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

摘要：

通过络合-沉淀法合成氧化铜纳米颗粒，制备铜颗粒的直径在40～100 nm，晶型为正六面体。利用“两步法”制备水基氧化铜纳米流体。考察了不同质量分数纳米流体的热导率、接触角变化和加热表面颗粒沉积对核沸腾传热性能的影响，并利用可视化记录沸腾过程气泡行为。结果表明：在测试质量分数范围内，传热系数随热通量增加而增大，当质量分数达到0.1%时，强化率最大为146.1%。经过分析可知纳米流体的接触角度、热导率、颗粒沉积以及颗粒扰动对水基氧化铜纳米流体强化传热作用均有影响。通过高速摄像采集质量分数0.07%纳米流体沸腾过程验证结论的可靠性。并对纳米流体核沸腾传热过程建立气泡动力学经验模型，模型计算结果与实测值相对偏差在±10%以内。

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