Research Initiation Award: The Intertube Falling-Film Mode,Its Transition, Hysteresis, and Effect on Heat Transfer

当下降的液膜从一条水平管流到下面的另一条管子时，其模式(液滴、射流或薄片)对流体力学和换热有重要影响。没有完整的模型或经验基础来预测降膜模式、其转变或影响。这项研究旨在了解哪些物理参数控制着模式及其转变，量化模式与热传递之间的耦合，并为预测模式行为提供完整的基础。在这个实验程序中，液膜落在两个加热或冷却的试管之间，在一个热控制的环境中。对降膜位置、厚度和速度的测量，以及对周围蒸汽温度、压力、速度和热传递的测量，表征了降膜及其影响。实验在不同的工质、管径和间距下进行，在静止和强迫流动中进行，在不同的热通量、液体质量流量和热力学条件下进行。考察了候选参数对相变和磁滞的影响。研究了该模式与换热的耦合关系，为该模式及其效果的评价提供了依据。

When a falling liquid film flows from one horizontal tube to another below it, its mode (droplets, jets, or a sheet) has a significant impact on the hydrodynamics and heat transfer. There is no complete model or empirical basis for predicting the falling-film mode, its transitions, or effects. The proposed research is directed at understanding which physical parameters govern the mode and its transitions, quantifying the coupling between mode and heat transfer, and providing a complete basis for predicting mode behavior. In this experimental program, a liquid film falls between two heated or cooled specimen tubes in a thermally controlled environment. Measurements of film location, thickness, and velocity, along with measurements of the surrounding vapor temperature, pressure, velocity, and heat transfer, characterize the falling film and its influence. Experiments are conducted with different working media, tube diameters and spacings, and in quiescent and forced flows, with varying heat fluxes, liquid mass flow rates, and thermodynamic conditions. Candidate parameters are examined for their influence on transitions and hysteresis. Coupling between the mode and heat transfer are studied, to develop a basis for evaluating the mode and its effects.