Entropy Production and Energy Loss in Supercritical CO<sub>2</sub> Centrifugal Compressor

In Brayton cycle energy storage systems powered by supercritical carbon dioxide (sCO2), compressors are among the most critical components. Understanding their internal flow loss characteristics is, therefore, essential for enhancing the performance of such systems. This study examines the main sCO2 compressor from Sandia Laboratory, utilizing entropy production theory to elucidate the sources and distribution of energy losses both across the entire machine and within its key flow components. The findings reveal that turbulent viscous dissipation is the predominant contributor to total entropy production. Interestingly, while the relative importance of the entropy produced by various sources as the mass flow rate rises remains essentially unchanged, the total entropy production exhibits a non-monotonic trend, first decreasing and then increasing with the mass flow rate. High entropy production in the impeller is primarily concentrated in the clearance region and along the rear cover of the impeller tip. In the diffuser, it is most pronounced on the front and rear plates and within the central flow path. Meanwhile, in the volute, the highest entropy production occurs around the diffuser outlet and along the outer region of the volute’s centerline.