The obtained maxima reach its maxima at optimal compressor pressure ratio. When the heat conductance distribution of the regenerator is fixed for the heat pump, the coefficient of performance can be maximised again by properly allocating the fixed heat conductance inventory between the hot and cold side exchangers. The obtained maxima reach its maxima at optimal compressor pressure ratio. [ABSTRACT FROM AUTHOR]

A thermodynamic model for an open regenerated inverse Brayton cycle with pressure drop irreversibilities is established using finite time thermodynamics considering the size constraints of real plant in Part 1 of this paper. The analytical formulae about the cooling load and coefficient of performance of refrigeration cycle, the heating load and coefficient of performance of heat pump cycle are derived, which indicate that the thermodynamic performance for open regenerated inverse Brayton cycle can be optimised by adjusting the mass flowrate. It is shown that the cooling load, heating load and the power input increase with the increase in the compressor inlet relative pressure drops, the coefficient of performance reaches its maximum at the optimal compressor ratio and the exhaust temperature is higher than that of the ambient, which is lower than that of the ambient only at small effectiveness of the regenerator. [ABSTRACT FROM AUTHOR]

To teach and explain system modelling in a Thermal-Fluid application is a challenge: learning how one component or even the surrounding conditions can influence the performance of the rest of the components of the system and the system itself is not an easy task. However a suitable, educational implementation may help students gain a deeper understanding not only of the system itself but of the existing interrelation between the Thermal-Fluid fields: Thermodynamics. Heat Transfer and Fluid Mechanics. In this study a refrigerating cycle simulator is used. The simulator is prepared in such a way that the interrelation between each component, the system and the surroundings can be analysed by the students. This case study is found to be very useful due of its ability to study system performance. A three-step educational implementation, the simulator being the third step, has been used and found to be enriching both for students and instructors. [ABSTRACT FROM AUTHOR]