Enhanced COP absorption refrigeration using R-1243zf/phosphonium based ILs with compression assistance for low-grade heat

This study investigates the novel working pair of R-1243zf paired with phosphonium-based ionic liquids (ILs), [P₆₆₆₁₄][Tf₂N] and [P₆₆₆₁₄][TMPP], for absorption refrigeration systems. Solubility of R-1243zf in both ILs was measured experimentally using the isochoric saturation method across temperatures ranging from 293.15 K to 343.15 K and pressures up to 0.95 MPa. Results show higher solubility in [P₆₆₆₁₄][Tf₂N] than in [P₆₆₆₁₄][TMPP], with both exhibiting increased solubility with pressure and decreased solubility with temperature. The NRTL model accurately correlated the data (avg. abs. dev. < 0.66%). Mixing enthalpies were also calculated. Thermodynamic performance of single-effect (SARS), Dual-effect (DARS), and compression-assisted (LC-SARS: low-pressure compressor, HC-SARS: high-pressure compressor, LC-DARS: low-pressure compressor assisted DARS) cycles was analyzed. Compression assistance significantly enhances Coefficient of Performance (COP) and reduces required generator temperatures. LC configurations outperformed HC configurations. R-1243zf/[P₆₆₆₁₄][Tf₂N] consistently achieved higher COP than R-1243zf/[P₆₆₆₁₄][TMPP] across all cycles. Thermal Energy Consumption Ratio (TECR) decreased while Electrical Energy Consumption Ratio (EECR) increased with compression ratio (CR). An optimal CR of 1.8 was identified for LC-DARS using R-1243zf/[P₆₆₆₁₄][Tf₂N] via TOPSIS analysis, balancing high COP (0.728) with a high Proportion of Thermodynamic Energy Consumption (PTEC=0.781). Among 9 screened ILs, phosphonium-based ILs generally yielded higher COP than imidazolium-based ILs in LC-DARS, attributed to higher R-1243zf solubility. It demonstrates the potential of R-1243zf/phosphonium-IL pairs, particularly R-1243zf/[P₆₆₆₁₄][Tf₂N] in LC-DARS with optimized compression, for efficient utilization of low-grade heat in integrated energy systems.