An exergy analysis of cascade refrigeration system with R744 and R717 is presented in this paper to optimize the design and operating parameters of the system. The design for the operating parameters considered in this study include superheating and subcooling degree, cascade heat exchanger and compression efficiency, condensation and evaporation temperature in the R717 high temperature cycle and R744 low temperature cycle, respectively. The main results are summarized as follows : As the cascade evaporation temperature increases, the COP of R717 high temperature cycle increases. But the COP of R744 low temperature cycle decreases, and the COP of total cascade cycle is almost constant. As cascade evaporation temperature increase, the exergy loss in the R717 condenser and the R744 cascade heat exchanger is the largest and the lowest among all components, respectively. Therefore, in order to improve the COP of total cascade cycle and exergy efficiency ( ) of cascade refrigeration system with R744 and R717, the exergy loss of the condenser and compressor of R717 must be reduced.

Abstract
1. 서 론
2. 성능 분석
3. 결과 및 고찰
    3.1 성능계수의 비교
    3.2 이론과 실제 성능계수의 비교
    3.3 엑서지 분석
4. 결 론
References

• 강동훈(Dept. of Mechanical System Engineering, Graduate School, TongMyong Univ.) | Dong-Hun Kang
• 구학근(Professor, Dept. of Refrigeration and Air-Conditioning Eng., TongMyong Univ.) | Hak-Keun Ku Corresponding author