Abstract
Screening for alternative refrigerants with high energy efficiency and low environmental impacts is one of the highest challenges of the refrigeration sector. This paper investigates the performance and refrigerant screening for single and two stages vapor compression refrigeration cycles. Several pure hydrocarbons, hydrofluorocarbons, hydrofluoroolefins, fluorinated ethers, and binary azeotropic mixtures are proposed as alternative refrigerants to substitute R22 and R134a due to their environmental impacts. The BACKONE equation of state is used to compute the thermodynamic properties of the candidates. The results show that the maximum coefficients of performance (COP) for single and two stage cycles using pure substances are achieved using cyclopentane with values of 4.14 and 4.35, respectively. On the other side, the maximum COP for the two cycles using azeotropic mixtures is accomplished using R134a + RE170 with values of 3.96 and 4.27, respectively. The two-stage cycle presents gain in COP between 5.1% and 19.6% compared with the single-stage cycle based on the used refrigerant. From the obtained results, among all investigated refrigerants, cyclopentane is the most suitable refrigerant for the two cycles from the viewpoint of energy efficiency. However, extra cautions should be taken due to its flammability.
Highlights
Refrigeration systems are widely used in domestic and commercial applications.Approximately, there are three billion refrigeration systems used in the world which represent about17% of the electrical power consumption over worldwide [1]
The BACKONE equations yield accurate thermodynamic properties of pure as well as mixed refrigerants. Because of their high predictive power the BACKONE equations are a reliable tool for the application to many different pure and mixed refrigerants, especially if there is a lack of reliable data
The thermodynamic properties of the investigated pure and mixed refrigerants are computed by the BACKONE equation of state
Summary
Refrigeration systems are widely used in domestic and commercial applications.Approximately, there are three billion refrigeration systems used in the world which represent about17% of the electrical power consumption over worldwide [1]. Many researches have been conducted for improving the energy efficiency of these systems or to reduce their environmental effects. A minor enhancement in the system performance might have a significant effect on energy consumption. Many alternative refrigeration cycles were introduced to improve the cycle performance. These cycles may be different from the VCRC in their working principles such as the absorption cycle or might make changes in the cycle construction as the ejector, injection and cascade cycles. Alternative cycles tend to increase their energy efficiency and initial costs and working complexity. Computational simulations permit to carry out a comparison between different alternative cycles in a cheap and fast way, introducing various options, assisting to decide if Processes 2020, 8, 1017; doi:10.3390/pr8091017 www.mdpi.com/journal/processes
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