Performance Study and Energy Saving Process Analysis of Hybrid Absorption-Compression Refrigeration Cycles

In an attempt to improve the performance of hybrid absorption and mechanical vapor compression refrigeration systems and to determine the fundamental reasons for such improvements, two configurations of the hybrid refrigeration cycle with a booster compressor at different positions of the cycle (between the evaporation and the absorber, or between the generator and the condenser) are simulated and analyzed. The interrelation between the two subcycles and the hybridization principle have been explored and clarified. An NH3/H2O-based hybrid cycle is the basis of this simulation. It was found that (1) the hybrid cycle performance is mainly governed by the interaction between its two subcycles of mechanical compression and thermal compression and their respective energy efficiencies, and (2) the hybrid cycle primary energy-based coefficient of performance (COP) was higher by up to 15% (without internal heat recuperation) as compared with the nonhybrid absorption cycle, (3) in comparison with the nonhybrid absorption and vapor compression cycles working in the same temperature regions, the more efficient use of low-temperature heat by cascade utilization of the two energy inputs (heat rate and mechanical power) with different energy quality, and the enhanced refrigeration ability of low-temperature heat are the basic reasons for the hybrid cycle performance improvement and significant energy saving, (4) the hybrid cycle achieves an exergy efficiency of 36.5%, which is 27% higher than that of the absorption cycle, and 4.5% higher than the vapor compression cycle, achieving a thermal-driving exergy efficiency of 37.5% and mechanical work saving ratio up to 64%.