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Due to the lack of natural water resources and high consumption of water in industries, desalination systems are good options to supply water demands, especially in regions with a water crisis. If these wastes are used in thermal desalination cycles, in addition to improving efficiency and reducing energy consumption, the production of environmental pollutants can also be reduced. In this paper, the multi-stage flash brine recirculation (MSF-BR) system of the Abadan refinery is investigated from energy-exergy-exergoeconomic viewpoints. In addition, the effects of top brine temperature (TBT), number of stages and ambient temperature on the performance of the system are evaluated. The results at maximum brine temperature show that with increasing the TBT, the exergy efficiency, gained output ratio (GOR) and distillate water production increase by 34%, 47% and 47%, respectively. It is also found that if the number of stages in the heat rejection section increases to more than six stages, GOR will decrease. The exergoeconomic analysis results reveal that the relative cost difference increases by 94% with an increase in the number of stages. Finally, it is concluded that by using the waste heat of a refinery complex for heating steam to run the desalination system, there is a 9103$/year cost savings due to energy consumption reduction and 193 × 104 $ /year cost savings due to CO2 emission reduction.

Diverse methods have been proposed for liquefying gases due to their need in different industries. This study examined the precooled Linde–Hampson cycle for liquefying six gases. First, the proposed system is analyzed from a thermodynamic perspective. Then, the effects of pressure ratio on performance parameters such as system required work, heat exchanger-specific heat capacity, number of transfer units, the liquefied gas mass ratio, Coefficient of Performance (COP), and exergy efficiency are examined. The results show that methane at a pressure ratio of 40 has the highest COP (1.606), while argon at a pressure ratio of 220 has the highest exergy efficiency (31.51%). Exergy analysis indicates that the Joule–Thomson valve destroys the most exergy, followed by heat exchanger-3 and compressor-1. Finally, the TOPSIS technique is used as a multi-objective optimization method to optimize the compressor-1 pressure ratio based on two objective functions, COP and exergy efficiency. The results show that in optimal conditions, COP and exergy efficiency are respectively 0.99 and 20.6% for air, 0.93 and 28.35% for argon, 0.97 and 20% for nitrogen, 1.46 and 14.76% for methane, 1.05 and 22.87% for fluorine, and 1.18 and 20.08% for oxygen.

The present research has analyzed the energy and exergy of a combined system of simultaneous power generation and cooling. To provide a comprehensive data sheet of this system, the system has been investigated in the temperature range of 300–800 °C, and 6 working fluids, including air, carbon dioxide, nitrogen, argon, xenon, and helium, have been investigated. The parameters affecting the performance of the system, namely the compressor inlet pressure, the compressor pressure ratio, and the intermediation pressure ratio were investigated. The power produced by the Brayton cycle at a pressure ratio of 5.2 is the highest due to the increase in compressor power consumption and turbine power generation. The results of the parametric study showed that the exergy efficiency of the system has the maximum value at the pressure ratio of 4.73. The results of the parametric study showed that increasing the pressure of the compressor does not have a significant effect on the electricity consumption and the temperature of the working fluid due to the constant pressure ratio. The input energy to the heat exchanger of the absorption chiller decreases with the increase in the Brayton cycle pressure ratio, and as a result, the cooling created by the chiller also decreases. In this method, three objective functions of exergy efficiency, energy efficiency, and total production power are considered as objective functions. The most optimal value of intermediation pressure ratio was obtained after the optimization process of 1.389. Also, the most optimal value of the pressure ratio of high-pressure and low-pressure turbines was reported as 2.563 and 1.845, respectively.

One of the most important approaches for energy consumption reduction in buildings is employing thermal insulation. Phase change materials (PCM) can be used in many insulation applications due to their high heat capacity, low heat transfer coefficient and energy storage potential. In this study, the numerical simulation is used to investigate the effect of employing PCM as thermal insulation in the educational building of Hakim Sabzevari University located in Iran during the six hot months of the year. For this purpose, the optimal location of PCM layer into the wall is firstly determined, and then, different PCM thicknesses of 2, 3, 4 and 5 cm are examined. It is found that the ratio of heat exchange reduction using PCM layer with thicknesses of 2, 3, 4 and 5 cm is equal to 9.8%, 13.4%, 17.5% and 20.4%, respectively. Finally, the amount of energy saving and payback period for different thicknesses of PCM are calculated based on thermo-economic analysis. Accordingly, an optimal PCM thickness of 3 cm is obtained using Pareto solutions and TOPSIS method which leads to a payback period of 50 months.