Flow and heat transfer characteristics of impinging jet from notched orifice nozzle

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 to the downstream and reaches to the maximum of 1.2 times of the nozzle exit maximum velocity at about x/d0=2 (d 0: nozzle exit diameter), this is also effective to enhance the heat transfer performance of impinging jet. In order to reduce the flow resistance remaining a vena contract effect, use of a cone orifice nozzle has been considered. 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. Moreover, heat transfer performance of the impinging jet from an orifice nozzle is made clear and the improvement or enhancement by a notched orifice nozzle and a tapered notched nozzle will be shown by experimental research works.