HEAT TRANSFER IN FLUIDS AT NEAR-CRITICAL PRESSURES: EXPERIMENTS AND MATHEMATICAL MODELING

摘要：美国国家科学基金项目编号cst -0553571首席研究员沃里尔，加州大学洛杉矶分校，项目标题：近临界压力下流体的传热：实验和数学模型高压流体作为传热介质越来越多地应用于许多热化学过程，如低温冷却系统、热虹吸和大型超临界水冷堆（SCWR）。然而，在接近临界点时，由于流体性质的快速变化，实验结果既有强化传热，也有恶化传热。这些相互矛盾的结果的结果还不清楚。在这项基础研究中，将研究近临界压力下微尺度加热元件自然对流和沸腾过程中的传热机制。纹影摄影和粒子图像测速都将被采用。将根据实验数据开发适合设计目的的模型/相关性。除了实验外，还将使用直接数值模拟（DNS）进行数值模拟。在实验中获得的温度和速度数据将用于验证数值模拟。智力优势：提出的研究将极大地促进对临界压力附近流体传热的基本理解。所获得的知识将使学术界和工业界的研究人员更好地了解这一过程。这些知识的潜在创新应用包括微型热虹吸管和热管、低温冷却系统，以及更广泛意义上的SCWR在关闭模式和反应堆瞬态期间的热工水力系统。更广泛的影响：该项目将支持至少两名来自代表性不足群体的本科生在每年夏天来实验室工作。这将使学生有机会获得宝贵的实践经验，并激发他们对热科学与工程领域的兴趣。作为该项目的一部分，还将支持两名博士生。所完成的研究将在会议上提出，并在档案期刊上发表，供技术界普遍传播。

ABSTRACTNational Science FoundationProposal Number CTS-0553571Principal Investigator Warrier, GopinathAffiliation University of California-Los AngelesProposal Title Heat Transfer in Fluids at Near Critical Pressures: Experiments and Mathematical ModelingHigh pressure fluids are increasingly being promoted as heat transfer media in a number of thermal and chemical processes such as cryogenic cooling systems, thermosyphons, and large Supercritical Water-Cooled Reactors (SCWR). However, due to the rapid change in fluid properties close to the critical point, the experimental results have yielded both heat transfer enhancement and deterioration. The results for these contradictory results are not clearly understood. In this fundamental study, the heat transfer mechanisms involved during natural convection and boiling from microscale heater elements at near-critical pressures will be investigated. Both Schlieren photography and Particle Image Velocimetry will be employed. Models/correlations suitable for design purposes will be developed based on the experimental data. In addition to the experiments, numerical simulations using Direct Numerical Simulation (DNS) will also be performed. The temperature and velocity data obtained in the experiments will be used to validate the numerical simulations. Intellectual Merit: The proposed study will greatly advance the basic understanding of heat transfer in fluids at pressures near the critical pressure. The knowledge gained will provide researchers, in academia and industry, with a better understanding of the process. Potential innovative applications of this knowledge include miniature thermosyphons and heat pipes, cryogenic cooling systems, and in a broader sense SCWR thermal-hydraulics during shut down modes and reactor transients.Broader Impact: The project will support at least two undergraduate students from underrepresented groups to come and work in the laboratory during each summer. This will give the students a chance to gain valuable hands on experience and stimulate their interest in the field of thermal science and engineering. Two Ph.D. students will also be supported as part of this project. The research accomplished will be presented at conferences and published in archival journals for general dissemination by the technical community.