NER: Nanofluid Characteristics in Pool Boiling

提案编号：CTS-0404174主要研究者： Ranganathan Kumar，Jayanta S. Kapat和Sudipta SealAffiliation： 中佛罗里达大学提案标题：NER：池沸腾中的纳米流体特性此提案是响应纳米科学与工程倡议，NSF 03-043，类别NER而收到的。最近发现纳米颗粒悬浮液可以增强流体的传热。相对于微米尺寸的悬浮液，纳米尺寸的悬浮液对静止流体中的沉降具有更大的抵抗力，当考虑微米尺寸的悬浮液时，这是一个重要的问题。此外，纳米流体的热导率随着纳米颗粒的尺寸减小而增加。有了这个额外的好处，值得探索纳米颗粒悬浮液在许多工程应用中作为潜在的冷却剂。纳米流体的传热特性明显更好，这增加了在灾难性故障之前提供给系统的功率能力。纳米流体还可以为现有的冷却系统提供潜在的回装，而无需在几个行业进行大修。由于这种潜力，需要研究对粒子运动的物理机制以及粒子如何影响临界热通量的基本理解。这项研究将侧重于量化和理解纳米流体的热导率大于预期的来源。作为本研究的一部分，将执行以下任务。 - 不同直径的二氧化铈和二氧化硅颗粒将在不同的温度下悬浮在水和其他流体中。 浓度，并将进行池沸腾实验。不同程度的CHF增强 将与相应的热导率测量一起测量。 - 对于每个实验，将测量颗粒在导线上的沉积。这些沉积 将使用SEM或TEM在不同浓度下对导线进行成像，以了解 nanofins对热传递的影响。 - 对于选定的实验，将使用荧光显微镜进行荧光成像， 纳米颗粒，并了解颗粒的偏好，团聚特性和 在不同温度下对材料的亲和力。由于二氧化硅颗粒不发荧光， 由于池沸腾中的沸腾特性与流动沸腾相似，纳米流体开辟了提高电子元件中的芯片功率、降低压水反应堆中的燃料元件表面温度以及降低冷却通道中的腐蚀速率的令人兴奋的可能性。该研究由化学和运输系统部门的热运输和热处理计划资助。

Proposal Number: CTS-0404174Principal Investigator: Ranganathan Kumar, Jayanta S. Kapat, and Sudipta SealAffiliation: University of Central FloridaProposal Title: NER: Nanofluid characteristics in Pool BoilingThis proposal was received in response to Nanoscale Science and Engineering initiative, NSF 03-043, category NER. Nanoparticle suspensions have recently been discovered to enhance the heat transfer of fluids. Relative to micron-sized suspensions, the nano-sized suspensions are much more resistant to settling in stationary fluids, which is a significant concern when micron-sized suspensions are considered. In addition, the thermal conductivity of the nanofluid increases as the size of the nanoparticles decreases. With this added benefit, it is worth exploring nanoparticle suspension as potential coolants in a number of engineering applications. The heat transfer characteristics are significantly better in a nanofluid, which increases the power capability provided to a system prior to catastrophic failure. Nanofluids may also offer a potential back fit to existing cooling systems without a major overhaul in several industries. Because of this potential, fundamental understanding of the physical mechanisms in particle motion and how the particles affect the critical heat flux need to be studied. This research will focus on quantifying and understanding the source of the greater than expected thermal conductivity of nanofluids. As part of this study, the following tasks will be performed. - Different diameter ceria and silica particles will be suspended in water and other fluids at different concentrations, and pool-boiling experiments will be done. Different levels of enhancement of CHF will be measured with corresponding measurements of thermal conductivity. - For each experiment, the deposition of the particles on the wire will be measured. These deposited wires will be imaged using an SEM or TEM at different concentrations to understand the role of nanofins on the heat transfer. - For selected experiments, fluorescence imaging will be done using a fluorescence microscope to track the nanoparticles and to understand the particle preference, agglomeration characteristics and affinity to materials at different temperature. Since the silica particles do not fluoresce, quantum dots will be used to dope silica for imaging at least in one experiment for a specific diameter.Since the boiling characteristics in pool boiling is similar to flow boiling, nanofluids have opened up exciting possibilities of raising chip power in electronic components, reducing fuel element surface temperature in pressurized water reactors, and reducing corrosion rates in cooling channels. The research is being funded by the Thermal Transport and Thermal Processing Program of the Chemical and Transport Systems Division.