Abstract:

A novel combined power and refrigeration system coupled with a trans-critical carbon dioxide (TCO₂) recompression cycle and an ejector refrigeration cycle is proposed, which produces power output and refrigeration by utilizing low-grade thermal energy discharged from the CO₂ recompression cycle. The performance of combined cycle was compared with that of recompression cycle, and an exergy and parametric analysis was performed to evaluate the effect of key thermodynamic parameters on the performance of the combined cycle. The results show that because of the utilizing of waste heat from CO₂ which drives the ejector to generate cooling capacity, thermal efficiency of the combined cycle is higher than that of the recompression cycle. The biggest exergy loss occurs in the heater and the heat regenerator came second. It is also shown that the turbine inlet pressure, inlet temperature and back pressure have significant effect on the mass flow rate, turbine power output, power consumption of compressor, refrigeration output and thermal efficiency of the combined cycle. However, the condenser temperature and the evaporator temperature only have remarkable influences on the refrigeration output of the ejector refrigeration cycle. The thermal and exergy efficiency of the combined cycle are severally 46.99% and 47.21% under the given condition.

Key words: trans-critical carbon dioxide (TCO₂), recompression cycle, ejector refrigeration, combined power and refrigeration