Hydrodynamic and thermal analysis of a micro-pin fin evaporator for on-chip two-phase cooling of high density power micro-electronics

The global tendency towards miniaturization driven by the micro-electronics industry is pushing system density and packaging towards unprecedented values of thermal design power, with a dramatic reduction of the surface area of the devices.As such, the thermal management of these systems requires novel and smarter cooling methods, in particular in view of the next generation of 3D integrated circuits.On-chip two-phase cooling represents a very attractive long-term solution to this problem.Two-phase flow boiling in a micro-pin fin heat sink is experimentally studied here for this cooling process.The micro evaporator tested has a heated area of 1 cm(2), consisting of 66 rows of cylindrical in-line micro-pin fins with a diameter, height and pitch of respectively 50 mu m, 100 mu m and 91.7 mu m.An infrared temperature measurement technique is coupled with high-speed flow visualization to investigate the fluid dynamics and heat transfer associated with flow boiling in the micro-evaporator.Time-dependent features of the flow, operational maps, pressure drop and heat transfer performance in stable flow conditions under a range of heat flux and mass flux of, respectively, 20-44W cm(-2) and 750-1750 kg m(-2) s(-1), and a constant outlet saturation temperature of 25 degrees C, are experimentally investigated.The fluid used is the dielectric refrigerant R134a.This study shows that R134a exhibits a very stable flow boiling behavior under a wide range of flow conditions.Low amplitude temperature oscillations with frequencies in the range of 14-22 Hz are detected and the high-speed videos demonstrate that these are related to the bubble nucleation process.The heat transfer coefficient trends along the test section are strongly dependent on the vapor quality, with local values as high as50 kW m(-2) K-1 measured in the proximity of the flow area exit. This dependency is attributed to the impact of the two-phase flow patterns which develop along the channels, i.e. slug and annular flow. The heat transfer performance enhances significantly with the applied heat, while mass flux exhibits a minor influence. (C) 2017 Elsevier Ltd. All rights reserved.