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

基本信息

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

项目摘要

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-1445946MarooBoiling 用于家庭和工业应用，范围从住宅制冷系统到发电系统（例如沸水反应堆）。例如，美国约 90% 的发电是通过蒸汽轮机实现的，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，沸腾已经被研究了五十多年，以了解气泡动力学并增强传热；然而，人们仍然缺乏对泡沫增长现象的完整了解。关键缺失部分之一是纳米级非蒸发液膜（也称为“吸附”膜），广泛认为存在于气泡底部。该薄膜在气泡动力学中至关重要，因为它可以维持降低/负的液体压力，导致液体流到表面进行蒸发和气泡生长。由于其纳米级厚度和湍流沸腾过程中的流体性质相关的复杂性，非蒸发膜尚未在池沸腾实验中直接测量；本研究旨在克服这一缺点。本研究的目的是通过使用一种新颖的跨学科方法对池沸腾中的纳米级非蒸发膜厚度进行原位测量：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，用于水池沸腾实验。这些高分辨率技术将能够测量非蒸发膜厚度及其在低热通量下孤立气泡状态下气泡生命周期中的变化。还将研究增加热通量和表面温度对薄膜厚度的影响。与当前将薄膜视为边界条件的数值模拟相比，非蒸发薄膜厚度的实验确定将有助于准确表示微层（薄膜所在区域）的蒸发特性及其对气泡生长的贡献假设厚度恒定。这项工作还可以作为通过新颖的表面改性和旨在改变非蒸发膜和接触线区域的其他技术来增强池沸腾传热的基础。拟议的研究将启用新的课程材料和实验室演示，为学生提供跨学科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。