EAGER: Experimental Determination of Non-Evaporating Film Thickness in Pool Boiling

EAGER：池沸腾中非蒸发膜厚度的实验测定

• 批准号: 1445946
• 负责人: Shalabh Maroo
• 金额: $ 9.8万
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2016-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1445946&HistoricalAwards=false
• 关键词: EAGER; Experimental; Determination; Non; Evaporating

CBET-1445946MarooBoiling is used in domestic and industrial applications, ranging from residential refrigeration systems to power generation systems such as boiling water reactors. For example, about 90% of all electricity generation in the United States is by the use of steam turbines, where a large percentage of systems generate the steam using boilers. Due to its wide applicability, boiling has been researched for over five decades to understand bubble dynamics and attain enhancements in heat transfer; however, a complete knowledge of the bubble growth phenomenon is still lacking. One of the key missing pieces is the nanoscale non-evaporating liquid film (also known as the "adsorbed" film) widely theorized to exist at the base of a bubble. This film is of critical importance in bubble dynamics as it can sustain reduced/negative liquid pressure causing liquid to flow to the surface for evaporation and bubble growth. The non-evaporating film has not yet been directly measured in pool boiling experiments due to complexities associated with its nanoscale thickness and fluidic nature in the turbulent boiling process; the proposed research aims to overcome this shortcoming.The objective of the proposed research is to perform in-situ measurements of the nanoscale non-evaporating film thickness in pool boiling through the use of a novel interdisciplinary approach: application of two independent free-space optical techniques, spectral reflectometry and Michelson-interferometry, in pool boiling experiments of water. These high resolution techniques will enable measurement of the non-evaporating film thickness and its variation during a bubble's life-cycle in the isolated bubble regime at low heat fluxes. The effect of increasing heat flux and surface temperature on the film thickness will also be investigated. The experimental determination of the non-evaporating film thickness will facilitate accurate representation of the evaporation characteristics of the microlayer (region where the film is present) and its contribution to bubble growth, compared to current numerical simulations where the film is treated as a boundary condition with an assumed constant thickness. This work can also act as a basis for enhancing pool boiling heat transfer via novel surface modifications and other techniques aimed at altering the non-evaporating film and contact line region. The proposed research will enable new course materials and lab demonstrations to give students first-hand experience in interdisciplinary visualization techniques. Undergraduate students will also be actively engaged in the proposed research.

CBET-1445946 MarooBoiling用于家用和工业应用，从住宅制冷系统到沸水反应堆等发电系统。例如，美国约90%的发电量是使用蒸汽涡轮机，其中很大一部分系统使用锅炉产生蒸汽。由于其广泛的适用性，沸腾已经研究了五十多年，以了解气泡动力学并实现传热的增强;然而，仍然缺乏对气泡生长现象的完整了解。其中一个关键的缺失部分是纳米级的非蒸发液体膜（也称为“吸附”膜），理论上广泛存在于气泡的底部。该膜在气泡动力学中至关重要，因为它可以维持降低的/负的液体压力，从而导致液体流到表面进行蒸发和气泡生长。由于湍流沸腾过程中非蒸发膜的纳米级厚度和流体性质的复杂性，在池沸腾实验中还没有直接测量非蒸发膜的厚度;拟议的研究旨在克服这一缺点。拟议的研究的目的是通过使用一种新的跨学科方法来进行池沸腾中纳米级非蒸发膜厚度的原位测量：应用两个独立的自由空间光学技术，光谱反射法和迈克尔逊干涉法，在水池沸腾实验的水。这些高分辨率的技术将能够测量的非蒸发膜厚度和它的变化在气泡的生命周期中的孤立气泡制度在低的热通量。增加热通量和表面温度对薄膜厚度的影响也将被研究。非蒸发膜厚度的实验测定将有助于精确表示的微层（区域中的膜存在）的蒸发特性和它的贡献的气泡生长，相比，目前的数值模拟，其中的膜被视为一个边界条件与假设的恒定厚度。这项工作也可以作为基础，通过新的表面改性和其他技术，旨在改变非蒸发膜和接触线区域，以提高池沸腾传热。拟议的研究将使新的课程材料和实验室演示，让学生在跨学科的可视化技术的第一手经验。本科生也将积极参与拟议的研究。