Performance analysis of double-effect absorption refrigeration systems using hydrofluoroolefin refrigerants and ionic liquid absorbents

This study investigated the feasibility of double-effect absorption refrigeration systems (DEARS) using hydrofluoroolefin (HFO) refrigerants and ionic liquid (IL) absorbents as working fluid pairs. Enthalpy and vapor-liquid equilibrium (VLE) correlation equations were developed to facilitate thermodynamic modeling and system analysis. Among the examined pairs, R1234ze(Z) + [BMIM][SCN] and R1336mzz(Z) + [OMIM][BF4] were identified as promising candidates due to their significant concentration differences between weak and strong solutions (0.0998 and 0.0565, respectively). Performance evaluations demonstrated high coefficients of performance (COP), reaching 1.24 for R1234ze(Z) + [BMIM][SCN] and 1.46 for R1336mzz(Z) + [OMIM][BF4]. Further analysis of COP variations under different operating conditions reveals that both working fluid pairs exhibit performance improvements with increasing generator temperatures. The absorber temperatures significantly influenced system efficiency, where lower temperatures enhanced refrigerant separation and improved COP. Similarly, increasing the evaporator temperature improved COP by raising the saturation pressure, which enhanced refrigerant separation in the generator and overall system performance. These findings expanded the selection of environmentally friendly refrigerants for DEARS by incorporating ILs, contributing to the sustainable development of absorption refrigeration systems.