Performance Study and Energy Saving Mechanism Analysis of an Absorption/mechanical Hybrid Heat Pump Cycle

A hybrid heat pump cycle of the heat amplifier type integrating a booster compressor between the generator and the condenser for distributed heating is simulated and analyzed. The interrelation between the two sub-cycles and the hybridization principle are explored. The theoretical analysis is demonstrated by a H2O/LiBr based hybrid cycle simulation. Investigation of the interaction mechanisms between the mechanical compression and absorption has shown that there is an optimal compression ratio of about 1.2-1.8 for which the low-temperature driving heat can be utilized most effectively (giving highest coefficients of performance). A study was also carried out to reveal the energy saving mechanism in the hybrid system as compared with an individual absorption heat pump and a simple vapor compression heat pump working within the same temperature regions. The results indicate that replacement of a part of the mechanical work with low-grade heat makes the hybrid cycle achieves not only significant energy saving of high-quality mechanical work, but also better use of low-grade waste heat because of the cascade use of the two energy inputs. The coefficient of performance (based on both power and heat input) and heat driving coefficient of performance in the hybrid cycle are found to be improved by 10.2% and 16.6%, respectively, in comparison with separate absorption and vapor compression systems.