Utilizing the waste heat in EETC CO۲ cycle by means of single-effect absorption refrigeration cycle

Present work is an attempt to investigate on the performance of combination of ejector-expansion transcritical cascade (EETC) CO۲ cycle with a singleeffect absorption refrigeration cycle. For thermodynamic reasons, the CO۲ entering the gas cooler has a great potential to be used in bottom cycles. The aim of proposing combined system, in this work, is an attempt to capture the waste heat in the gas cooler. In addition, proposed combined system can be accounted as the best effort to achieve wide ranges of cooling effect simultaneously. Using a constant-area mixing model for the ejector and on the basis of first and second laws of thermodynamics, an optimization of system has been performed. Also exergy analysis is carried out in order to show the irreversibility distribution within the system and the contribution of different components to the exergy destruction in the cycle. Results indicate that increasing the generator temperature from ۶۷oC to ۱۰۵oC results in an increase of the COP and second law efficiency of the cycle by up to ۵۶.۵% and ۷۳.۵%, respectively. In addition, results show that an increase in the cooling capacity ratio increases both the COP and exergy efficiency of the proposed system. Exergy analysis reveals that compressor and ejector have the first and second highest contribution of exergy destruction in the cycle, respectively.

Keywords:

Ejector , transcritical CO۲ , absorption refrigeration , COP , Exergy destruction