EVALUATION OF THE PERFORMANCE OF MULTIPLE SUPERCRITICAL CO2 POWER CYCLES IN WASTE HEAT RECOVERY APPLICATIONS

Abstract

This paper aims to systematically evaluate the common supercritical carbon dioxide power cycles that are suitable for low to high grade waste heat recovery applications, with source temperatures ranging from 450 to 850 °C. A number of cycles varying from the simple to the fully cascaded split cycles are investigated against a predefined waste heat source for multiple temperatures and flow rates with a target power net yield of the order of 1 MWe. The conditions at the inlet to the main compressor in the sCO2 loop are also varied to quantify the role of the environmental heat sink in effective heat recovery. The sCO2 cycle parameters including the mass flowrate and split ratio as well as the effectiveness of the individual heat exchangers are optimized for multiple pressure ratios. Additionally, a detailed exergy analysis is conducted to identify the sources of entropy generation in the various components and enable a detailed comparison of the various cycle configurations reviewed. Improving the quality of the heat source from 450 to 850 °C yielded ~30% increase in cycle performance, while degrading the heat sink quality from 15 to 35 °C reduced the net output power by ~30%. The cascaded and split cycles were determined to achieve the highest performance across all conditions considered.