Experimental and computational studies of two-phase flows in nuclear reactor systems

气体和液体流的混合物通常在热交换器、核反应堆的部件以及其中发生沸腾或冷凝的其他设备中遇到。这种流动是非常复杂的，但最近在测量技术和计算方法的进步，允许深入研究其特性。本项目的目标是应用并进一步发展现有的实验和计算流体动力学（CFD）方法，以研究CANDU核电厂中使用的集管-给料系统中的两相流特性。 主要的实验任务是：i）通过增加一个通用的集管/进料器模型来修改现有的空气-水流动回路，在该模型中可以选择不同的主动入口塔和主动进料器的组合; ii）组装该模型的进料管中的气体和液体流速的测量数据库，同时还记录塔入口条件和集管内的流动模式;以及iii）评估进料管内的流动障碍物对气体和液体流速的影响。 计算分析的主要任务是在与实验相同的入口流动条件和相同的几何形状下对空气-水流进行CFD模拟，并将模拟结果与测量结果进行比较，以验证CFD作为两相流模拟工具在核安全分析所关注的条件和几何形状下的适用性。拟议的实验和数值研究将使用最先进的工具进行，并将提高核反应堆设计师和安全分析师的技术能力。它们直接支持AECL空气-水集管设施测试。它们还将协助加拿大核电工业验证和改进现有的多阶段分析工具，并在世界经济的这一领域保持竞争地位。这笔赠款将使uOttawa能够在核反应堆热工水力学方面教育几名学生和其他人员，从而为核工业提供一批高技能的研究工程师，以取代目前退休的这一代人员。

Mixtures of gas and liquid flows are commonly encountered in heat exchangers, in components of nuclear reactors and other equipment in which boiling or condensation occurs. Such flows are very complex, but recent advances in measurement techniques and computational methods have permitted an in-depth examination of their characteristics. The objective of this project is to apply, and further develop, available experimental and computational fluid dynamics (CFD) methods to the study of two-phase flow characteristics in header-feeder systems of the type used in CANDU nuclear power plants. The main experimental tasks are: i) to modify an existing air-water flow loop by the addition of a versatile header/feeder model, in which different combinations of active inlet turrets and active feeders can be selected; ii) to assemble a database of measurements of gas and liquid flow rates in the feeder tubes of this model, while also documenting the turret inlet conditions and the flow patterns inside the header; and iii) to assess the effect of flow obstructions inside feeder tubes on the gas and liquid flow rates. The main task of the computational analysis is to perform CFD simulations of air-water flows at the same inlet flow conditions and in the same geometries as those of the experiments and to compare the simulation results to the measurements to verify the applicability of CFD as a tool for two-phase flow simulation at conditions and geometries of interest to nuclear safety analysis. The proposed experimental and numerical investigations will be conducted using state-of-the-art tools and will advance the technical capabilities of nuclear reactor designers and safety analysts. They are in direct support of the AECL air-water header facility tests. They will also assist the Canadian nuclear power industry in validating and improving existing multi-phase analytical tools and in maintaining a competitive position in this field of the world economy. This grant will enable uOttawa to educate several students and other personnel in nuclear reactor thermalhydraulics, thus providing the nuclear industry with a pool of prospective highly skilled research engineers to replace the currently retiring generation of such personnel.