Mixed Convection in an Impinging Laminar Single Square Jet

摘要

The effect of Richardson number (Ri - Gr/Re~2= Ra/Pr Re~2) in a confined impinging laminar square jet was investigated numerically through the solution of Navier-Stokes and energy equations. The simulations were carried out for Richardson number between 0.05 and 8 and for jet Reynolds number between 50 and 300. The jet-to-target spacings were fixed to 0.25B, 0.5B, and LOB, respectively, where B is the jet width. The calculation results show that for the jet-to-target spacing of 0.25B, the flow structure of a square single jet impinging on a heated plate is not affected by the Richardson number. For such very small jet-to-target distances the jet is merely diverted in the transverse direction. The wall jet fills the whole gap between the plates with a very small vortex motion formed near the corners of the jet cross section close to the upper plate. In addition, the effect of the Richardson number on the variation in the local Nusselt number is found to be not significant. For higher jet-to-target spacing, the Nusselt number increased as the Richardson number increased for the same Re. In addition, the heat transfer rate increased as the jet Reynolds number increased for the same Richardson number.