EXPERIMENTAL STUDY ON AL_2O_3/H_2O NANOFLUID FLOW BOILING HEAT TRANSFER UNDER DIFFERENT PRESSURES

摘要

In present work, Al_2O_3/H_2O nanofluid was prepared by ultrasonic oscillation. Furthermore, nanofluid flow boiling heat transfer in a vertical cube is experimentally studied, with 0.1% and 0.5% volume concentration and 20nm diameter. Some factors are under consideration, including heat flux on the heating surface (48～289kW·m~(-2)), pressure (0.2～0.8MPa) and mass flow rate (400～1100 kgm~(-2)s~(-1)). The results confirm that the flow boiling heat transfer of Al_2O_3/H_2O nanofluid is improved mostly about 86% compared with pure water. And the average Nusselt number enhancement rate of nanofluid compared with deionized water is 35% in the range of this work. Moreover, the heat transfer capacity of nanofluid increase with the heat flux on the heating surface, pressure and the volume concentration of nanoparticle. It is proved that nanoparticle deposited on the heating surface by SEM observations, and TEM observations for nanoparticle confirm that nanoparticle have not obviously changed after boiling. In addition, the enhancement rate of nanofluid flow boiling heat transfer capacity increase with the pressure, and the influence of mass flow rate is negligible. In conclusion, this work is a supplement for nanofluid flow boiling heating transfer, especially for the influence of pressure.