The effects of dual-orifice air-ring design on blown film cooling

Numerical simulations of turbulent air flows tangentially impinging on blow n film bubbles have been carried out. The cooling air is assumed to origina te from a dual-orifice adjustable air-ring. The streamline patterns and hea t fluxes are determined through a finite volume numerical technique for mod eling of turbulent air flow. It is shown that cooling efficiency is critica lly sensitive to the air-ring design as minor modifications cause large var iations in cooling performance. Additionally, for a given design, the opera tional setup of the air ring is equally critical to the cooling performance . It is explained that the large influence observed on heat transfer rates is primarily due to the Coanda effect, which forces air jets to attach them selves to surfaces.