Critical Heat Flux (CHF) of Subcooled Flow Boiling of Alumina Nanofluids in a Horizontal Microchannel

This work investigates subcooled flow boiling of aqueous based alumina nanofluids in 510 μm single microchannels with a focus on the effect of nanoparticles on the critical heat flux. The surface temperature distribution along the pipe, the inlet and outlet pressures and temperatures are measured simultaneously for different concentrations of alumina nanofluids and de-ionized water. To minimize the effect of nanoparticle depositions, all nanofluid experiments are performed on fresh microchannels. The experiment shows an increase of ∼51% in the critical heat flux under very low nanoparticle concentrations (0.1 vol %). Different burnout characteristics are observed between water and nanofluids, as well as different pressure and temperature fluctuations and flow pattern development during the stable boiling period. Detailed observations of the boiling surface show that nanoparticle deposition and a subsequent modification of the boiling surface are common features associated with nanofluids, which should be responsible for the different boiling behaviors of nanofluids.