Thermodynamic Analysis of One Kind of Single-stage with Expender and Four Kinds of Two-stage Transcritical Carbon Dioxide Refrigeration Cycle

Abstract

The performances of single-stage transcritical CO2 cycle with expander, transcritical CO2 two-stage cycle without intermediate heat exchanger, transcritical CO2 two-stage cycle with intermediate heat exchanger, transcritical CO2 two-stage & primary throttling cycle without intermediate heat exchanger and transcritical CO2 two-stage & primary throttling cycle with intermediate heat exchanger are analyzed in refrigeration condition. The results show that the single-stage expander cycle outperforms the other options when the expander efficiency is 60% at the given evaporation temperature (﹣10 ℃~20 ℃). When the evaporation temperature is 5 ℃ and the expander efficiency is greater than 32% , the performance of expander cycle is the best. In the other four two-stage cycles, transcritical CO2 two-stage cycle without intermediate heat exchanger and transcritical CO2 two-stage cycle with intermediate heat exchanger are reasonable options in medium and high evaporation temperature, and the performance of using internal heat exchanger in cycle is much better; transcritical CO2 two-stage & primary throttling cycle without intermediate heat exchanger and transcritical CO2 two-stage & primary throttling cycle with intermediate heat exchanger are more applicable to medium and low evaporation temperature. And the using of internal heat exchanger decreases the cycle performance.

Keywords

• expender
• carbon dioxide
• transcritical cycle
• two-stage
• single-stage