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    An algorithmic approach towards finding better refrigerant substitutes of CFCs in terms of the second law of thermodynamics
    (Pergamon-Elsevier Science Ltd, 2005) Arcaklıoğlu, Erol; Çavuşoğlu, Abdullah; Erisen, Ali
    In this study, rational efficiency (RE) and component based irreversibility ratios of a cooling system based on the second law of thermodynamics using HFC and HC based pure refrigerants, such as, R32, R125, R134a, R143a, R152a, R290, R600a and their binary and ternary mixtures, along with R12, R22 and R502 (i.e. CFCs) have been numerically calculated. The effect of temperature glide, occurring at the condenser and evaporator, on the RE of the cooling system has been evaluated. The calculations are based on a constant cooling load on a cooling system with suction/line heat exchanger (SLHE). To be able to calculate the performance of the cooling system, an algorithm that uses the state point properties provided by REFPROP has been employed. We have targeted finding better mixture substitutes in terms of rational efficiency. For example, despite the suggestions in the literature; for R22, the mass percentage level of 20/80 of R32/R134a has provided the best RE level. The highest irreversibility (in percentages) is found at the condenser. The results also suggest that for both binary and ternary mixtures, a general trend of increases in RE level is observed against temperature glide increases occurring at this system component. (C) 2004 Elsevier Ltd. All rights reserved.
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    Thermodynamic analysis of refrigerant mixtures for possible replacements for CFCs by an algorithm compiling property data
    (Pergamon-Elsevier Science Ltd, 2006) Arcaklıoğlu, Erol; Çavuşoğlu, Abdullah; Erisen, Ali
    In this study, we formed an algorithm to find refrigerant mixtures of equal volumetric cooling capacity (VCC) when compared to CFC based refrigerants in vapor compression refrigeration systems. To achieve this aim the point properties of the refrigerants are obtained from REFPROP where appropriate. We used replacement mixture ratios-of varying mass percentages-suggested by various authors along with our newly formed mixture ratios. In other words, we tried to see the effect of changing mass percentages of the suggested (i.e. in the literature) replacement refrigerants on the VCC of the cooling system. Secondly, we used this algorithm to calculate the coefficient of performance (COP) of the same refrigeration system. This mechanism has provided us the ability to compare the COP of the suggested refrigerant mixtures and our newly formed mixture ratios with the conventional CFC based ones. According to our results, for R12 R290/R600a (56/44) mixture, for R22 R32/R125/R134a (32.5/5/62.5) mixture, and for R502 R32/R125/R134a (43/5/52) mixture are appropriate and can be used as replacements. (c) 2005 Elsevier Ltd. All rights reserved.