Two-phase flow and heat transfer in micro- and minichannels
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Two-phase flow patterns in micro- and minichannels
The need for reliable, high-performance, price-competitive electronic devices, most notably electronic chips, has created demand for comparably small heat transfer devices capable of removing the required heat load within a limited temperature range. Closed two-phase devices, such as miniature/micro heat pipes and capillary-pumped loops, have been and are being used successfully for this application. Typically, these use a spreading strategy and feature a large number of small circular channels arranged in parallel rows in a rectangular body.
See Main Article Two-phase flow patterns in micro- and minichannels
Flow condensation in micro- and minichannels
Condensation in miniature or micro channels finds its applications in electronics cooling, microscale energy, and Micro-Electro-Mechanical Systems (MEMS). The patterns of flow particularly relevant to a capillary tube include annular, slug, plug, and bubble (Tabatabai and Faghri, 2001). At the beginning of the two-phase flow, an annular layer forms on the inside of the tube. As vapor or gas velocity decreases, it causes ripples to form on the liquid surface, leading to the formation of collars. The collar can also result from condensation of the vapor on the liquid film in the tube.
See Main Article Flow condensation in micro- and minichannels
Flow evaporation and boiling in micro- and minichannels
The first onset of the vapor bubble marks the transition from the single-phase flow in the microchannel to two-phase flow, and for this reason, the prediction of onset of nucleate boiling (ONB) is very important.
See Main Article Flow evaporation and boiling in micro- and minichannels
References
Faghri, A., and Zhang, Y., 2006, Transport Phenomena in Multiphase Systems, Elsevier, Burlington, MA