Abstract :
The performance of two stage cascade refrigeration system and irreversibility of the system is analysed for
different refrigerant pairs. Refrigerants R-134a, R-404A, R-152a are used in high temperature circuit and R508B &
R23 are used in low temperature circuit. The various working parameters are evaporating temperature (-50°C to -
70°C), condenser temperature (30°C to 50°C) and temperature difference in cascade condenser (4°C to 10°C). The
degree of condenser sub-cooling and evaporator superheat are assumed as 5°C and 7°C respectively, for all cases.
The isentropic efficiencies of the compressors are expected to be equal. The analysis shows that an increase in
evaporating temperature (TE), results increase in COP and decrease in irreversibility of the system. An increase in
condenser temperature (TC), results decrease in COP and increase in irreversibility of the system. An increase in
temperature difference in cascade condenser (ΔT), results in decrease in COP and increase in irreversibility of the
system. It is found that R134a – R23 has the maximum COP and low irreversibility of the system followed by R134a
– R508B among all the considered refrigerants. R134a – R23 pair has maximum COP which is 7.8% more than
R134a – R508B. R134a – R23 pair has less irreversibility which is 17% less than R134a – R508B.
Keyword :
Cascade, Refrigerants, COP, Irreversibility.