Calculations of fluid flow and heat transfer in expanding ducts

Abstract

A Numerical study is performed examining turbulent separated flow and heat transfer characteristics in axisymmetric expanding ducts, with emphasis to the annular diffuser geometry. The method is based on the fully conserved control volume representation of fully elliptic Navier-Stokes and Energy equations in body-fitted orthogonal curvilinear coordinate system. Turbulence is simulated via the two-equation (k-e) model. The presented results consist of computed velocity and streamline distributions, the kinetic energy of turbulence, and local and average Nusselt distributions. Systematic variations are made in the Reynolds number (6x10³ - 6x10⁵) and the outer wall half angles (7° -20°, 90°). The study was further extended to flows with a range (0.0-0.9) of inlet swirl. Comparison with available experimental data shows that the method with the utilized turbulence closure model and the discretization scheme reproduce the essential features of various diffuser heat transfer and fluid flow effects observed in the experiments.