Heat transfer experiments in a submerged impinging round jet using liquid crystal thermometry

Heat transfer measurements in a round submerged jet of air are presented for low nozzle-to-plate distances. A constant heat flux is imposed to the impingement wall and the heat transfer coefficient is determined from the resulting temperature field. The thermochromic liquid crystals are used for temperature measuremeents. The novelty of these measurements holds in the image-processing algorithm, which has been developed. The usual 1/2 power law dependence with the Reynolds number is verified in the laminar region for r/D < 0.6. Outside this region an exponent close to 2/3 is found. An interesting result of this work is the apparition, for low nozzle-to-plate spacing and sufficiently high Reynolds number, of non-axisymmetric modes of the plate temperature field which are probably a signature of Götler rolls. This phenomenon could be an analogy of appearance of vortical structures in the symmetry plane of planar impinging jets