EAGER: Experimental Methods and Measurements of Anomalous Properties of Supercritical Fluids and their Mixtures

在超临界条件下，不同的液相和气相不再存在，流体是增强热传递和有效热控制和管理的良好候选者。超临界热交换器在太阳能直接转换、发电、空间系统热管理等方面都是很有前途的解决方案。然而，由于缺乏对超临界传热异常行为的理解，超临界传热的研究受到限制，这些异常行为的特征是在临界点附近的一个区域内热物理性质的巨大变化，以及相关的热振荡和波动。这个EAGER项目将发展测量异常区域超临界特性的实验能力，以提高对超临界流体及其传热应用性能的基本理解。这个EAGER项目旨在探索：(i)利用异常行为来实现增强的传热，（ii）利用超临界压力的微小变化进行热管理和控制，以及（iii）改变超临界流体混合物的临界温度来调节热量消散的温度。项目任务是获取CO2与Ar和R134a混合的临界性质实验数据，并进行自然对流实验，论证异常区温度和压力的影响。如果成功，这个EAGER项目将为在极端温度下使用超临界流体混合物散热奠定基础，并使其应用于太阳能热电和发电系统。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Fluids under supercritical conditions, where distinct liquid and gas phases no longer exist, are good candidates for enhanced thermal transport and effective thermal control and management. Supercritical heat exchangers are promising solutions for direct solar energy conversion, power generation, thermal management of space systems, to name a few. However, research on supercritical heat transfer has been limited because of the lack of understanding of anomalous behaviors, characterized by large variations in thermophysical properties in a region around the critical point, and the associated thermal oscillations and fluctuations. This EAGER project will develop experimental capabilities to measure supercritical properties in the anomalous region to improve the fundamental understanding of supercritical fluids and their performance in heat transfer applications.This EAGER project seeks to explore: (i) the use of anomalous behavior to achieve enhanced heat transfer, (ii) thermal management and control using a small variation in supercritical pressure, and (iii) change in critical temperature of supercritical fluid mixture to tune the temperature at which the heat dissipates. The project tasks are to obtain experimental data on critical properties for mixtures of CO2 with Ar and R134a and conduct natural convection experiments to demonstrate the effect of temperature and pressure in the anomalous region. If successful, this EAGER project could build the foundation of using supercritical fluid mixtures for heat dissipation at extreme temperatures and enable applications in solar thermal and power generation systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.