CO₂ based power cycle with multi-stage compression and intercooling for low temperature waste heat recovery

For low temperature waste heat recovery, CO₂ is preferred as the working fluid due to its low critical temperature and easy availability. However, a major limitation of CO₂ based power plant with low temperature waste heat recovery is temperature of heat rejection. In the present work, a study has been made to explore possible improved performance of a CO₂ power cycle using low temperature waste heat through multi-stage compression and intercooling. A thermodynamic model has been developed to analyze effects of various operating parameters on the performance of a CO₂ power cycle with two or more stages of compression and intercooling. Most significant observation is the existence of an optimum combination of the lowest cycle pressure and the intermediate pressure for either maximum specific power output or 2nd law efficiency of the CO₂ power cycle with two-stage compression and intercooling. - Highlights: • A model of multi-stage CO₂ Brayton cycle with intercooling is developed. • Both energy and exergy analyses are done. • For two-stage compression an optimum combination of LP and IP exists. • Gains in work output and 1st law efficiency are marginal beyond some stages.