Flow boiling heat transfer coefficient of DI water and nanofluids inside microscale channels under conditions near the critical heat flux (CHF)

This study concerns an experimental evaluation of the heat transfer coefficient for saturated flow boiling of DI water and nanofluids under conditions close to the critical heat flux. Experimental data were gathered for DI-water-based nanofluids (composed of Al2O3 40-80 nm, Al2O3 10 nm, and SiO2 80 nm in volumetric concentrations up to 0.1%) and pure DI water in microscale channels (1.1 mm internal diameter) as received from the manufacturer and with the surface covered with a nanoporous layer resulting from the boiling process. Results were obtained for a saturation temperature of approximately 130 degrees C, mass velocities ranging from 133 to 494 kg/m(2)s, vapor qualities up to 0.9, and heat fluxes up to 2.5 MW/m(2). The DI-water experimental data on the bare surface were compared to prediction methods available in the literature. In general, the nanoporous layer characteristics play a major role in the effects of nanoparticles on the heat transfer coefficient.