HEAT (MASS) TRANSFER AND FILM-COOLING EFFECTIVENESS WITH INJECTION THROUGH DISCRETE HOLES .2. ON THE EXPOSED SURFACE

The heat (mass) transfer coefficient and the film cooling effectivenes s are obtained from separate tests using pure air and naphthalene-satu rated vapor injected through circular holes into a crossflow of air. T he experiments indicate that Sherwood numbers around the injection hol e are up to four times those on a flat plate (without injection holes) due to the interaction of the jets and the mainstream. The mass trans fer around the injection holes is dominated by formations of horseshoe , side, and kidney vortices, which are generated by the jet and crossf low interaction. For an in-line array of holes, the effectiveness is h igh and uniform in the streamwise direction but has a large variation in the lateral direction. The key parameters, including transfer coeff icients on the back surface (Part I), inside the hole (Part I), and on the exposed surfaces, and the effectiveness on the exposed surface, a re obtained so that the wall temperature distribution near the injecti on holes can be determined far a given heat flux condition. This detai led information will also aid the numerical modeling of flow and mass/ heat transfer around film cooling holes.