Thermodynamic investigation on the use of transcritical carbon dioxide in a reheat gas turbine-based combined cooling and power cycle

Abstract Currently, increasing the efficiency of power generation cycles is not the only goal for engineers; the focus is also on how it is achieved, whether through conventional or non-conventional energy sources. In conventional systems, changing the working fluid in the bottoming cycle has attracted engineers’ interest to boost cycle efficiency. Among various working fluids, carbon dioxide and ammonia water mixtures show promising thermodynamic properties that enhance both first and second law efficiencies. This research explores the use of transcritical carbon dioxide as the working fluid in the bottoming cycle of a combined cycle power plant with reheat cycles. The results indicate that, under operating conditions such as a topping cycle pressure ratio of 20, an ambient temperature of 303 K, and a turbine inlet temperature of 2000 K, the system performs better, with first law and second law efficiencies reaching 44.8% and 56.83%, respectively. Additionally, the maximum cooling water mass flow rate, observed at a condenser pressure of 0.9 bar, is 1.67 kg/s.