Measurements of Local Nusselt Number with a Miniscale Laminar Confined Slot-Jet Impinging on a Flat Plate

Heat transfer characteristics in a miniscale laminar confined slot-jet on a heated plate at uniform heat flux are experimentally investigated. The effects of the jet Reynolds number (Re = 120-180) on the heat transfer and flow are considered. An electrically heated gold film Intrex (a very thin gold-coated polyester substrate sheet) is used to create a uniform heat flux on the flat surface. The temperature on the surface is measured by thermochromic liquid crystals and a digital color image processing system. Recorded color images of liquid crystals are then used to determine the local Nusselt numbers along the surface. The results show a peculiar behavior in that the Nusselt number increases between Re = 120 and Re = 140, suddenly drops at around Re = 150-160, and increases again beyond Re = 160. This sudden drop of Nusselt number at around Re = 150-160 may be caused by a sinusoidal fluctuation of the jet flow.