Flow and Heat Transfer Characteristics of an Impinging Jet in Crossflow at Low Nozzle-to-Plate Spacings

The research reported in this paper has measured in detail the near wall hydrodynamic and thermal characteristics of a confined single impinging jet in crossflow. To the authors’ knowledge, the work is unique in that the flow and thermal fields have been linked to the local surface heat transfer coefficients, which were measured at high resolution. The near wall velocity, turbulence, temperature and temperature fluctuation distributions of the jet were measured using hotwire anemometry and cold-wire thermometry. The target surface heat transfer coefficients were determined using the transient liquid crystal method. The multiple colour play coating enabled both the heat transfer coefficient and the adiabatic wall temperature distributions to be measured. The turbulent jet discharged with uniform exit velocity and temperature profiles at a Reynolds numbers of 20 000 and 40 000. The jet was subject to a crossflow at jet-to-crossflow velocity ratios of 1, 2, 3, 4 and 5. Two nozzle-to-plate spacings of 1.5d and 3d were examined. The results show that impinging jets in crossflow at z/d = 1.5 are significantly more intact at the target surface than jets with z/d = 3. As a result, the surface heat transfer rates beneath a jet in crossflow at the closer spacing are consistently higher. The results would provide excellent test cases for CFD works of similar flow configurations. The results are compared to related data in the literature. In addition, the driving gas temperature measured with the liquid crystals is compared to the near wall thermal field measured with the cold-wire.