Evaporation enhancement for evaporative cooling systems

蒸发冷却系统的蒸发强化

• 批准号: RGPIN-2014-04197
• 负责人: MacDonald, Brendan
• 金额: $ 1.68万
• 依托单位: University of Ontario Institute of Technology
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566360
• 关键词: Evaporation; enhancement; evaporative; cooling; systems

Cooling is of critical importance for a wide range of fields. Presently, there are two fields where cooling is essential for realizing performance and growth potential: (1) microelectronic devices, which have components that are continually decreasing in size while facing an increase in power demands and corresponding need for heat removal, and (2) air conditioning for residential and commercial spaces, which is correlated with productivity and energy demand. There are relatively limited methods for cooling, most of which require refrigerants that can damage the environment. Current technology is not keeping pace with the rising cooling demands so there is a need for efficient and environmentally friendly technology. We take our inspiration for efficient cooling from nature, where human perspiration serves as an example of using evaporating droplets for cooling. Evaporation can provide very efficient cooling by exploiting the large amount of energy dissipated during a liquid to vapour phase change. Sessile droplets offer advantages over film and pool boiling due to their high surface area to volume ratios, which are beneficial for interfacial processes such as evaporation. There is great potential for evaporative cooling technology using sessile droplets; however, there is still an inadequate understanding of the evaporation process and the role of interfacial effects. Better understanding of the influence of interfacial effects on evaporation will lead to improved performance and efficiency, which is especially crucial as technology decreases in size to the micro- and nano-scales where interfacial effects become more important. This research program investigates an interfacial effect known as Marangoni convection, which is caused by an imbalance of surface tension forces at a liquid-vapour interface, and results in fluid flow within a droplet. In certain circumstances Marangoni convection has been shown to substantially increase evaporation rates and a majority of the energy required for evaporation is transported by Marangoni convection along the surface of a droplet. The enhanced evaporation rates can be used to improve cooling technology performance; however, this behaviour is still poorly understood and fluctuates based on the properties of the droplet (size, chemical mixture) and the substrate material. The objectives of this research are to: (1) quantify the influence of Marangoni convection on evaporation rates using experimental techniques for various sessile droplet sizes, fluid mixtures, and substrate materials, (2) develop and validate mathematical and numerical models of the evaporation process, which include the effects of Marangoni convection as a method for increasing the evaporation rates, and (3) apply the findings to develop energy efficient evaporative cooling technology by generating designs and performing simulations with our models. This research program aims to develop energy efficient, high capacity, and environmentally friendly evaporative cooling technology. Cooling living and working spaces using current technology places high demands on energy requirements, particularly in developing countries, but also in warm and humid Canadian summers. Cooling in electronic devices presents an opportunity for new technology to enter the market since power density and performance are limited by the overheating of components. We will generate an understanding and quantification of the influence of Marangoni convection on evaporation rates in sessile droplets, which will be valuable for a broad range of applications. This research will produce highly qualified personnel who are proficient in the thermal management and energy fields, which are significant for many expanding Canadian industries.

对于广泛的领域，冷却至关重要。目前，在两个领域中，冷却对于实现性能和增长潜力至关重要：（1）微电子设备的尺寸不断降低，同时面对功率需求的增加和相应的去除排放需求，以及（2）住宅和商业空间的空气措施，这些空间与生产力和能源需求相吻合。冷却的方法相对有限，其中大多数需要制冷剂才能破坏环境。当前的技术并没有跟上不断增长的冷却需求，因此需要有效且环保的技术。我们从大自然中汲取灵感来有效冷却，在这种情况下，人类的汗水是使用蒸发液滴进行冷却的一个例子。蒸发可以通过利用在液体中耗散的大量能量来变化来提供非常有效的冷却。连因为液滴的表面积高与体积比，因此无板液滴具有比薄膜和池沸腾的优点，这对诸如蒸发等界面过程有益。使用无柄液滴的蒸发冷却技术具有很大的潜力。但是，仍然对蒸发过程和界面作用的作用仍然不足。更好地理解界面影响对蒸发的影响将提高性能和效率，这对于微观和纳米级的尺寸降低了，在界面效应变得更加重要，这一点尤为重要。该研究计划研究了一种称为Marangoni对流的界面效应，该效应是由液态蒸气界面处的表面张力不平衡引起的，并导致液滴内的流体流动。在某些情况下，Marangoni对流已显示出大幅提高蒸发率，并且蒸发所需的大部分能量是通过Marangoni对流沿液滴表面传输的。增强的蒸发率可用于提高冷却技术性能；然而，这种行为仍然很少理解，并且根据液滴（尺寸，化学混合物）和底物材料的特性而波动。这项研究的目的是：（1）使用实验技术来量化Marangoni对流对蒸发率的影响，用于各种无柄液滴尺寸，流体混合物和底物材料，（2）开发和验证蒸发过程的数学和数值模型，包括为MARANGONI的效果而提高Marangoni的效果，以实现Marangoni的效果，并（3）（3）（3）（3通过使用我们的模型来生成设计和执行模拟来冷却技术。该研究计划旨在开发节能，高容量和环保蒸发冷却技术。使用当前技术的冷却生活和工作空间对能源需求，特别是在发展中国家，也对加拿大温暖而潮湿的夏天提出了很大的需求。电子设备中的冷却为新技术提供了进入市场的机会，因为功率密度和性能受到组件过热的限制。我们将对Marangoni对流对无柄液滴蒸发率的影响产生理解和量化，这对于广泛的应用将很有价值。这项研究将产生高素质的人员，这些人员精通热管理和能源领域，这对于许多不断扩大的加拿大行业来说都是重要的。