Flow impingement onto a flat plate with limited heated area in relation to laser gas assisted processing: Influence of nozzle geometry on heat transfer rates

The purpose of this paper is to investigate the influence of conical and annular nozzle geometric configurations on the flow structure and heat transfer characteristics near the stagnation point of a flat plate with limited heated area. The governing equations of flow and heat transfer are modeled numerically using a control and volume approach. It is found that nozzle exiting velocity profiles differ considerably with changing the nozzle cone angle. Increasing nozzle cone angle enhances the radical flow and extends the stagnation zone away from the plate surface. The impinging jet with a fully developed velocity profile results in enhanced radical acceleration of the flow. Moreover, the flow structure changes considerably for annular conical and conical nozzles. The nozzle exiting velocity profile results in improved heat transfer coefficient at the flat plate surface. However, the achievement of fully developed pipe flow like velocity profile emanating form a nozzle is almost impossible for practical laser applications.