Molecular dynamics investigation on shear viscosity of the mixed working fluid for supercritical CO2 Brayton cycle

Abstract

Effects of the impurity gas on CO2 shear viscosity has not been fully understood yet. In this work, the shear viscosity of CO2 + N2 + O2 and pure CO2 were calculated via molecular dynamics simulation and theoretical models. Compared with the NIST database, the relative deviation of the pure CO2 shear viscosity was below 1%. Then, effects of the impurity gas, namely N2 and O2, on the shear viscosity were discussed. The shear viscosity increased when CO2 was mixed with N2 and O2. The results demonstrated that the maximum relative change of the shear viscosity can reach 5.72% when the mole fraction of N2 and O2 in the system was 20% at 15 MPa and 827 K. Predicted shear viscosity in this work would guide the design and optimization of supercritical CO2 Brayton cycles.