Measurements of the convection heat transfer coefficient for a planar wall jet: uniform temperature and uniform heat flux boundary conditions

The local heat transfer coefficients for isothermal and uniform heat flux boundary conditions for a planar wall jet have been determined experimentally. Hot-wire anemometry surveys were used to quantify the velocity field in the wall jet. A micro-thermocouple was used to quantify the temperature field in the wall jet for the isothermal boundary condition. Infrared (IR) imaging was applied to measure the wall temperature for the uniform heat flux boundary condition. The difference in the local convection coefficients due to the different thermal boundary conditions was largest at the leading edge of the heated wall, becoming insignificant for non-dimensional streamwise locations exceeding approximately four slot widths away from the exit plane of the jet. The present results are for non-dimensional streamwise locations that are relevant to automotive windshield defogging/defrosting, which serves as the technological motivation for this study. Specifically, these results are for small non-dimensional streamwise locations compared to those in the published literature.