A two-stage absorption–transcrtical hybrid refrigeration system is investigated in detail in this context. R744 is chosen for its transcritical subsystem and LiBr-H2O pair for the absorption refrigeration subsystem. The COP_(net) (A ratio of cooling capacity powered by low-grade heat to the low-grade heat consumption for the hybrid system) and COP_(mt) (A ratio of cooling capacity powered by mechanical work to the mechanical work consumption for the hybrid system) are proposed to evaluate performance of the hybrid refrigeration system. Firslty, a steady-state model has been developed to describe the hybrid system more realistically. The model is validated by the comparisons between the simulation results and the experimental data, which had been published in literature. It is deduced that the average deviation of COP_(net) is about 7.4% and that of COP_(mt) is about 8.5%. Then, based on the model of this novel system, main operating parameters are discussed on effects of COP_(net) and COP_(mt). Finally, from the simulation results, the hybrid system shows the huge potential in the utilization of low-grade heat with temperatures of 45～55°C.
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