Impingement transfer coefficients due to initially laminar slot jets

The transfer coefficients resulting from the impingement of a slot jet on a plane surface have been measured by the naphthalene sublimation technique. The experiments were performed with jets that are laminar at the exit of the duct from which the jet issues. In addition, the velocity profiles at the duct exit were fully developed. Distributions of the local mass-transfer coefficient on the impingement surface were determined for five Reynolds numbers and at five separation distances between the duct and the surface. The mass-transfer results can be converted to heat-transfer results by using the heat-mass transfer analogy. It was found that the transfer coefficients generally tended to decrease with increasing separation distance, but there was evidence of non-monotonic behavior owing to the opposite influences of mixing-induced turbulence and diminished jet velocity. Increases in Reynolds number tended to increase the transfer coefficients, and the stagnation point values were correlated with a 0·6-power dependence. The surface distributions of the transfer coefficient were bell-shaped, with the largest value at the stagnation point. Comparisons with available literature suggested that the shape of the initial velocity profile has a significant effect on the transfer characteristics of the impingement surface.