Performance investigation of a novel closed Brayton cycle using supercritical CO₂-based mixture as working fluid integrated with a LiBr absorption chiller

A novel closed Brayton cycle using supercritical CO₂–Kr mixture as working fluid integrated with an absorption chiller (CBC/AC) is proposed. The waste heat of the CO₂–Kr in the cold end of the top closed Brayton cycle (CBC) is utilized to drive the absorption chiller, which further chills the CO₂–Kr fluid exiting the precooler before it enters the main compressor. Compared with the stand-alone supercritical CO₂ (S-CO₂) CBC, the CBC/AC exploits the performance improvement potentials under low ambient temperature (T₀) condition and alleviates the performance penalty under high T₀ condition. The energy and exergy analyses of the CBC/AC in three typical T₀ conditions (10 °C, 25 °C and 40 °C) show that the thermal efficiencies are improved by 3.12%, 0.40% and 6.86%, respectively, the exergy efficiencies are improved by 3.53%, 0.54% and 7.53%, respectively. The exergy loss from the precooler is significantly reduced in the CBC/AC relative to that in the stand-alone S-CO₂ CBC. The comparisons between different working conditions for the CBC/AC indicate that the improvements of the thermal and exergy efficiencies are more apparent under water-cooling and high turbine inlet temperature conditions. The effects of the component performance on the CBC/AC are also evaluated.