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

在热交换器、核反应堆的部件和发生沸腾或冷凝的其他设备中，经常会遇到气体和液体的混合流动。这种流动非常复杂，但最近测量技术和计算方法的进步使人们能够深入研究它们的特征。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力学(CFD)方法来研究CANDU核电站所用的集箱-进料系统中的两相流动特性。主要的实验任务是：i)通过增加一个通用的联箱/进料器模型来修改现有的空气-水流动回路，其中可以选择不同的主动入口转塔和主动进料器的组合；ii)建立该模型进料管中气体和液体流量的测量数据库，同时记录转塔入口条件和联箱内的流动模式；以及iii)评估进料管内的流动障碍对气体和液体流量的影响。计算分析的主要任务是在与实验相同的进口流动条件和几何形状下对空气-水流动进行CFD模拟，并将模拟结果与测量结果进行比较，以验证CFD作为核安全分析感兴趣的条件和几何条件下的两相流模拟工具的适用性。拟议的实验和数字调查将使用最先进的工具进行，并将提高核反应堆设计者和安全分析员的技术能力。他们直接支持AECL的空气-水集头设施测试。它们还将协助加拿大核电业验证和改进现有的多阶段分析工具，并保持在世界经济这一领域的竞争地位。这笔赠款将使渥太华大学能够在核反应堆热工水力方面教育几名学生和其他人员，从而为核工业提供一批未来的高技能研究工程师，以取代目前即将退休的这类人员。

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.