Condensation Heat Transfer from Humid Air to a Horizontal tube

从潮湿空气到水平管的冷凝传热

• 批准号: 60550158
• 负责人: NAGATA Takashi
• 金额: $ 0.96万
• 依托单位: University of the Ryukyus
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550158/
• 关键词: Humid Air; Condensation Heat Transfer; A Horizontal Tube; Laminar Film Condensation; Numerical Analysis; Similarity Solution; Samll Temperature Difference Type Heat Exchanger

The present project deals with both the experimental study of heat and mass transfer from humid air to a horizontal tube and numerical analysis of laminar film condensation of water vapor in humid air flowing on a flat plate. The study aims at the establishment of the design method of a small temperature difference type heat exchanger in which humid air is cooled and dehumidified. Main results obtained in experiments and numerical analysis are summerized as follows:(1) Condensation pattern such as film, drop and mixed wise in the cooling test much depends on surface condition of test tube, however, little effect on heat transfer due to small amount of vapor content.(2) Sherwood number for mass transfer and Nusselt number for convective heat transfer are shown as function of Reynolds number in the figure.(3) From the analysis of temperature and mass concentration distributions in the boundary layer of vapor -air mixtures, there exists thermodynamically a supper saturated state near the interface, but it actually will tend to a saturation state by formation of fog.(4) It became clear that temperature difference between the interface and the wall is so small and little ffect of condensation on convective heat trasfer is recognized.(5) Nondimentional correlations on heat and mass transfer are obtained from similarity solutions, then total heat transfer is to be estimated by combining them,

本文对湿空气在水平管内的传热传质过程进行了实验研究，并对水蒸气在湿空气平板上的层流膜状冷凝过程进行了数值分析。研究旨在建立一种用于湿空气冷却除湿的小温差式换热器的设计方法。实验和数值分析的主要结果如下：（1）在冷却试验中，冷凝形式主要取决于管壁表面状况，而由于管内水蒸气含量较少，对传热影响不大。(2)图中显示了用于传质的舍伍德数和用于对流传热的努塞尔数作为雷诺数的函数。(3)通过对水汽-空气混合物边界层内温度和质量浓度分布的分析，发现在界面附近存在一个过饱和状态，但实际上由于雾的形成，它会趋于饱和状态。(4)结果表明，界面与壁面之间的温差很小，冷凝对对流换热的影响很小。(5)由相似解得到传热传质的无因次关联式，然后将它们结合起来估算总传热量，