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Rough surfaces with enhanced heat transfer for electronics cooling by direct metal laser sintering

Experimental evidences are reported on the potential of direct metal laser sintering (DMLS) in manufacturing flat and finned heat sinks with a remarkably enhanced convective heat transfer coefficient, taking advantage of artificial roughness in fully turbulent regime. To the best of our knowledge, this is the first study where artificial roughness by DMLS is investigated in terms of such thermal performances. On rough flat surfaces, we experience a peak of 73 % for the convective heat transfer enhancement (63 % on average) compared to smooth surfaces. On rough (single) finned surfaces, the best performance is found to be 40 % (35 % on average) compared to smooth finned surface. These results refer to setups with Reynolds numbers (based on heated edge) within 3,500 < Re_L < 16,500 (corresponding to 35,000 < Re_D < 165,000 in terms of Reynolds number based on hydraulic diameter). Experimental data are obtained by a purposely developed sensor with maximum and mean estimated tolerance intervals of +/- 7.0 % and +/- 5.4 %, respectively. Following the idea by Gioia et al. [Phys. Rev. Lett. 96 (2006) 044502], we propose that heat transfer close to the wall is dominated by eddies with size depending on the roughness dimensions and the viscous (Kolmogorov) length scale. An excellent agreement between the experimental data and the proposed analytical model is finally demonstrated.
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