This report is divided into four parts. First part of the report describes the methods used to measure and model the flow of supercritical carbon dioxide (S-CO 2) through annuli and straightthrough labyrinth seals. The effects of shaft eccentricity in small diameter annuli were observed for length-to-hydraulic diameter (L/D) ratios of 6, 12, 143, and 235. Flow rates through toothcavity labyrinth seals were measured for inlet pressures of 7.7, 10, and 11 MPa with corresponding inlet densities of 325, 475, and 630 kg/m 3. Various leakage models were Pressure Ratio Mass Flow Rate (kg/s) Experiment Experiment HEM HEM Const. C d HEM Const. C d HEM Approach-26 0 C Approach-26 0 C Approach-24.5 0 C Approach-24.5 0 C Approach-18.2 0 C Approach-18.2 0 C Approach-14.3 0 C Approach-14.3 0 C Approach-9.8 0 C Approach-9.8 0 C Approach-7.2 0 C Approach-7.2 0 C Approach-5.1 0 C Approach-5.1 0 C m makeup [Kg/s]