NUMERICAL INVESTIGATION OF VARIOUS APPROACHES TO AVOID NATURAL CONVECTION INSTABILITIES INSIDE THE CHANNELS OF HORIZONTAL PLATE FIN HEAT SINKS

In case of natural heat convection from a horizontal plate fin heat sink, heat transfer rates highly depend on the geometric parameters. It is observed that if the fin height is very low, fresh cooler air may not be able to reach middle parts of the heat sink causing an ineffective use of the extended heat transfer area. Using a validated numerical model of an underperforming heat sink, various ways of improving heat sink geometry has been investigated. The tried approaches include leaving gaps in the length of the fins in different patterns, adding two different shape pin fins in the channels between the plate fins and raising the height of the fins on the edges. The last approach is shown to be effective in improving heat transfer by blocking the side flows over the heat sink. By numerical simulations, causes of the unwanted in-channel longitudinal vortices were also investigated in detail with the help of powerful flow visualization capability of Computational Fluid Dynamics.