Numerical Prediction of the Second Peak in the Nusselt Number Distribution from an Impinging Round Jet

Abstract

The results of numerical simulations of a single impinging round jet, using different numerical parameters are presented. To simulate the heat transfer in industrial drying with arrays of different jets the heat transfer for a single round jet (Re=23000 based on jet’s diameter and bulk velocity and the dimensionless jet’s outlet to target wall distance= 2) is used as a test case to validate the numerical model. The distribution of the Nusselt-number serves as a benchmark and the computational cost with regard to CPU-time and memory requirements should be minimal. To accurately predict the intensity and position of the secondary peak from an impinging flow, different approaches for turbulence modeling are considered and their results are compared with data from the literature. The influence of the grid size and the grid shape is analyzed and the grid-independent solution is determined. The results using different implementations of the SST k-omega model, as the best compromise between the computational cost and accuracy are compared. Low Re damping modification in the implementation of SST K-ω has an important role in the prediction of the secondary peak. Good results can be achieved with a coarse grid, as long as the boundary region is appropriately resolved. Polyhedral grids produce good quality results with lower memory requirements and cell numbers as well as shorter run times.