Heat Transfer Enhancement of a Laminar Natural Convection Boundary Layer by Inserting Short Flat Plates Set in Array(Thermal Engineering)

An experimental study on heat transfer enhancement for a laminar natural convection boundary layer in air along a vertical flat plate has been performed by inserting short flat plates aligned in the spanwise direction with clearances (split heat transfer promoter) into the near-wall region of the boundary layer. Local heat transfer coefficients in the downstream region of the promoter substantially increase in comparison with those obtained for the usual laminar boundary layer without a promoter. Flow visualization shows that such remarkable heat transfer enhancement is attributed to longitudinal vortices generated by flows passing through the clearances of promoter in addition to vortex motions riding out the promoter. Consequently, it is concluded that the heat transfer enhancement can be achieved in the wide area of the laminar natural convection boundary layer by employing multiple-column split heat transfer promoters.