Performance optimization of absorption refrigeration systems using R-1233zd(E)/phosphonium ionic liquid working pairs

With global energy consumption surging and environmental concerns escalating, absorption refrigeration systems are receiving increasing attention. This study investigates the absorption behavior and thermodynamic performance of absorption refrigeration systems using trans -1-chloro-3,3,3-trifluoro-1-propene (R-1233zd(E)) paired with phosphonium-based ionic liquids (ILs), trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) amide ([P 66614 ][Tf 2 N]) and trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ([P 66614 ][TMPP]). Experimental solubility measurements of R-1233zd(E) in the ILs were conducted using an isochoric saturation method across a temperature range of 293.15–343.15 K and pressures up to 0.61 MPa. The Non-Random Two-Liquid (NRTL) thermodynamic model was employed to correlate solubility data, yielding excellent agreement with deviations of less than 3.84 %. Results revealed that [P 66614 ][TMPP] exhibits higher solubility due to its branched alkyl chains, increased free volume, and favorable van der Waals interactions. Thermodynamic analyses were performed for single-effect (SARS), double-effect (DARS), and compression-assisted cycles (LC-SARS, single-effect cycle with a compressor added in the low-pressure side; HC-SARS, single-effect cycle with a compressor added in the high-pressure side; LC-DARS, double-effect cycle with a compressor added in the low-pressure side). It demonstrated that [P 66614 ][TMPP] exhibits a higher coefficient of performance (COP) compared to [P 66614 ][Tf 2 N]. Compression assistance reduced the minimum generation temperature and improved COP by leveraging electrical energy. Among all configurations, LC-DARS with a compression ratio of 1.9 demonstrated the optimal balance between COP (0.82) and thermal energy utilization efficiency. These findings highlight the potential of R-1233zd(E)/[P 66614 ][TMPP] as a sustainable working pair for absorption systems, particularly in low-grade heat recovery applications.