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

当一个下降的液膜从一个水平管流到另一个水平管时，它的模式（液滴、射流或薄片）对流体力学和传热有重大影响。没有完整的模型或经验基础来预测降膜模式，它的转变，或影响。所提出的研究旨在了解控制模态及其转变的物理参数，量化模态与传热之间的耦合，并为预测模态行为提供完整的基础。在这个实验程序中，在一个热控制的环境中，液体膜落在两个加热或冷却的试样管之间。对膜的位置、厚度和速度的测量，以及对周围蒸汽温度、压力、速度和传热的测量，表征了膜的下落及其影响。实验采用不同的工质、管径和间距、静态和强制流动、不同的热通量、液体质量流量和热力学条件进行。考察了候选参数对跃迁和迟滞的影响。研究了模态与传热之间的耦合关系，为评价模态及其效应提供了依据。

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.