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Faculty of Mechanical Engineering, Lj. (FSLJ)
  • Nucleation cavities effect on the onset of nucleate boiling in microchannels [Elektronski vir]
    Sitar, Anže ; Zupančič, Matevž, 1990- ; Golobič, Iztok
    The cooling systems of various computer components present the bottleneck of the future development of more powerful chips which progress according to the Mooreʼs law , as the widely used forced ... convection air cooled heat sinks are already at the limit of their cooling capacity. Therefore, further improvements of electronic components depend heavily on the next generation of cooling technologies with lower thermal resistances. One of the prominent possibilities is the employment of flow boiling and microchannels to enhance the cooling capabilities of heat sinks. However, the boiling phenomenon introduces a unique set of challenges, which must be surpassed to enable the use of the two-phase flow advantages. Microchannels have a large area to volume ratio, which is the origin of the improved heat transfer coefficient, as the heat transfer occurs mostly at the solid/fluid interface. One of the major drawbacks of the microchannels is that the small hydraulic diameter along with the smooth channel walls inhibits the onset of nucleate boiling (ONB) at low excess temperatures. The presented paper is addressing this issue with the fabrication of potential nucleation cavities in the microchannel walls and bottom, which lower the temperature of the ONB. Moreover, inlet flow restrictors were incorporated to reduce the boiling instabilities and hinder vapor backflows. Experiments were conducted with double distilled degassed water in arrays of microchannels with the hydraulic diameter ranging from 25 to 80 [micro]m, whereas the nucleation cavities sizes varied from 2 to 12 [micro]m. The experimental results demonstrate the effect of microchannel size, surface roughness and nucleation cavity size on the temperature of the ONB. The measured temperatures and the determined heat transfer coefficient clearly show the importance of the active nucleation cavities. The temperatures of the ONB were up to 35 K lower and the heat transfer coefficient up to ten times higher in the microchannel array with nearly optimal nucleation cavities compared to the other arrays of microchannels, in which the etched nucleation cavities were not properly sized.
    Source: MIT 2014 [Elektronski vir] : proceedings of the 13th International Conference on Management of Innovative Technologies, Fiesa, Slovenia, 28th - 30th September 2014 (F. 95-104)
    Type of material - conference contribution
    Publish date - 2014
    Language - english
    COBISS.SI-ID - 13895963

    Link(s):

    https://mitconference.files.wordpress.com/2014/12/mit2014-conference-proceedings.pdf

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