Flow boiling characteristics in bi-porous minichannel heat sink sintered with copper woven tape

Micro/minichannel heat sinks with functional structure surface provide a potential solution for the thermal management of increasing heat flux electronic devices. In this study, a novel bi-porous minichannel heat sink (BPM) sintered with copper woven tape is proposed to enhance the flow boiling heat transfer performance. On the surface of the copper woven tape there are two kinds of pore structures, comprising cavities formed by copper strands and crevices formed by copper wires. The flow boiling performances, including heat transfer performance, pressure drop and flow instability at different mass fluxes of G=158, 253, 348 kg/m(2).s, were experimentally investigated for BPM. Besides, a comparison study with a conventional rectangular minichannel with plain surface (PSM) was also conducted. The bubble behaviors observed by high-speed camera were investigated and analyzed. It is found that the onset of nucleate boiling of BPM is triggered at smaller wall superheat than that of PSM, benefiting from the larger quantity and more uniform distribution of nucleation sites generated by the novel bi-porous structure. The heat transfer coefficient of BPM is larger than that of PSM whether at low or high heat flux. Due to the uneven surface of the copper woven tape, the pressure drop of BPM increases more significantly with increasing heat flux, and is notably dependent on the mass flux and vapor quality. The flow instability is more moderate at a given mass flux owing to the more uniform bubble size and bubble distribution. This study shows that BPM is of high heat transfer performance and offers relatively stable operation condition, which is promising to solve thermal problem for high heat flux application. (C) 2020 Elsevier Ltd. All rights reserved.