posted on 2020-10-05, 21:09authored byWenming Li, Yogendra Joshi
To
enable rapid development of flexible microelectronic systems,
effective thermal management is needed. Flexible polydimethylsiloxane
(PDMS)-based microchannel flow boiling may provide a desirable solution.
However, the heat transfer performance of PDMS-based microchannels
is diminished by its poor thermophysical properties. The development
of PDMS wick is proposed to address this dilemma. Herein, a new PDMS
wick structure is designed and integrated in the microfluidic device
to significantly enhance its thermal performance by promoting capillary-driven
flow. Furthermore, to achieve highly efficient vapor removal, a dedicated
vapor pathway is designed in the microfluidic device. Experiments
have been conducted to investigate the capillary-assisted evaporation/boiling
for mass flux ranging from 70 to 245 kg/m2 s on dielectric
fluid HFE-7100. The capillary-assisted sustainable and stable thin
film evaporation and efficient vapor removal have been demonstrated
through the visualization studies. With this new wick design, the
liquid rewetting at global and local levels is facilitated through
the capillary-driven flow and the efficient vapor removal. This hybrid
liquid rewetting mechanism is experimentally demonstrated to significantly
enhance the capillary-assisted evaporation/boiling in PDMS-based microchannel.
A critical heat flux (CHF) of 14.7 W/cm2 is achieved at
a mass flux of 245 kg/m2 s. The heat transfer coefficients
(HTC) range from 2000 to 9800 W/m2 K. These values are
comparable to that in copper/silicon microchannels, with the aforementioned
benefits of flexibility. Equally importantly, stable two-phase transport
is achieved as well.