J.M. Wu

Experimental study on Al2O3/H2O nanofluid flow boiling heat transfer under different pressures

In present work, Al2O3/H2O 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−2s−1). The results confirm that the flow boiling heat transfer of Al2O3/H2O 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.Copyright

Conjugated Numerical Study on the Performance of Microchannel Heat Sink Using Al2O3/H2O Nanofluid

High power electronics are widely used in many different areas such as integrated circuit (IC) boards in nuclear reactor control system. Thermal management of electronic devices has been a topic of great interest among many researchers over the last few decades. Microchannel is one of several high-heat-flux removal techniques. Nanofluids with enhanced thermal conductivity and strong temperature- and size-dependent thermal properties are expected to be utilized in microchannels as coolants, which leads to a promising future for such high-heat-flux systems as cooling systems. The performance of the microchannel heat sink (MCHS) using water and Al2O3/water nanofluids, with consideration of different substrate materials, is numerically investigated and compared in the present paper to identify the combined effects of working fluids and substrate materials on the thermal resistance, pumping power and temperature distribution on the substrate surface of a heat sink.Copyright

Nanofluid Boiling Heat Transfer and Critical Heat Flux Enhancement: Mechanism to Be Revealed

As a novel strategy to improve heat transfer characteristics of fluids by the addition of solid particles with diameters below 100 nm, nanofluids exhibits unprecedented heat transfer properties and are being considered as potential working fluids to be used in high heat flux systems such as nuclear reactors, electronic cooling systems and solar collectors. The present paper reviews the state-of-the-art studies on nanofluid boiling heat transfer performance and critical heat flux (CHF) enhancement. It is found that some results on nanofluids boiling heat transfer performance are inconsistent or contradictory in data published. The knowledge on the mechanism of nanofluids boiling CHF enhancement is insufficient. Bubble dynamics of nanofluids boiling is suggested to be investigated to identify the exact contributions of solid surface modifications and suspended nanoparticles to CHF enhancement in nanofluids boiling heat transfer.Copyright