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Heat and Mass Transfer Enhancement by Carbon Nanotubes and Supersonically-Blown Nanofibers.

机译：碳纳米管和超音速吹胀纳米纤维增强了传热和传质。

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摘要

The present dissertation aims at the development and study of novel nanostructured materials useful for the enhancement of heat and mass transfer at macroscopic scales. For this two novel materials were used- supersonically-blown polymer nanofibers and phase change material encapsulated carbon nanotubes.;The supersonic solution blowing was developed to form nanofibers of the order of 50 nm from several polymers. The applicability of the process was first demonstrated with Nylon 6 and then was further introduced to different other polymers to produce 50 nm nanofiber on demand.;Supersonically-blown 50 nm Nylon 6 nanofibers were introduced to filtration applications, where such nanofibers were deposited on commercial filters to filter dangerous 100 nm nanoparticles from water. Ultrafine supersonically-blown nanofibers intercepted nanoparticles more than any other nanofibers. Such nanofibers intercept nanoparticles by means of the van der Waals forces and entrap them on the windward or leeward sides. A theoretical model was also developed to study nanoparticle-nanofiber interaction and the theoretical model accurately predicts nanoparticle collection on supersonically-blown nanofibers as seen experimentally.;The applicability of supersonically-blown ultrafine PAN nanofibers in thermal management applications was investigated next. A high-power surface mimicking a microelectronic a high-power substrate was coated with supersonically-blown PAN nanofibers. In one case they were metal-plated, whereas in another one pure polymer nanofibers were used. For both cases of metal-plated and non-metal plated nanofibers, it was observed that they facilitate nucleate boiling much more than bare Cu surface and lower surface superheat by several degrees at higher heat flux. Such texturing was also robust.;Thermal management of high-power microelectronics was also tackled in the present work using phase change materials (PCM) like wax and meso-erythritol encapsulated in carbon nanotubes. Such CNTs were used to form aqueous suspensions or suspensions in oil and used in through-flow in a microchannel embedded inside a high-power "microelectronics" block. Such nano-encapsulation dramatically shortened the PCM thermal response time and prevented sticking to the wall. With an increase in the CNT-PCM wt%, cooling via PCM melting became more and more pronounced.;Finally, a comprehensive quasi-one-dimensional model was developed for multiple polymer jets issued from a die nosepiece into a high-speed air flow and deposited onto a moving screen in solution blowing process. This study is fundamental for the ongoing studies of nanofiber formation in supersonic solution blowing.
机译：本论文旨在开发和研究新型的纳米结构材料，可用于在宏观尺度上增强传热和传质。为此，使用了两种新型材料：超音速吹塑聚合物纳米纤维和相变材料封装的碳纳米管。开发了超声波溶液吹塑法，可从几种聚合物中形成50 nm量级的纳米纤维。该方法的适用性首先在尼龙6上进行了证明，然后进一步引入到其他聚合物中，以按需生产50 nm纳米纤维。超音速吹制的50 nm尼龙6纳米纤维被引入到过滤应用中，这些纳米纤维被沉积在商业上过滤器可从水中过滤出危险的100 nm纳米颗粒。超细超音速吹胀的纳米纤维比其他任何纳米纤维都更能拦截纳米颗粒。这种纳米纤维通过范德华力拦截纳米颗粒，并将其截留在迎风侧或背风侧。建立了研究纳米粒子与纳米纤维相互作用的理论模型，并通过实验观察准确地预测了在超音速吹塑纳米纤维上的纳米粒子的收集情况;接下来研究了超音速吹塑超细PAN纳米纤维在热管理应用中的适用性。模仿微电子高功率基板的高功率表面涂有超声吹制的PAN纳米纤维。在一种情况下，它们是镀金属的，而在另一种情况下，则使用纯聚合物纳米纤维。对于金属镀覆和非金属镀覆的纳米纤维，都观察到它们在较高的热通量下比裸露的铜表面和较低的表面过热促进成核沸腾的程度要高得多。这种纹理化也很鲁棒。在当前的工作中，还使用相变材料（PCM）（如蜡和中碳赤藓醇封装在碳纳米管中）解决了高功率微电子的热管理问题。这样的CNT被用来形成水性悬浮液或在油中的悬浮液，并且被用于嵌入在高功率“微电子”模块内部的微通道中的流通中。这种纳米封装大大缩短了PCM的热响应时间，并防止了其粘附在墙上。随着CNT-PCM wt％的增加，通过PCM熔化的冷却变得越来越明显。最后，开发了一个全面的准一维模型，用于从模头连接到高速气流的多个聚合物射流然后在溶液吹制过程中沉积到移动的屏幕上。这项研究对于正在进行的超声速吹塑中纳米纤维形成的研究至关重要。

著录项

  • 作者

    Sinha Ray, Sumit.;

  • 作者单位

    University of Illinois at Chicago.;

  • 授予单位 University of Illinois at Chicago.;
  • 学科 Mechanical engineering.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 241 p.
  • 总页数 241
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 遥感技术;
  • 关键词

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