Temperature Uniformity Enhancement and Flow Characteristics of Embedded Gradient Distribution Micro Pin Fin Arrays Using Dielectric Coolant for Direct Intra-Chip Cooling

Targeting at reducing temperature gradient in the direct intra-chip cooling, embedded gradient distribution micro pin fin arrays are fabricated. The flow characteristics and temperature uniformity performance are experimentally investigated using dielectric coolant (HFE7100). It is found the dependence of friction factor on Re is weak after reaching a critical Re (293) with a correlation of f similar to Re-0.14. Obvious flow fluctuations appear with steady stagnant symmetric vortices and unsymmetrical vortices by the experimentally validated numerical results, attributing to the abrupt rise of pressure drop. Moreover, the present gradient micro-pin fin arrays show great strengths in improving thermal performance and lowering temperature gradient. The thermal resistance and maximum temperature difference reduce by 34.6% and 8 K at the Q(v) of 100 ml/min and qw of 40 W/cm(2) compared to the uniform micro pin fin arrays for a same pumping power. Notably, the local temperature uniformity is also improved by gradient distribution micro pin fin arrays with absolute temperature deviations less than 2 K from x=1 mm to x=10 mm. The local Nu based on experimental data show a rapid increase (29%) in the second junction zone where unsteady wakes and flow acceleration occur, bringing considerable enhancement in mixing and local heat transfer. (C) 2020 Elsevier Ltd. All rights reserved.