Measurements of mass transfer coefficient and effectiveness in the recovery region of a film-cooled surface

Mass transfer coefficients and film cooling effectiveness are measured downstream of a single row of holes (recovery region) inclined 30° with the surface and inline with the main turbulent boundary layer flow. The mass transfer coefficients are measured using a naphthalene sublimation technique. The effectiveness is determined through the injection of a trace gas into the secondary flow and measuring its concentration at the impermeable wall. Experiments are carried out in a subsonic, zero pressure gradient turbulent boundary layer, under isothermal conditions with three blowing ratios (U_j/U_∞): 0.4, 0.8, and 1.2. The data is collected in a region 7-80 jet diameters downstream of the injection location. From the data on mass transfer coefficients and effectiveness obtained under the same flow conditions a general mass transfer equation is derived. This paper presents extensive data and discussions; and is believed to be one of the few studies in which both of these variables are measured on the same surface and in a large area in the recovery region.