Numerical investigation of heat transfer characteristics of an axi-symmetric turbulent impinging jet on a flat plate

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.

Jet impingement is one of the oldest and most attractive techniques for convective process intensification where convective heating, cooling or drying is applied The present study highlights the numerical study of heat transfer characteristics of Axi symmetric incompressible Impinging Jet flow. A computational study of the impingement of a thermally turbulent jet on a solid plate has been reported. For a fixed nozzle-plate distance, the influence of the Reynolds number on the stagnation point heat transfer was investigated. The influence of the nozzle-plate distance on the stagnation point Nusselt number has also been discussed. The possibility of improving the heat transfer is carried out according to the characteristic parameters of the interaction jet and wall. At higher Reynolds numbers and even for initially laminar jets - the turbulence generated by the jet itself plays an important role in determining the heat­ transfer characteristics of impinging jets. The effect of local mean velocities and turbulence intensities on the heat transfer has been outlined, whereas the objectives of this part is to explore in more detail the influence of the turbulence characteristics of the flow on heat transfer. In a jet flow, vortices initiate in the shear layer due to Kelvin Helmholtz instabilities. Vortices, depending on their size and strength, affect the heat spread, the potential core length and the entrainment of ambient fluid A very important parameter in order to quantify this process is the heat transfer coefficient The enhancement and reduction of the local heat transfer were related to changes in the flow structure which an impinging jet was forced at different frequencies. It is important, therefore, to understand the unsteady heat transfer characteristics associated with the coherent flow structure.