被動式概念的應用幾乎是從1980年代初被美國能源部推動，於Sodium Advanced Fast Reactor (SAFR, Rockwell International)及Power Reactor Inherent Safety Module (PRISM, General Electric)兩種型態的快中子核子反應堆的設計開始。經由自然界重力場、材料特性、物化性的差等因素作為驅動力，加上幾何或某些人為的設計，造成溫度場、壓力場、濃度場等的分布，在盡可能不需要外加動力驅動的原則下達成應用上或安全上的目的。
报告二：Numerical study of a novel fin configuration of a high temperature ceramic plate fin heat exchanger
报告人：Prof.Yitung Chen, Department of Mechanical Engineering, University of Nevada Las Vegas
High temperature heat exchanger (HTHE) is one of the most important components to transfer energy from one loop to the other loop in many highly efficient power and propulsion systems, such as the very high temperature gas-cooled reactor, the hydrogen production system with thermo-chemical cycle and the externally fired combined cycle. In the very high temperature gas-cooled reactor (VHTR) systems, it is an intermediate heat exchanger (IHX) that transfers the reactor core heat to the electricity generation system or hydrogen production system. In the hydrogen production system with thermochemical cycle, it is an integrated multi-step reactor that combines the functions of preheating, concentrating and decomposing of the sulfuric acid. In the externally fired gas turbine (EFGT) cycle and externally fired combined cycle (EFCC), it is a recuperator that preheats the clean compressed air for gas turbine by utilizing the energy of exhausted fuel gas. Many different concepts of HTHEs have been proposed and investigated by researchers, such as shell-and-tube heat exchanger, shell-and-plate microHTHE, printed circuit heat exchangers (PCHEs), ‘‘Offset-strip-fin’’ plate-fin heat exchangers and bayonet tube heat exchangers. Although the HTHEs in these systems have to comply with specific requirements, they are developing towards the direction of higher operating temperature. The flowing fluid is helium with operating pressure of being 7 MPa. As the fluid is heated from 850 K to 1250 K, the local velocity is increased by nearly 50% while the local Reynolds number is reduced by nearly 25% due to the variation of gas physical properties. It is different from the traditional low temperature heat exchanger because the heat transfer and fluid flow become periodical after a few entrance length. A set of different fin configurations applied on high temperature ceramic plate fin heat exchanger have been numerically studied and investigated to obtain the design information on heat transfer performance, pressure drop, and structural reliability. Results and discussions will be presented in the graduate seminar.
Prof. Yitung Chen简历：
Dr. Yitung Chen is Professor of Department of Mechanical Engineering at University of Nevada Las Vegas (UNLV) and an ASME Fellow. He received his Ph.D. degree from the Department of Mechanical Engineering at University of Utah in 1991. He has received more than $12.8M research funding from the U.S. DOE, NSF, DOD, EPA, NASA, NOAA, and private sectors. He has published two books, 6 book chapters, and more than 80 journal articles and 200 peer-review professional conference proceedings related to thermal-fluid, nuclear, solar and wind energy, and corrosion modeling areas. He has received many outstanding teaching and research awards and the best scholar award during his tenure at UNLV. He is also Co-Director of Center for Energy Research at UNLV.