Heat Transfer of Impinging Jet: Effect of Compressibility and Turbulent Kinetic Energy Production

The effects of air compressibility, viscosity, and turbulent kinetic energy production modeling are studied in the case of round high-speed subsonic
wall impinging jet heat transfer. A vorticity based turbulence kinetic energy production term is implemented in the k-ω-SST model and the implementation is validated with experimental data. Compressible flow model results are compared with incompressible flow model results for more than 80 cases with pressure ratios up to 1.65 (Ma ≈ 0.85). The practical application considered in the present paper is the cooling section of a glass tempering machine. The vorticity based model performs better near stagnation point and second peak. The peak values affect visual quality of tempered glass through residual stresses. Glass initial temperature in the cooling section is about 600 oC and high-speed jets are produced with 1-3 mm nozzles. Validation is done with larger nozzles and slower jets as no suitable experimental data is available. The mean and maximum heat transfer rate resulting from choosing a constant viscosity at glass temperature and using an incompressible flow model differs less than 20 % from the compressible model results with locally modelled viscosity in all the studied cases. All the modeling is done with OpenFOAM and the modified code is published in GitHub.