HEAT AND MASS TRANSFER IN TRANSITIONAL TWO PHASE FLOWS

气液两相流动在许多工程应用中是常见的，例如在发电厂、热交换器和许多化工过程系统中。在这些和其他应用中，两相流可以发生在复杂的管道几何形状中，例如在一系列流动条件下以不同几何形状排列的弯头和连接点。由于气相的再分布、气相的可压缩性和二次流的产生，这种过渡管道部件中的两相流动可能是复杂的，这可能会显著影响传热和传质特性。这种过渡管道部件中的传热和传质非常重要，因为这些部件经常出现故障的关键区域。例如，为了避免干涸，需要了解蒸汽发生器歧管和U型弯管中的两相换热，而传质是流动加速腐蚀中管壁减薄的速度限制因素。因此，了解这类过渡两相流中的流动和传热传质过程，对于建立机理模型和合理设计这类两相系统具有重要意义。该方案的总体目标是研究常见两相系统中此类组分的流动和热/质传递。实验将在现有的1英寸和8英寸直径的空气-水流动环路中进行。直径8英寸的垂直空气-水循环是一种独特的测试设施，也是世界各地研究型大学为数不多的此类设施之一，它将允许在更具行业代表性的规模上进行研究。测量将包括相重分布和局部空隙和压力分布，壁面剪应力和热/质传递。多年来，这些测量的基础设施和方法都是内部开发的。这里进行的测量将是独一无二的，可以更好地了解两相流对热量和质量传递的因果影响，这将允许更好地对这一复杂现象进行机械建模。

Two phase gas-liquid flows are common in a number of engineering applications, such as in power generation plants, heat exchangers, and many chemical process systems. In these and other applications, the two phase flow can occur in complex piping geometries such as sudden area changes, bends and junctions arranged in different geometric configurations under a range of flow conditions. The two phase flow in such transitional piping components can be complex, due to phase re-distributions, compressibility of the gas phase and the generation of secondary flows, which can significantly affect the heat and mass transfer characteristics. The heat and mass transfer in such transitional piping components are important since the critical regions of failure often occur in these components. For example, the understanding of the two phase heat transfer in manifolds and U-bends in steam generators is required to avoid dryout, while the mass transfer is the rate limiting factor for pipe wall thinning in flow accelerated corrosion. Thus, it is important to understand the flow and heat/mass transfer in such transitional two phase flows to develop mechanistic models and properly design such two phase systems. The overall objective of this proposal is to investigate the flow and heat/mass transfer in such components found in common two phase systems. Experiments will be performed in existing 1- and 8- inch diameter air-water flow loops. The 8 inch diameter vertical air-water loop is a unique test facility, and one of few such facilities in research universities around the world, which will allow study at scales more representative of industry. The measurements will include phase re-distribution and local void and pressure distribution, wall shear stress and heat/mass transfer. The infrastructure and methodology for these measurements has been developed in-house over a number of years. The measurements that will be performed here will be unique and provide a better understanding of the causal effects of the two phase flow on the heat and mass transfer, which will allow better mechanistic modeling of this complex phenomena.