关键词: 纳米流体, 相变, 传热, CCD高速成像, 热力学过程, 传热模型

Abstract:

The CuO/H₂O nanofluids performance of the nucleate boiling heat transfer was analyzed. The copper oxide nanoparticles were synthesized by complexation precipitation process. Firstly, the precursors of copper oxide were prepared by mixing copper nitrate and salicylicacid with stir continuously around 30 min. Sodium carbonate were dropped slowly in the solution as precipitant until the Cu(Ⅱ) precipitated completely, then the precipitate was centrifugal washed for more than three times. Finally, the precipitate was calcined at 500℃ to obtain copper oxide nanoparticles. The copper oxide particles size was observed by the scanning electron microscope (SEM), and the sizes of particles are in the range of 40-80 nm. The CuO/H₂O nanofluid was prepared with the sodium dodecyl benzene sulfonate(SDBS) as the dispersant. The pool boiling heat transfer experiment was carried out to investigate the effect of thermal conductivity, contact angle and superficial particles deposition with different mass fractions on thermal performance of the nanofluid. The results have shown that the nanofluid can strengthen nucleate boiling heat transfer performance with CuO/H₂O nanofluid as working fluid. The heat transfer coefficient increased 146.1% than deionized water with the mass fraction of 0.1%. The bubble behavior of 0.07% nanofluid was recorded by the high-speed CCD to verify the boiling mechanism. Bubble dynamics model were built to predict bubble diameter, departure frequency and nucleation sites as the heat flux within 25 kW·m^-2 and 150 kW·m^-2. The absolute value of relative deviation between the numerical results and experimental results were less than ±10%.

Key words: nanofluid, phase change, heat transfer, visualization with CCD, thermodynamics process, heat transfer model