Critical Heat Flux During Subcooled Flow Boiling of Alumina Nanofluids in a Narrow Channel

This work reported an experimental study of flow boiling of pure water and aqueous alumina nanofluids in a 0.5 millimetre narrow channel. An open-ended stainless steel microchannel system is constructed where liquids are supplied by a syringe pump and heated by a variable DC power source, with synchronized measurement of the surface temperature distribution along the channel and pressure fluctuations associated with bubbles. The effect of nanoparticle concentration, inlet subcooling and mass flow rate and on critical heat flux in a microchannel is investigated. A modest increase in CHF is observed for nanofluids, being higher at higher particle concentrations and higher inlet subcoolings. Regular fluctuations in temperature and pressure signals suggest a cyclic boiling events occurring in the narrow channel; the large pressure fluctuation, coupling with the surface temperature and inlet temperature fluctuations, would affect flow boiling mechanisms in narrow channels.