11th European Conference on Turbomachinery Fluid dynamics & Thermodynamics
HEAT TRANSFER & COOLING
Internal cooling channels of turbine blades are rib-roughened to increase the heat transfer between the wall and the coolant. A large effort has been made in simulating these flows with large eddy simulations to have a better understanding of the flow physics. This contribution focuses on the thermal prediction capabilities of large eddy simulations for such cooling channels. Of particular interest to this study is the influence of the thermal boundary condition on the heat transfer coefficient. If important, this strongly indicates that conjugate effects exist that would need to be modeled resulting in significant additional computational cost. Studies were carried out for Reynolds numbers of 40,000 at different thermal uniform heat flux boundary conditions. The results are compared with experimental aerodynamic and thermal data obtained at the von Karman Institute for Fluid Dynamics. The main outcomes are: first, the results show the dependence of the heat transfer coefficient on the imposed thermal boundary condition, even though it is usually assumed in experimental and numerical studies to depend only on the aerodynamics; this assumption may not be valid. Second, the dependence of the heat transfer coefficient on the thermal boundary condition implies that conjugate heat transfer is important for the current configuration and can be captured numerically, although research on fully coupled, efficient large eddy simulations based conjugate heat transfer algorithms is still needed.