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 Re_D ranging from 3,500 to 14,000 by solving three dimensional Reynolds-averaged Navier–Stokes equations with SST k–ω turbulence model. It is found that the arrangement of crossflow diverters changes the distribution of local jet Reynolds number (Re_D,j/Re_D) and reduces the mass velocity ratio of downstream crossflow to jet (G_cf/G_j), so the impingement heat transfer is enhanced significantly. However, friction loss also increases. Overall evaluation reveals that all crossflow diverters can improve the comprehensive heat transfer performance parameter (Φ), and the maximum increases of Φ 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 when the L increases from 2D to 3D, the heat transfer and friction loss change slightly; when the L increases from 3D to 4D, the heat transfer decreases sharply, and friction loss increases seriously. As for the t, it has almost no effect on the flow field and heat transfer.