Evaporative Drying of Droplets and the Formation of Micro-structured and Functional Particles and Films

液滴的蒸发干燥以及微结构和功能颗粒和薄膜的形成

基本信息

批准号：
EP/N025245/1
负责人：
Colin Bain
金额：
$ 289.28万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2016
资助国家：
英国
起止时间：
2016 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FN025245%2F1
关键词：
Evaporative Drying Droplets Formation Micro

项目摘要

'Watching paint dry' is a metaphor for a boring and pointless activity. In reality, the drying of liquids is a complex process and the imperturbable appearance to the eye can hide a wealth of dynamics occurring inside the liquid. The effect of these internal processes is to change the distribution of materials in the deposit left after drying. We are all familiar with the coffee-ring effect, where split coffee dries to form a ring of solids at the edge of the spill - of little use if you are trying to coat a surface uniformly. This project is all about the drying of droplets, either in air or on a surface; one isolated droplet, two droplets merging or many droplets in a spray. We seek to understand how drops dry and how to control where the particles or molecules in the drop end up after the drop evaporates. When do you get a solid particle or a hollow particle? A round one or a spiky one? A uniform particle or one with shells? Or on a surface: a coffee-ring or a pancake? A uniform deposit, a layered one or a bull's eye? Are particles crystalline or amorphous, are different components mixed or separated? There are a myriad of possibilities for controlling the microstructure and properties of the final particle or film. Drying is complicated for three main reasons. First, many transport processes (evaporation, heat flow, diffusion, convection) occur simultaneously and are strongly coupled. For example, in a small droplet of alcohol and water evaporating on a surface, the liquid inside the drop will flow around in a doughnut pattern tens of times each second. Second, the conditions in a drying droplet are often far from equilibrium. For example, a small water droplet in air or on a smooth clean surface can be cooled to -35 degrees C without freezing. So to understand drying one needs to understand the properties of fluids far from equilibrium. It is generally not possible to predict the final outcome of drying from the properties of simple solutions near equilibrium. Third, drops do not dry in isolation. They may merge or bounce, coalesce or chase each other across a surface. The evaporation of one droplet affects its neighbours. Moving droplets change the flow of air around other droplets, coupling the motion of droplets.Why does anyone care, beyond the intellectual fascination with the bizarre outcomes of droplet drying? Drying of droplets turns out to be a rather important process in practical applications: spray painting, graphics printing, inkjet manufacturing, crop spraying, coating of seeds or tablets, spray cooling, spray drying (widely used in food, pharmaceutical and personal care products), drug inhalers and disinfection, to give a few examples. The physics and chemistry underlying all these applications is the same, but if manifests itself in different ways and the desired outcome varies between applications.The first challenge addressed by this project is one of measurement: how do you work out what is going on in a droplet that is less than a tenth of a millimetre across and may dry in less than a second? We have already developed sophisticated measurement tools but will need to extend these further. Another challenge is one of modelling: to understand the drying process we need a theoretical framework and computer models to explain - and predict - experimental observations. We will begin looking at the fundamental processes occurring in single drops in air and on a surface and then explore what happens when drops interact or coalesce. This fundamental understanding will be fed into improved models of arrays, clouds or sprays of droplets that are encountered in most practical applications (such as spray coating, spray drying, inhalers or inkjet manufacturing).We will use an Industry Club to engage with companies from a range of different sectors. This Club will provide a forum for sharing problems, ideas and solutions and for disseminating the knowledge generated in the project.

“看油漆干”是一个无聊和毫无意义的活动的隐喻。实际上，液体的干燥是一个复杂的过程，眼睛的外观不动摇可以隐藏液体内部发生的大量动态。这些内部过程的效果是改变干燥后剩余的沉积物中材料的分布。我们都熟悉咖啡环的效果，在那里，分裂的咖啡干燥以形成溢出边缘的固体环 - 如果您试图均匀地涂上表面，则很少使用。这个项目是关于在空气或表面上的液滴干燥。一个孤立的液滴，两个液滴合并或在喷雾中进行许多液滴。我们试图了解滴如何干燥以及如何控制滴液蒸发后滴剂中的颗粒或分子在哪里结束。您什么时候获得固体粒子或空心粒子？第一轮还是尖峰？一个均匀的粒子还是壳的粒子？还是在表面上：咖啡环还是煎饼？统一的沉积物，分层的或公牛的眼睛？颗粒是晶体或无定形的，不同的成分是否混合或分离？控制最终粒子或膜的微观结构和特性有无数的可能性。干燥复杂，原因有三个。首先，许多运输过程（蒸发，热流，扩散，对流）同时进行，并且强烈耦合。例如，在一小滴酒精和表面上蒸发的水中，液滴内部的液体将以甜甜圈的方式流动，每秒几十次。其次，干燥液滴中的条件通常远离平衡。例如，空气中或光滑的清洁表面上的小水滴可以冷却至-35摄氏度，而不会冷冻。因此，要了解干燥需要了解远离平衡的流体的特性。通常不可能从平衡附近的简单溶液的性质中预测干燥的最终结果。第三，滴不孤立地干燥。他们可以在表面上合并或弹跳，结合或互相追逐。一滴液滴的蒸发会影响其邻居。移动的液滴改变了其他液滴周围的空气流，将液滴的运动耦合在一起。为什么有人在乎，除了智力上的迷恋与液滴干燥的奇异结果外，是否在乎？在实用应用中，液滴的干燥是一个相当重要的过程：喷漆，图形打印，喷墨制造，作物喷涂，种子或片剂的涂层，喷雾冷却，喷涂干燥（广泛用于食品，药物和个人护理产品），药物吸入器和毒药和涂料，并提供了一些例子。所有这些应用所基于的物理和化学是相同的，但是如果以不同的方式表现出来，并且所需的结果在应用程序之间有所不同。该项目提出的第一个挑战是测量之一：您如何弄清楚液滴中发生的事情，而在跨度的第十毫米和少数毫米的十分之三？我们已经开发了复杂的测量工具，但需要进一步扩展这些工具。另一个挑战是建模之一：要了解干燥过程，我们需要一个理论框架和计算机模型来解释 - 并预测 - 实验观察。我们将开始研究空气中单滴和表面上发生的基本过程，然后探索滴相互作用或结合时会发生的情况。这种基本的理解将被馈入在大多数实用应用中遇到的阵列，云层或喷雾的改进模型（例如喷涂涂料，喷雾干燥，吸入器或喷墨制造）。我们将使用一个行业俱乐部与来自不同领域的公司互动。该俱乐部将提供一个论坛，用于共享问题，想法和解决方案，并传播项目中产生的知识。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Evaporation of a thin droplet in a shallow well: theory and experiment

DOI：
10.1017/jfm.2021.772
发表时间：
2021-10
期刊：
Journal of Fluid Mechanics
影响因子：
3.7
作者：
Hannah-May D'Ambrosio;Teresa Colosimo;B. Duffy;Stephen K. Wilson;Lisong Yang;C. Bain;Daniel E. Walker
通讯作者：
Hannah-May D'Ambrosio;Teresa Colosimo;B. Duffy;Stephen K. Wilson;Lisong Yang;C. Bain;Daniel E. Walker

Inertial stretching separation in binary droplet collisions

二元液滴碰撞中的惯性拉伸分离