HEAT AND MASS TRANSFER IN TRANSITIONAL TWO PHASE FLOWS

两相气液流在许多工程应用中很常见，例如发电厂、热交换器和许多化学工艺系统。 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的几何构造布置的突然的面积变化、弯曲和接头。由于相再分布、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可能是复杂的，这可能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是重要的，因为失效的关键区域经常发生在这些部件中。例如，需要了解蒸汽发生器中歧管和U形弯管中的两相传热，以避免干燥，而传质是流动加速腐蚀中管壁减薄的速率限制因素。因此，重要的是要了解在这种过渡的两相流的流动和热/质传递，以开发机械模型，并适当地设计这样的两相系统。本提案的总体目标是调查常见的两相系统中发现的这些组件中的流动和热/质传递。实验将在现有的1英寸和8英寸直径的空气-水流动回路中进行。8英寸直径的垂直空气-水回路是一个独特的测试设施，也是世界各地研究型大学中为数不多的此类设施之一，这将允许在更具有工业代表性的规模上进行研究。测量将包括相再分布和局部空隙和压力分布，壁面剪切应力和热/质传递。这些测量的基础设施和方法是多年来在内部开发的。将在这里进行的测量将是独特的，并提供了一个更好的理解的因果效应的两相流的热量和质量传递，这将允许更好的机制建模这种复杂的现象。

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.