EFFECT OF MIXED REFRIGERANT COMPOSITION ON PERFORMANCE OF AN AUTO-CASCADE REFRIGERATION SYSTEM USING R600a/R1150/R14.

A mathematical model based on energy and exergy methods is established to analyze the performance of an auto-cascade refrigeration system at varying compositions of the mixed refrigerants, condensation temperature, evaporation temperature, and vapor quality at the condenser outlet. Furthermore, grey correlation theory is employed to assess the correlation degrees between refrigerant mass fractions and system performance, enabling the identification of the state that has the greatest impact on the output parameters. It has been concluded that while maintaining a constant mass fraction of R600a, an increase in the mass fraction of R1150 (State 1) leads to a higher cooling capacity but a decrease in exergy efficiency. The performance decreases with the increase of the R600a mass fraction (State 2) as the R1150 mass fraction is unchanged. When the component of R14 is constant while the other two components R600a/R1150 vary (State 3), and the COP exists as the optimal value. The mixture of R600a/R1150/R14 with a mass fraction of 0.5:0.2:0.3 has better performance at COP of 0.5027 and exergy efficiency of 29.43% under a condensation temperature of 30 °C. Based on the results of the grey correlation degree, the greatest factor in cooling capacity is State 1, while the COP and exergy efficiency are primarily controlled by State 3. [ABSTRACT FROM AUTHOR]