This case study analyzes a cryogenic air separation unit (ASU) with a production of V˙O2=58300 [m3Nh] of gaseous oxygen with a concentration greater than 98.5%, operating in Romania on a steel plant platform. The goal of the paper is to provide an extensive model of exergetic analysis that could be used in an optimization procedure when decisional parameters are changed or structural design modifications are implemented. For each key part of the Air Separation Unit, an exergetic product and fuel were defined and, based on their definition, the coefficient of performance of each functional zone was calculated. The information about the magnitude of the exergetic losses offers solutions for their future recovery. The analysis of the exergy destructions suggests when it is worth making a larger investment. The exergetic analysis of the compression area of the ASU points out an exergy destruction and loss of 37% from the total plant’s electrical energy input. The exergy loss with the heat transferred to the cooling system of compressors can be recovered; for the exergy destruction portion, the challenge between investment and operating costs should be considered. The exergy destruction of the air separation columns found the High Pressure Column (HPC) to be more destructive than the Low Pressure Column. The share of the exergy destruction in the total plant’s electrical energy input is 8.3% for the HPC. The local COP of the HPC, calculated depending on the total exergy of the local product and fuel, is 62.66%. The calculus of the air separation column is performed with the ChemSep simulator.
In the present paper, performance and exergy analysis for a vapor compression refrigeration system (VCRS) operating with eco-friendly refrigerants such as R1234ze and R1234fyare tested under different operation conditions to change the recently worked refrigerants R-134a. An analysis through performance and exergy is performed to guide the thermodynamic improvement for the VCRS. Additionally, a comprehensive study is conducted to examine the effects of subcooling temperature on performance and exergy destruction in all components of the VCRS. The exergy destruction of the compressors, condenser, evaporator and expansion device were calculated to obtain the exergy efficiencies. For simulation and analysis the VCRS, Engineering Equation Solver (EES) software program was utilized to obtain the thermodynamics refrigerant properties in which the system operates with the highest eco-friendly, energy and exergy performance is developed the VCRS to determine the most suitable alternative refrigerant to replace the R134a. The results indicate that the refrigerant R1234yf showed the greatest COP enhancement 16.7% due to subcooling, followed by R1234ze 14% and R134a 12.8% under the same operating conditions.
In the paper, a thermodynamic analysis of an air conditioning system necessary to store a quantity of 500 kg of apricots at a temperature of 10°C and a humidity of 90% in a fruit warehouse was aimed at. The storage
facility is cooled by means of an air handling unit (AHU). The energetic and exergetic analysis was carried out on the air conditioning system that treats a mixture of fresh air and recirculated air for various fractions of fresh air ranging from 0 to 100%, thus being able to perform a finer analysis of the operation of the installation under different working conditions. Based on the exergy analysis, the exergy loss was estimated for each device, depending on their destination and operating mode. Numerical and graphical results are presented related to the necessary mass flow rates of the air, the refrigeration load, the necessary treatment and evolution of humid air in the system, as well as the exergy loss in the main components of the air conditioning system. This theoretical study was carried out to obtain quantitative information that will lead to a better understanding of the air conditioning irreversibility process and their distribution amongst the system component and minimizing them for optimal air conditioning cycle.
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