Ultra-high heat flux boiling heat transfer of HFE-7100 in silicon-based distributed jet/pin-fin microchannel heat sinks

Abstract

The silicon-based hybrid distributed jet/inline pin-fin microchannel (JIPM) and distributed jet/staggered pin-fin microchannel (JSPM) heat sinks are proposed and constructed in this paper for ultra-high heat flux (>10³ W/cm²) chip-level cooling with dielectric fluid HFE-7100. By combined use of high-speed microscopic visualization and multi-parameter simultaneous measurement technology, the boiling heat transfer characteristics, pressure drop characteristics, and thermal-hydraulic performances of JIPM and JSPM heat sinks with jet velocities (u_j) of 0.86∼2.58 m/s and inlet subcoolings (ΔT_sub) of 21∼41 °C are experimentally investigated and compared with those of distributed jet/smooth microchannel (JSM) heat sink. The results show that compared with JSM: 1) both JIPM and JSPM can pre-trigger the onset of nucleate boiling (decreased the incipient wall superheats by up to 10.47 °C and 11.03 °C, respectively) due to the increase in nucleation sites; 2) critical heat fluxes for JIPM and JSPM are improved significantly (increased by 107 %∼140 % and 113 %∼149 %, respectively) because stable annular flow, which can prevent the local dry-out, is formed in these pin-fin microchannels. In particular, the JSPM heat sink can dissipate an ultra-high heat flux of 1041 W/cm² at a small pressure drop of 66.3 kPa when u_j = 2.58 m/s and ΔT_sub = 31 °C; 3) significant increases in heat transfer coefficient (HTC) (increased by 143 %∼159 % and 148 %∼169 %, respectively) and decreases in effective thermal resistance (decreased by 55.0 %∼59.2 % and 55.8 %∼60.5 %, respectively) are achieved for JIPM and JSPM because of their larger heat transfer areas and more nucleation sites. Moreover, JSPM has higher HTC and lower thermal resistance than JIPM due to the enhancement of fluid disturbance and prevention of bubble coalescence; 4) excellent base temperature uniformity and flow boiling stability are obtained for both JIPM and JSPM because the pin-fin structures in these microchannels help to enhance fluid disturbance, promote phase uniform distribution, and prevent reverse flow; 5) although the enhancement in heat transfer is at the cost of the increase in pressure drop, JIPM and JSPM have superior comprehensive thermal-hydraulic performances than JSM, with maximum COPs reaching 2967 and 2683, respectively.