An Improved Analytical Approach to Steam Turbine Heat Transfer

Abstract

Improvements to the design of advanced steam turbines require an improved understanding of the heat transfer within the various components of the unit. Physics-based ANSYS models for typical high pressure and intermediate pressure units have been developed. The boundary conditions were derived from full-load, steady state flow analyses, steam turbine performance code outputs and computational fluid dynamics (CFD) analyses to develop normalized (non-dimensional) local flow conditions, with the normalizing parameters based on key cycle parameters. These normalized local flow conditions and cycle parameters were then used to define local transient boundary temperatures and heat transfer coefficients for input to the thermal ANSYS model. Transient analyses of components were performed. The results were compared with temperature measurements taken during the operating cycle of an operational steam turbine to validate and improve the methodology and were applied to structural models of the components to predict their thermal growth and the net impact on the clearance between the rotor and diaphragms and other secondary flow paths in the steam turbine, including seals.