A two-equation turbulence model with additional terms for Coriolis and rotational buoyancy has been used for prediction of heat transfer from the leading and trailing sides of rotating square and rectangular channels with radially outward flow. Test cases with different Reynolds and rotation numbers are considered. The coolant air used is pressurized and operating conditions are selected to closely match real turbine operating parameters. Results show that previous experimental data can be extrapolated to predict the heat transfer characteristics of coolant passages of actual turbine blades. The internal secondary flow vortex structures for some of the aspect ratio channels are found to be different from the expected vortex structures based on earlier lower rotation speed, lower temperature, and lower pressure operating conditions.