Numerical Study of Turbulent Confined Jets Impinging on a Heated Substrate for Thin Film Deposition

Abstract

This paper reports on the study of confined jets and jets interaction in terms of increasing chemical transport. The context of this study is the atmospheric pressure plasma-enhanced chemical vapor deposition, higher thin film growth rate being desired, while maintaining total flow rate as low as possible. Turbulence mixing and enhanced heat transfer are the physical mechanisms identified as being capable of increasing the growth rate at atmospheric pressure. A numerical study of jets impinging on a heated substrate was carried out using quasicompressible Reynolds-Averaged Navier–Stokes (RANS) equations. Abe–Kondoh–Nagano (AKN) low-Reynolds k-ε and standard k-ε models were tested using an unconfined impinging jet at Reynolds number Re = 23,750 for jet diameter to plate-spacing ratios of H/d = 2 and H/d = 6. Results were compared with experimental data from the literature. Based on numerical results and in accordance with existing findings, the AKN low-Reynolds k-ε was shown to be reasonably accurate and was thus chosen for the numerical study. The effects of flow rate, hole diameter and length, jet-to-jet spacing, confinement width, and jet number were investigated numerically for inline jets confined between two vertical planes for jet Reynolds numbers between 810 and 5060. The configurations with the greatest turbulent intensity were studied, with the addition of diluted species transport and consumption. A laminar flow setup with a slot jet (Re = 79.5) was compared to two injection designs consisting of a simple set of 12 impinging gas jets (Rej = 2530; H/d = 3) with and without the adjunction of a wire to break the jets (Rej = 1687; H/d = 2). The two turbulent injection methods improved growth rate by 15%, which mainly resulted from a larger gas heating by the surface due to turbulent heat exchange in the jet impact zone.