Abstract
Jet flow from an orifice nozzle is applicable to mixing and entraining of ambient fluid effectively because of a large shearing stress layer with a large velocity gradient at the jet edge due to the vena contracta effect, but the sudden contraction at the nozzle exit accounts for a large flow resistance. The centerline velocity increases in the x direction from the nozzle exit and reaches to the maximum of 1.2uce (where, uce is the nozzle exit maximum velocity) at x/d0≈2 (where, d0 is the nozzle exit diameter), this may be also effective to enhance the heat transfer performance of impinging jet. In order to reduce the flow resistance remaining a good mixing performance caused by the vena contract effect, use of a cone orifice nozzle has been considered. Moreover, to increase the turbulence for improvement of mixing properties the use of tab, lib, and notch for orifice nozzle is thought. In this study, the effects of use of a notch for the orifice nozzle on the flow characteristics are examined experimentally. Hot wire measurements were conducted to demonstrate the spreading or mixing performance of the notched orifice nozzle having a reduced flow resistance of the nozzle and an increasing turbulent intensity more than that for a conventional orifice nozzle.
