Heat Transfer Enhancement of Impingement Cooling by Different Crossflow Diverters

Impingement cooling can effectively disperse local heat load, but its downstream heat transfer is always reduced due to crossflow effect. In this study, the flow and heat transfer characteristics of impingement cooling with Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS) crossflow diverters are compared over the ReD ranging from 3,500 to 14,000 by solving three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with SST k-? turbulence model. It is found that crossflow diverters change the distribution of local jet Reynolds number (ReD,j/ReD) and reduce the mass velocity ratio of downstream crossflow to jet (Gcf/Gj), so they enhance the heat transfer significantly, but also come at the cost of friction loss. Overall evaluation reveals that various crossflow diverters can improve the comprehensive heat transfer performance parameter (F), and the maximum increases are 11.0%, 14.3%, 12.2% and 14.7% for SC, SR, SD and SFS cases respectively. It is noted that the Nusselt number of heated SFS-shaped diverter surface is also the highest. Besides, the influences of streamwise location (L) and thickness (t) of SFS-shaped diverter are also investigated. Results show that the heat transfer and friction loss change a little when the L increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the L increases from 3D to 4D. With respect to the t, it has almost no effect on the flow field and heat transfer.