NER: Nanofluid Characteristics in Pool Boiling

项目编号：csts -0404174首席研究员：Ranganathan Kumar， Jayanta S. Kapat和Sudipta seal隶属于中佛罗里达大学。项目名称：NER：池沸水中的纳米流体特性。该提案是响应纳米尺度科学与工程计划，NSF 03-043， NER类别。纳米颗粒悬浮液最近被发现可以增强流体的传热。相对于微米级的悬浮液，纳米级的悬浮液在静止流体中的抗沉降性要强得多，这是考虑微米级悬浮液时需要考虑的一个重要问题。此外，纳米流体的热导率随着纳米颗粒尺寸的减小而增加。有了这个额外的好处，纳米颗粒悬浮液在许多工程应用中作为潜在的冷却剂是值得探索的。纳米流体中的传热特性明显更好，这增加了在灾难性故障之前为系统提供的功率能力。纳米流体还可以为一些行业的现有冷却系统提供潜在的回配，而无需进行大检修。由于这种潜力，对粒子运动的物理机制和粒子如何影响临界热流的基本理解需要研究。本研究将集中于量化和理解纳米流体大于预期导热系数的来源。作为本研究的一部分，将执行以下任务。-在不同浓度的水和其他流体中悬浮不同直径的二氧化铈和二氧化硅颗粒，进行池沸实验。不同程度的CHF增强将通过相应的热导率测量来测量。-对于每个实验，将测量金属丝上颗粒的沉积情况。将使用不同浓度的扫描电镜或透射电镜对这些沉积的金属丝进行成像，以了解纳米鳍在传热中的作用。-对于选定的实验，将使用荧光显微镜进行荧光成像，以跟踪纳米颗粒，并了解颗粒在不同温度下的偏好，团聚特征和对材料的亲和力。由于二氧化硅颗粒不发出荧光，量子点将被用于掺杂二氧化硅成像，至少在一个特定直径的实验中。由于池沸腾中的沸腾特性与流动沸腾相似，纳米流体为提高电子元件的芯片功率、降低压水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开辟了令人兴奋的可能性。该研究由化学和运输系统分部的热传输和热处理项目资助。

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.