EFFECT OF STRONG CURVATURE INSIDE A TWO-PASS SERPENTINE PASSAGE

Abstract

In this study, we delve into the complex dynamics of thermo-fluid systems, highlighting applications in air-conditioning, heat exchangers, and the cooling pathways in gas turbine blades. These systems commonly incorporate a two-pass serpentine flow configuration with square or rectangular cross-sections. As fluids traverse these channels, they develop intricate three-dimensional structures. This complexity is primarily attributed to Dean-type secondary motions, coupled with phenomena like flow separation and impingement, particularly prevalent in areas of strong curvature. Our initial focus is on analyzing turbulent flow within a straight, square duct under pressure-driven conditions. Conducted at a high Reynolds number Re = 40,000, this part of the study aims to replicate conditions of fully developed turbulence. Using numerical simulations, we explore the secondary flow characteristics within the square duct, examining velocity and vorticity fields in detail. These findings are cross-referenced and validated with experimental published data. Significantly, the simulation results at Re = 40,000 revealed a consistent pattern of turbulence intensification and heat transfer enhancement in areas of flow reattachment. The secondary flow structures were observed to significantly influence the thermal boundary layer, leading to notable variations in heat transfer rates across different sections of the duct. These variations were closely correlated with the intensity and orientation of vortical structures. Building on these validated results, we extend our investigation to a square duct under a higher Reynolds number Re = 50,000. This step is crucial for aligning with the numerical requirements of our two-pass serpentine passage study, which necessitates an inlet condition of fully developed turbulence. This condition sets the stage for the fluid's entry into the strong curvature two-pass serpentine passage.