Analysis of a Dual Recuperated Dual Expansion Supercritical CO2 Cycle for Waste Heat Recovery Applications

Superior performance and compactness of supercritical CO2 power cycles are encouraging researchers to explore them for waste heat recovery (WHR) applications. This paper presents a comprehensive thermodynamic analysis of a dual recuperated dual expansion cycle utilizing industrial waste heat. The proposed cycle incorporates two recuperators and two turbines with a single compressor. The influence of operating parameters concerning cycle performance in the context of a WHR cycle is discussed. The low side, high side pressures, and the split ratio between the high-temperature and low-temperature turbines are optimized for maximum power rather than thermodynamic cycle efficiency. The cycle performance is evaluated with air as the primary heat transfer fluid in the waste heat recovery heat exchanger operating at a maximum source temperature of 500 °C. The sink temperature is assumed to be 40 °C to enable operation in tropical conditions like India. The paper also compares the performance of the proposed WHR cycle with the baseline single recuperated sCO2 cycle operating under similar conditions. The analysis shows that the proposed cycle is able to extract 60% more heat and produce 37% more power than the single recuperated sCO2 cycle. The maximum heat recovery factor for the analyzed WHR cycle is 17.4%, compared to 12.7% for the single recuperated sCO2 cycle.