Investigation of temperature fluctuations caused by evaporating meniscus instabilities in two-phase heat transfer devices

在多孔结构中形成的液体薄膜的蒸发及其稳定性是由复杂的机制相互作用决定的，也是最具挑战性的研究问题之一。我们的主要目标是改善这一领域目前的基础知识，从而开发解决涉及薄膜蒸发的工业问题所需的工具。更好地了解这些现象的潜在物理机制对于进一步改进各种应用至关重要，包括电子、燃料电池和化学加工工业。*应用的重要领域之一是发电设备的热控制。随着新的电子设备产生更多的功率，也变得越来越小，使用传统的冷却技术来消除多余的热量变得更加困难。过高的工作温度会缩短电子设备的使用寿命，导致性能异常和设备故障。因此，需要更高效的热冷却技术。目前可用的最有效的热控制设备，如热管、回路热管和蒸汽室，都依赖于液体薄膜的蒸发。这些装置被用来转移产生热量的部件，如计算机的微处理器或航天器中的仪器，同时将温度保持在指定的范围内。与其他冷却技术相比，这些设备的优势包括不需要移动部件、坚固耐用以及能够传递大量热量。*然而，这些设备的一些操作方面仍然没有被很好地理解。与这些设备相关的主要问题之一是不受欢迎的温度波动。由于这些装置中发生的复杂现象，大多数人对这些波动的原因提出了定性的解释。温度波动是非常不受欢迎的，因为它们可能会阻碍散热能力或导致代价高昂的故障。*对薄膜稳定性的更好了解将使我们能够调查波动的原因并提出设计解决方案，以确保这些设备的稳定运行。我们以前的研究也表明，尽管界面不稳定性是最不受欢迎的，但利用界面不稳定性开发新的强化换热技术是可行的。这是一个非常有前景的研究领域，值得进一步深入研究。*这项研究将通过实验和数值调查进行，涉及两名博士和两名MASC学生的培训。重要的应用领域包括电子冷却，紧急情况下核反应堆的被动冷却，以及敏感空间有效载荷的热控制。

The evaporation of a liquid thin film formed in a porous structure and its stability are governed by a complex interaction of mechanisms and among the most challenging problems to study. Our primary goal is to improve the current fundamental knowledge in this field, and thus, to develop the required tools for solving industrial problems involving thin-film evaporation. A better understanding of the underlying physical mechanisms of these phenomena is critical to further improvements in a wide variety of applications, including electronics, fuel-cell, and chemical processing industries.***One of the important areas of application is the thermal control of power generating equipment. As new electronic devices are producing more power and also getting smaller, it is becoming more difficult to remove excess heat by using conventional cooling techniques. High operational temperatures can reduce the life time of electronics, cause performance anomalies and device failures. Therefore, there is a need for more efficient thermal cooling technologies. The most efficient thermal control devices currently available, such as heat pipes, loop heat pipes, and vapor chambers, rely on the evaporation of a liquid thin film. These devices have been used to transfer excess heat from a heat-producing component such as a microprocessor in a computer or an instrument in a spacecraft, while maintaining the temperature within a specified range. The advantages of these devices over other cooling techniques include lack of moving parts, robustness, and the ability to transfer large amounts of heat. ***However, some operational aspects of these devices are still not well understood. One of the major problems associated with these devices is the undesirable temperature fluctuations. Because of the complex phenomena taking place in these devices, mostly qualitative explanations have been proposed for origin of these fluctuations. The temperature fluctuations are highly undesirable as they may hinder the heat removal capacity or cause costly failures.***An improved understanding of the thin-film stability will allow us to investigate the origin of the fluctuations and propose design solutions to ensure a stable operation of these devices. Our previous research has also shown that although the interface instabilities are mostly undesirable, it is feasible to develop new heat transfer enhancement techniques by taking advantage of the instabilities. This is a highly promising area of research and deserves to be further investigated in more detail.***The research will be carried out through both experimental and numerical investigation and involve training of two PhD and two MASc students. The important application areas include electronics cooling, passive cooling of nuclear reactors after an emergency, and thermal control of sensitive space payloads.