Cylindrical porous inserts for enhancing the thermal and hydraulic performance of water-cooled cold plates

摘要

In the present study, a new class of porous inserts with the Rhombi-Octet unit cell design was proposed for enhancing the thermal and hydraulic performance of water-cooled cold plates with a cylindrical flow channel. Selective laser melting (SLM) was employed to fabricate the cold plates where the inserts were integrated to the flow channel walls in a single built piece. In all, three cold plates (P1, P2 and P3) with their flow channels fully filled with the porous structures of different unit cell sizes and three partially filled cold plates (API, AP2 and AP3) with porous structures of the same unit cell size but with different fill ratios (rho/P+s) were investigated. Their results were compared against the cold plates with empty flow channel and flow channel with helical inserts of different twist ratios (Y/D). The geometrical characteristics of the porous structures such as porosity (epsilon), strut length (l), width (w) and average pore diameter (d(ove)) were determined and their hydraulic performances were characterized using the Forchheimer-extended Darcy equation where the permeability (K) and inertia coefficient (C-E) of the respective porous structures were obtained. The cold plates with porous inserts show significant enhancements in the local (h(chi)) and length-averaged (h(ave)) heat transfer coefficients as compared to the cold plate with empty channel and helical inserts. In all, P1 exhibits h(chi) values as high as 18322 W/m(2).K and up to 383% enhancement in have as compared to the empty channel cold plate. On the other hand, the heat transfer coefficients also increase with increasing fill ratio, with AP3 exhibiting the highest (h) over bar (ave) amongst the cold plates with partially-filled porous inserts and surpassing those of the empty channel, helical insert and a fully-filled porous insert (P3) cold plate. At constant pumping power, Pl, P2, P3 and AP3 also show consistently lower average thermal resistances (R-ave) than all the other cold plates tested. (C) 2017 Elsevier Ltd. All rights reserved.