Experimental and numerical investigations of transient conjugate heat transfer processes

Abstract

Effective cooling of components exposed to high thermal loads is a key challenge in aircraft engine development. Analyzing thermal loads during flight missions is critical, as they fluctuate with varying operating conditions. Accurate assessment requires considering coupled heat transfer processes and transient effects. The calculation of slow, transient phenomena was optimized by enhancing a coupling environment between a finite element and a finite volume solver. A wide range of boundary conditions and geometries were experimentally investigated. An existing ITLR test rig was adapted, and four geometries were examined. The rig enables independent, reproducible control of inlet velocity and temperature, allowing the study of various test cycles. Wall temperatures were measured with high resolution using infrared thermography, and wall heat fluxes were calculated. Numerical simulations complemented the experiments. The data support validation of the coupling environment and showed good agreement with simulations. A variable, adaptive, experiment-specific coupling step size reduced computation time while preserving accuracy. A method was developed to enhance prediction accuracy and account for local dissipation, targeting heat transfer coefficients and friction factors in complex flows. Experimental data were analyzed using heat transfer correlations. A close relationship between two local parameters was observed, which enabled the development of a simplified correlation. The resulting model included coefficients that could be linked to established laws for turbulent boundary layer flows. One parameter correlates with local pressure gradients, near wall streamlines and friction factor distributions, while the other yields a Reynolds analogy factor that was used to estimate wall shear stresses. The model agreed well with simulations and proved universally applicable.