Annular-Mist Flow Transport With Phase Change in Complex Fin-Matrix Passages

目前理解和预测复杂翅片基质通道中环状流两相输运的能力明显受限于目前缺乏关于这类流动中的脱落、夹带和沉积机制的信息。这些研究通过检查液体从翅片结构中排出的方式以及液体分解成液滴并分散到芯流中的方式来具体解决这一问题。正在开发微探针仪器，以获得关于翅片结构下游局部液滴密度和尺寸分布的定量信息，该仪器还将增强研究多相流传输的研究人员的一般能力。正在对翅片结构下游的夹带量和翅片与主要表面积之间的液体横向传输进行详细的定量测量，并对翅片基质通道中的汽化和冷凝流动进行现场测量。这些实验包括在很大的流动条件范围内同时测量纯冷却剂和二元混合物的对流汽化和冷凝的卷吸特性和整体换热。研究的最后阶段将使用实验中获得的数据来评估和改进现有的脱落、沉积和横向薄膜传输模型。这些改进的模型将被合并到用于预测整体传输的改进的计算方案中，以评估这些机制对基质中的热量和质量传输的影响。在拟议的研究中获得的有关液体传输机理的信息将有助于提高预测紧凑型蒸发器和冷凝器、冷却塔以及流动通道复杂和/或含有间断表面的其他设备中两相传输的能力。

The present capability to understand and predict two-phase transport for annular flow in complex fin-matrix passages is clearly limited by the current lack of information regarding the shedding, entrainment and deposition mechanisms in such flows. These studies address this problem specifically by examining the manner in which liquid is shed from fin structures and the way in which the liquid breaks-up into droplets and is dispersed into the core flow. Microprobe instrumentation is being developed to obtain quantitative information about local droplet density and size distribution downstream of fin structures, and this instrumentation will also augment the general capabilities of researchers working on multiphase flow transport. Detailed quantitative measurements of the entrainment downstream of fin-type structures and lateral transport of liquid between fins and prime surface areas, as well as in situ measurements in vaporizing and condensing flows in fin matrix passages are being made. These experiments include simultaneous measurement of entrainment characteristics and overall heat transfer for convective vaporization and condensation of pure coolants and binary mixtures over wide ranges of flow conditions. The final stage of the study will use data obtained in the experiments to assess and improve existing models of shedding, deposition and lateral film transport. These improved models will be incorporated into improved computational schemes for predicting the overall transport to evaluate the impact of these mechanisms on heat and mass transfer in the matrix. The information regarding liquid transport mechanisms obtained in the proposed research will serve to enhance the capabilities for predicting two-phase transport in compact evaporators and condensers, cooling towers, and other equipment in which the flow passages are complex and/or contain interrupted surfaces.