Natural convection in a square cavity with two baffles on the vertical walls: Experimental and numerical investigation

Natural convection in a square enclosure filled with air is experimentally and numerically analyzed. The cavity has horizontal and vertical Plexiglas walls with discrete sources. Two Plexiglas baffles are attached to its vertical walls between the sources symmetrically. The effect of different baffle lengths is investigated. The results are presented for Rayleigh numbers from 104 to 10 5. The fluid flow field, thermal field and heat transfer are analyzed for two different baffle lengths through interferograms, streamlines, isotherms and velocity maps. The dimensionless baffle lengths investigated are L b= 0.2 and Lb= 0.4. The results clearly demonstrate that different baffle lengths have a significant effect on the heat transfer and flow characteristics of the fluid. The flow field pattern is baffle length and Rayleigh number dependent. It is, in fact, observed that for Lb= 0.2 the flow tends to circulate as a vortex strangled by the baffles, while for L b= 0.4 the flow tends to separate into two different vortices. The Nusselt number increases as Rayleigh number increases and it is a decreasing function of baffle length for the lower sources and increases for the higher sources. The average Nusselt numbers from Lb = 0.2 to Lb = 0.4 decrease on average by 23% on the lower source and it increases on average by 29% on the higher source.