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

Abstract

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.