Simulation investigation of absorption refrigeration cycles using CO₂ as a refrigerant

Abstract As one kind of natural refrigerant, CO 2 has garnered significant in recent decades owing to its excellent thermodynamic properties and environmental friendliness. It has been considered the most competitive and potential green refrigerant compared to other natural refrigerants. On the other hand, Absorption technologies show great potential in utilizing renewable energy and waste heat. Therefore, trans-critical CO 2 absorption refrigeration is considered an attractive type of refrigeration solution and has been the subject of extensive research. In this study, the model of a single-effect trans-critical CO 2 /ionic liquid (IL) absorption refrigeration system (TsCO 2 -ARS) including one internal heat exchanger was established for the simulation in this study. Novel CO 2 -ionic liquid (IL) mixtures were selected as working pairs for the system to investigate the simulation and obtain its optimal operating conditions. Based on vapor-liquid equilibrium experiment data of CO 2 /ILs and Peng-Robinson equation of state (PR-EoS), circulation ratios of the system under different working conditions were calculated. The optimal circulation ratio was determined and under its working setting, the coefficient of performance, COP of single effect TsCO 2 -ARS was compared with the standard operation conditions. The results of this study can provide valuable insights for the design and optimization of CO 2 /IL mixture utilization trans-critical CO 2 absorption refrigeration systems with the internal heat exchanger.