ISS: Constrained Vapor Bubbles of Ideal Mixtures

Plawsky, Joel l .热管是一种传热装置，经常用于冷却各种电子设备，包括笔记本电脑。热管是用流体来传递热量的，但这种装置的一个基本特征是流体在液体和蒸汽之间发生相变。液体和蒸汽的详细运动，以及两相之间界面的运动和动力学，可以强烈地影响热管和类似系统的性能。最近的研究结果表明，使用流体混合物，而不是纯流体，可以帮助克服多相传热系统的性能限制和意外故障。该项目将使用国际空间站（ISS）上的约束蒸汽泡系统来检查有机流体混合物的各种界面现象。在地球上进行的平行实验将有助于揭示重力对界面动力学和传热性能特征的影响。该项目的结果将为从业者提供可用于改进相变传热和传质操作的信息，相变传热和传质操作在能量转换、蒸馏、微电子冷却、涂层工艺和空间探索等领域变得越来越重要。该项目还将为学生提供机会，通过伦斯勒大学的本科生研究计划参与研究。本项目将研究无套管热管中戊烷/异己烷流体混合物的界面现象和热流体性能。在地球和国际空间站上进行的平行实验将解决一些基本问题，包括马兰戈尼力对流体运动和设备性能的影响。凝结和莱顿弗罗斯特液滴的存在在设备的热端是特别感兴趣的。该项目将检查接近50:50成分的混合物，地面实验表明这种混合物的行为与理想混合物的行为有偏差。这些偏差将在微重力下被放大，并将改变无芯热管的界面特性和传热性能。实验将使用多波长干涉测量法绘制汽液界面图。该技术可以隔离驱动流体流动的曲率梯度，并可以确定在整个装置中存在的液体半月板内是否发生局部相变。将特别关注装置加热端附近的区域，在那里，马兰戈尼力和毛细力之间的竞争可能导致性能的新限制，并且在那里，分离压力/分子间力效应似乎会促进意外的冷凝。界面映射将与温度分布测量相结合，以了解并最终预测这些器件的热性能。利用静止运动和视频应用的干涉测量技术，液体半月板的稳定性和稳定性如何依赖于热输入和液体成分将被探索。将开发热流体模型，以帮助解释半月板和设备水平的观测结果。该项目的结果将导致设计更好的热管理设备，依赖于相变传热，将有助于概述蒸发和冷凝过程的限制，液体半月板的稳定性，以及理想流体混合物近似的适用性，相平衡热力学的基石之一。

CBET - 1637816PI: Plawsky, Joel L.Heat pipes are heat transfer devices that are used regularly for cooling a variety of electronic equipment, including laptop computers. Heat pipes use a fluid to transfer heat, but an essential feature of the device is that the fluid undergoes change of phase between liquid and vapor. The detailed motion of the liquid and vapor, and the motion and dynamics of the interface between the two phases, can strongly affect the performance of heat pipes and similar systems. Recent results suggest that the use of a fluid mixture, instead of a pure fluid, can help overcome limitations on performance and unanticipated failures of multiphase heat transfer systems. This project will use the constrained vapor bubble system on board the International Space Station (ISS) to examine various interfacial phenomena for mixtures of organic fluids. Parallel experiments conducted on Earth will help reveal the influence of gravity on interfacial dynamics and heat transfer performance characteristics. Results from the project will provide information that practitioners can use to improve phase-change heat and mass transfer operations, which are becoming increasingly important in fields such as energy conversion, distillation, microelectronics cooling, coating processes, and space exploration. The project will also provide opportunities for students to participate in research through Rensselaer's Undergraduate Research Program. This project will investigate interfacial phenomena and thermal-fluid performance for pentane/isohexane fluid mixtures in a wickless heat pipe. Parallel experiments on Earth and on the ISS will address fundamental issues, including the effects of Marangoni forces on fluid motion and device performance. Condensation and the presence of Leidenfrost droplets at the hot ends of the device are of particular interest. The project will examine mixtures near 50:50 composition for which ground-based experiments have shown deviations from ideal mixture behavior. These deviations will be magnified in microgravity and will alter interfacial characteristics and heat transfer performance of the wickless heat pipe. The experiments will map the vapor-liquid interface using multi-wavelength interferometry. This technique can isolate curvature gradients that drive fluid flow and can determine whether a phase change is occurring locally within the liquid menisci present throughout the device. Particular focus will be given to regions near the heated end of the device where the competition between Marangoni and capillary forces can lead to a new limitation on performance and where disjoining pressure/intermolecular force effects appear to promote unexpected condensation. The interface mapping will be combined with temperature profile measurements to understand, and ultimately predict, the thermal performance of these devices. Using stopped motion and video applications of the interferometry technique, the stability of the liquid menisci and how stability depends upon heat input and liquid composition will be explored. Thermal-fluid models will be developed to help explain the observations both at the meniscus and the device levels. Results of the project will lead to the design of better thermal management devices that rely on phase change heat transfer and will help outline the limits of evaporation and condensation processes, the stability of liquid menisci, and the applicability of the ideal fluid mixture approximation, one of the cornerstones of phase equilibrium thermodynamics.