STTR Phase II: Condensation on Gradient Surfaces

这个小企业技术转移研究（STTR）第二阶段项目提出了创新的传热研究，涉及润湿性梯度上的滴状冷凝。 单独的滴状冷凝已经显示出比膜状冷凝增加一个数量级的冷凝传热系数的能力，典型的垂直热虹吸管。 在梯度表面上冷凝的液滴经历不同的接触角，导致液滴在增加的润湿性的方向上加速到高速度。 冷凝液滴的相对侧上的接触角的差异是由于冷凝表面的局部变化的性质，其由具有低表面能的分子的变化的表面浓度控制。 在梯度表面上冷凝所引起的较高的液滴速度进一步增加了典型滴状冷凝的传热系数。 此外，梯度表面不需要重力来从冷凝表面去除液体，从而能够在水平表面上和微重力应用中实现逐滴冷凝热传递。 在本提案中，第一阶段中展示的技术将被集成到适用于电子冷却的蒸汽室传热设备中。该项目的更广泛影响/商业潜力将在热管理行业中感受到。 具体而言，结合这一创新将能够显着提高蒸汽室的热性能，从而节省成本，并提高许多行业的性能。 在计算行业，笔记本电脑和服务器的解决方案越来越受到热问题的限制。 在微重力环境中，这些新的梯度表面将取代或增强目前用于通信卫星应用的热管装置，如轴向槽热管和回路热管中的毛细力。 在核工业中，更有效的冷凝直接提高了电力转换效率。 已经存在对更高容量热解决方案的需求，并且随着商业实体和政府机构扩展其能力并要求更大的散热，这种需求只会增加。 这项开发工作还将增强对由于表面梯度和类似的马兰戈尼流动引起的液体运动的基本理解，这将对各个领域产生影响，包括与微流体应用中的流体泵送相关的研究。

This Small Business Technology Transfer Research (STTR) Phase II project proposes innovative heat transfer research involving dropwise condensation on a wettability gradient. Dropwise condensation alone has shown the ability to increase condensation heat transfer coefficients by an order of magnitude over film condensation, typical of vertical thermosyphons. Droplets condensing on a gradient surface experience different contact angles, causing the droplets to accelerate to high velocities in the direction of increased wettability. The difference in contact angle on opposite sides of the condensing droplets is due to locally varying properties of the condensing surface, controlled by varying surface concentrations of molecules with low surface energy. The higher droplet velocities caused by condensing on the gradient surface further increases the heat transfer coefficient over typical dropwise condensation. Furthermore, the gradient surface does not require gravity to remove liquid from the condensing surface, enabling dropwise condensation heat transfer on horizontal surfaces and in microgravity applications. In this proposal, the technology demonstrated in Phase I will be integrated into a vapor chamber heat transfer device suitable for electronics cooling.The broader impact/commercial potential of this project will be felt in the thermal management industry. Specifically, incorporating this innovation will enable significantly improved thermal performance in vapor chambers, leading to cost savings and allowing improved performance in a number of industries. In the computing industry, solutions for notebook computers and servers are becoming increasingly limited by thermal issues. In micro-gravity environments, these new gradient surfaces will replace or enhance the capillary forces currently used in heat pipe devices, such as axially grooved heat pipes and loop heat pipes, for communication satellite applications. In the nuclear industry, more efficient condensation directly increases electrical conversion efficiency. There is already a demand for higher capacity thermal solutions, and this demand will only increase as commercial entities and government agencies expand their capabilities and demand greater thermal dissipation. This development effort will also enhance the fundamental understanding of liquid movements due to surface gradients and similar Marangoni flows, which will have an impact in various fields, including research related to fluid pumping in micro-fluidic applications.