Photochemical Properties of trans-1-Chloro-3,3,3-trifluoropropene (trans-CHCl═CHCF3): OH Reaction Rate Constant, UV and IR Absorption Spectra, Global Warming Potential, and Ozone Depletion Potential

The aim of this study is to investigate the effect of low global warming potential refrigerants on the optimum intermediate pressure (POPT,int) and performance (COP) values of a refrigeration system with flash intercooling. For realize, the optimum operating parameters of system were determined in low temperature applications through a theoretical analysis according to the different refrigerants (R290, R404A, R407C, R507A, and R22). The theoretical modelling of system is done by optimizing the intermediate pressure at given evaporation (TE) and condensation (TC) temperatures for selected refrigerants. After optimization, the maximized values of COP and Second law efficiency are computed from the predicted values of POPT,int . The linear regression method is then used to derive three correlations of POPT,int , maximum values of COP and Second law efficiency according to TE and TC. Hence, the POPT,int values maximizing the system performance are found from various TE and TC values for each refrigerant. Due to calculations, increasing TE and TC cause the increase in POPT,int in low temperature applications. The R507A system has the highest POPT,int values and R22 system has the lowest POPT?int values. Although R22 system has slightly more efficient than R290 system, it is being phased out world?wide because of the risk of ozone depletion potential and global warming potential considerations. Therefore, it is important to evaluate the R22 replacement options. The R290 was discovered to have better performance than the R404A, R407C and R507A systems in terms of COPmax (1.81), global warming potential (11), and ozone depletion potential (0) when TE and TC are -35?C and 40?C.

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A Study Initiated because of the Global Warming from R-134a

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.837.751 ◽

2013 ◽

Vol 837 ◽

pp. 751-756

Author(s):

Feiza Memet ◽

Daniela Elena Mitu

Keyword(s):

Global Warming ◽

Global Warming Potential ◽

Ozone Depletion ◽

Exergy Analysis ◽

Coefficient Of Performance ◽

Working Fluid ◽

R 134A ◽

Vapour Compression ◽

Ozone Depletion Potential ◽

Depletion Potential

Vapour compression cycles are commonly used in household refrigerators and also in many commercial and industrial refrigeration systems. R-134a is a working fluid widespread in this kind of systems. A chlorine free refrigerant such as R-134a has a disadvantage in the sense of its relatively high Global Warming Potential (GWP), although the specific Ozone Depletion Potential (ODP) is null. International concern over the relatively high global warming potential of R-134a, and other refrigerants belonging to the same family, will lead in the near future to the stop of their production and use. For this reason, the interest in finding of an environmental more benign substitute for this refrigerant is growing. In the meantime, the alternatives for R-134a should be as thermodynamically attractive as this chemical. In this study it is theoretically assessed the opportunity of using R-600a (isobutane) in the future environment friendly vapour compression refrigeration systems. Choosing of isobutane is explained by the fact that it is a naturally occurring refrigerant. During the thermodynamic analysis, R-134a and R-600a are evaluated for a range of evaporating temperatures starting with 25°C and finishing with 0°C. There are considered three levels of the condensing temperature: 30°C, 40°C, 50°C. For these two refrigerants are compared results regarding saturated vapour pressure, Coefficient of Performance, volumetric cooling capacity, compressor discharge temperature, refrigerant mass flow rate. Also, in the scope of future improvement of systems adopting R-600a as a refrigerant, it is performed an exergy analysis, which is able to reveal the hierarchy of inefficiencies in the system. The results obtained indicate that adopting of R-600a instead of R-134a in vapour compression refrigeration systems is a decision motivated not only by environment reasons, but also by thermodynamic arguments. Values for the Coefficient of Performance when using R-600a are slightly lower than when in use is R-134a, but isobutane offers better environmental requirements like zero Ozone Depletion Potential and very low Global Warming Potential. Exergy analysis developed for R-600a as a working fluid revealed that the most inefficient is the compressor. Better exergy efficiency can be obtained for higher values of the evaporating temperature.

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