Subcooled flow boiling heat transfer of FC-72 from silicon chips fabricated with micro-pin-fins

Experiments were conducted to study the subcooled flow boiling heat transfer performance of FC-72 over silicon chips. For boiling heat transfer enhancement, two kinds of micro-pin-fins having fin thickness of 50 mu m and fin heights of 60 and 120 mu m, respectively, were fabricated on the silicon chip surface with the dry etching technique. The fin pitch was twice the fin thickness. The experiments were conducted at the fluid velocities of 0.5, 1 and 2 m/s and the liquid subcoolings of 15, 25 and 35 K. The micro-pin-finned surfaces showed a sharp increase in heat flux with increasing wall superheat and a large heat transfer enhancement compared to a smooth surface. The nucleate now boiling curves for the two micropin-finned surfaces collapsed to one line showing insensitivity to fluid velocity and subcooling, while the critical heat flux values increased with fluid velocity and subcooling. The micro-pin-finned surface with a larger fin height of 120 mu m provided a better flow boiling heat transfer performance and a maximum critical heat flux of 145 W/cm(2). The wall temperature at the critical heat flux for the micro-pin-finned surfaces was less than 85 degrees C for the reliable operation of LSI chips. (C) 2008 Elsevier Masson SAS. All rights reserved.