NSTI Nanotech 2009

Two-Phase Convective Heat Transfer in Microchannels

C-Y Lin, S-S Hsieh, J-H Chen
National Sun Yat-Sen University, TW

Keywords: microchannels, subcooling, convective boiling, CHF


Experiments were conducted to investigate subcooling flow boiling in 75 parallel microchannels (L=30 mm) having 200 μm (W) x 100 μm (H) cross-section with/without structured reentrant angle ( 0°、60°、90°and 120°). Boiling inceptions, flow morphologies, critical heat flux, heat transfer coefficients, and friction factor correlation were obtained for three different working mediums (DI water、DI water-MCNT(1 vol.%) nanofluids and FC-72) and two different heated surface material (Cu and Cu coated with 2 μm diamond film ) at G = 1500 kg/m2s and Tin = 23°C(see Fig.1). Results were compared to non- reentrant parallel microchannels ( 0°) at the same experimental conditions. It was found that the reentrant angle parallel microchannels can significantly decrease the wall superheat and increase the critical heat flux (CHF) (see Fig.2). Moreover, the working medium (DI water) with 1 vol.% nanoparticles and heated surface coated with 2 μm diamond film were also shown to significantly enhanced the heat transfer performance. The maximum CHF was found to be up to 602 W/cm2.
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