The comparison between C02/NH3 and C0~1234yf for optimal condensing temperature in cascade refrigeration systems

Nowadays industries use C02/NH3 cascade refrigeration systems for deep cooling,
down to - 50°C. Even though it is compatible with the environment, it has an adverse
impact on human beings. In this work, an alternative combination of refrigerants,
namely C02/R123yf, is investigated for a cascade refrigeration system which has no
adverse effects, either on health or environment. This study performs a
thermodynamic analysis and compares two refrigerant pairs C02/NH3 and
C02/R1234yf, to determine the optimal condensing temperature of the cascadecondenser
using various design parameters which are evaporating temperature,
condensing temperature and intermediate temperature difference in order to
maximize the COP. Theoretically, the optimal condensing temperature of the
cascade-condenser increases with the condensing temperature, the evaporating
temperature and the temperature difference. On the other hand, the maximum COP
increases with the evaporating temperature but decreases as the condensing
temperature or difference temperature increases. The comparison between C02/NH3
and C02/R 1234yf for thermodynamic analysis of optimal condensing temperature in
cascade refrigeration system will give broad understanding of the safer refrigeration
system.