关键词: 纳米粒子, 稳定性, 微通道, 红外热像仪, 传热

Abstract:

SiO₂, Al₂O₃ and TiO₂ nanofluids based on deionized water with a particle volume fraction of 0.1% were prepared by the two-step dispersion method. Surfactants were added into the nanofluids to reduce particle aggregation and enhance stability. An ultraviolet spectrophotometer was used to test the absorbance of nanofluids as the absorbance decreased with decreasing concentration of nanoparticles suspended in liquid. Based on the principle of transient plane source(TPS) method, the 2500 S thermal constant analyzer was employed to conduct the thermal conductivity of nanofluids. In order to investigate the heat transfer performance in a triangular microchannel heat sink using nanofluids, an Infrared Thermal Camera(ImageIR 3350, Germany) was inverted and hanged immediately over the microchannel heat sink to observe the temperature distribution on the substrate. The condition of heat dissipation was imitated by a DC power supply(34420A, Agilent, China), which would energize to the thin film heater at a heat flux of q=200 W·cm^-2. As different nanofluids were studied, DI-water was used to clean the experimental system after the previous experiment was done to avoid the residues of nanoparticles. The results reflected that the surfactants had effect on the absorbance of nanofluids, and the particles would aggregate with the increase of standing time. The thermal conductivity and convective heat transfer were improved by adding nanoparticles. The average temperature on substrate was cooled down, and the uniformity of temperature was also repaired. As the result, TiO₂ nanofluids had a better behavior than SiO₂ and Al₂O₃ nanofluids.

Key words: nanoparticles, stability, microchannels, thermal infrared imager, heat transfer