HEAT AND MASS TRANSFER IN TRANSITIONAL TWO PHASE FLOWS

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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.