纳米流体静电雾化特性的实验研究

发布时间：2018-08-03 07:44

【摘要】：随着电子产品的发展,芯片集成化程度越来越高,在微米级尺度上对芯片进行散热是极具挑战性的课题。高效导热薄膜材料为芯片散热问题的解决提供了新思路。近年来,采用纳米流体的静电雾化沉积制备高效导热薄膜材料逐渐引起了国内外学者的关注。纳米流体因其自身物理性质的特异性,其静电雾化特性区别于普通流体,深入了解纳米流体静电雾化特性并探索其破碎机制可为发展高效薄膜制备技术奠定理论基础。基于此,本文对纳米流体的静电雾化特性进行了基础性的实验研究,主要工作如下:采用显微高速数码摄像技术对纳米流体的静电雾化模式转变进行了可视化研究。以不同组份的纳米流体为研究介质,精确捕捉了不同工况下纳米流体雾化形态的演变行为;探索了质量分数及流量等因素对纳米流体雾化模式转变的影响。实验结果表明:随着质量分数的升高,纳米流体的锥射流模式区间逐渐缩小,过渡到锥射流状态的临界电场强度逐渐增大,而电导率的升高使得纳米流体更易过渡到多股射流模式。流量的增加削弱了雾化的稳定性,形成锥射流及多股射流所需的电场强度越高。绘制了电场强度和流量影响下特定组份纳米流体的雾化模式图,为探索和发展薄膜材料的制备技术奠定了基础。基于纳米流体静电雾化模式的转变规律,对各雾化模式下的液滴沉积分布特性进行了实验研究。实验结果表明:随着电压的增大,液滴粒径呈减小趋势,滴状模式下液滴粒径呈指数减小;锥射流模式下液滴粒径呈线性减小;多股射流模式下液滴粒径变化较为复杂。流量的降低可使液滴粒径有所减小,但液滴粒径减小并不明显;流量降低后,液滴粒径分布较宽,小粒径液滴所占比例有所升高。对不同组份纳米流体荷电液滴在气动作用下的变形破碎特性进行了实验研究。结果表明:荷电液滴袋状破碎过程;中随着纳米颗粒质量分数的增加,荷电液滴袋的生长及袋的破碎所需时间逐渐减少;高荷电量的乙醇液滴与低荷电量的石墨-乙醇纳米流体液滴在破碎过程中,破碎所需时间以及形态都极其类似,这表明纳米颗粒的加入促进了气动作用下荷电液滴袋状破碎的进程。
[Abstract]:With the development of electronic products, the integration of chips is becoming more and more high. High-efficiency thermal conductive thin-film materials provide a new way to solve the problem of chip heat dissipation. In recent years, the preparation of high efficiency thermal conductivity thin films by electrostatic atomization deposition of nanofluids has gradually attracted the attention of scholars at home and abroad. The electrostatic atomization property of nano-fluid is different from that of ordinary fluid because of its own specific physical properties. Understanding the electrostatic atomization characteristics of nano-fluid and exploring its crusher can lay a theoretical foundation for the development of high-efficiency thin film preparation technology. Based on this, the basic experimental study of electrostatic atomization characteristics of nano-fluid is carried out in this paper. The main work is as follows: the visualization study of electrostatic atomization mode transformation of nano-fluid is carried out by using micro-high-speed digital camera technology. The evolution behavior of nano-fluid atomization morphology under different working conditions was accurately captured with different components of nano-fluid as the research medium, and the effects of mass fraction and flow rate on the transformation of nano-fluid atomization mode were explored. The experimental results show that with the increase of mass fraction, the range of conical jet mode of nano-fluid gradually decreases, and the critical electric field intensity of transition to cone-jet state increases gradually. The increase of conductivity makes it easier for nanoscale fluid to transition to multi-strand jet mode. With the increase of flow rate, the stability of atomization is weakened, and the electric field intensity required for the formation of conical jet and multi-jet is higher. The atomization mode diagram of nano-fluids with specific components under the influence of electric field intensity and flow rate was drawn, which laid a foundation for exploring and developing the preparation technology of thin film materials. Based on the transformation rule of electrostatic atomization mode of nano-fluid, the deposition distribution characteristics of droplets in different atomization modes were studied experimentally. The experimental results show that the droplet size decreases with the increase of voltage, decreases exponentially in droplet mode, linearly decreases in cone-jet mode, and complex in multi-strand jet mode. When the flow rate decreases, the droplet size decreases, but the droplet size decreases not obviously. After the flow rate decreases, the droplet size distribution is wider, and the ratio of small droplet size increases. The characteristics of deformation and breakage of charged droplets with different components under aerodynamic action were investigated experimentally. The results show that the growth of charged droplet bags and the time required to break them decrease with the increase of the mass fraction of nanoparticles. The breakage time and morphology of high-charge ethanol droplets and low-charge graphite-ethanol nano-fluid droplets are very similar. This indicates that the addition of nanoparticles promotes the process of charged droplet bag breakage under pneumatic action.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.1

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