圆管内油-气-水三相弹状流液弹区流动特性的研究

利用液弹内气体平衡关系，建立油－气－水三相流液弹平均含气率的物理模型。同时利用光导纤维探针法，详细测定各种工况下稳态弹状流液弹的含气率局部分布规律；并通过变换探针的径向位置，研究液弹含气率沿液弹长度的空间变化规律，从细观上揭示油、气、水三相弹状流流弹区流动特性。     

微通道内单相流流动特性的实验研究进展

基于微小/微通道内的流动特性,概述了目前国内外关于微小/微换热器中采用不同管道截面类型(圆形,矩形,梯形等)时的单相流流动特性的实验研究进展,总结了微小/微通道内的流体流动规律,指出影响其流动特性的主要因素是粗糙度,层流向湍流的转折提前以及实验数据处理方式,并给出了下一步的工作建议.     

矩形微通道内气液两相流压力降特性

以氮气为气相介质,以不同表面张力的液体(纯水、0.01%SDS溶液、乙醇)为液相介质,对3种矩形微通道(200μm×200μm,400μm×400μm和800μm×800μm)内两相流压力降进行可视化试验,同时对微通道内两相流压力降梯度进行了测量,并将测量值与均相流模型、分相流模型和以流型为基础模型的预测值进行了对比.结果表明:两相流压力降受表面张力、通道尺寸和两相流速度影响;以流型为基础模型的理论预测方法预测效果最好.     

水平管内油气水三相泡状流-弹状流转换的研究

结合压差波动法识别流型，对水平管内油-气-水三相泡状流-弹状流转换特性进行了理论和实验研究，建立了泡状流向弹状流转变的界线方程，结果表明，泡状流向弹状流转变的主要因素不仅包括气相折算速度和液相折算速度，而且含油率与管径也起重要作用，计算结果与实验结果基本相吻合。     

多孔微通道流动沸腾换热特性的实验研究

本文通过实验的方法对烧结的多孔微通道和铜基微通道的沸腾换热性能和流动不稳定进行研究.实验工质选用去离子水,采用的铜粉粒径分别为30μm、50μm、90 μm,烧结底厚为200 μm和400 μm.采取控制变量的方式,研究改变入口温度、铜粉粒径大小、入口流量对多孔微通道和铜基微通道换热性能的影响.研究表明:多孔微通道最优的厚度粒径比在2～5之间,在此区间的多孔微通道可以提高沸腾传热的性能.其中厚度粒径比为2和4的多孔微通道的最大换热系数是铜基微通道的换热系数的5倍.多孔微通道相对于铜基微通道有更好的换热能力,有着较低的壁面温度.     

微通道内流动沸腾特性研究

对国内外微通道流动和换热的研究实验作了总结,阐述了影响微通道换热系数的因素,如热流密度、过热度和干度等.对去离子水在内径为0.65 mm、长为102 mm的圆形管道内流动沸腾换热进行了实验研究,得到了局部换热系数随干度的变化关系,进而根据换热系数的变化趋势讨论了饱和流动沸腾区微通道内主导的换热机制.结果表明:从换热系数随干度的变化关系很难判定主导的换热机制;将实验数据与已发表的预测关联式进行了比较,发现大多关联式都失效,说明基于常规理论的模型不再适用于微通道.     

微尺度通道内流动沸腾研究综述

阐述了微尺度通道内传热问题出现的工程背景——高密度微电子器件的冷却。对当前国内外微尺度通道内流动沸腾换热特性的研究现状进行了归纳。突出分析了工质种类、微尺度通道的几何参数和工质的工况参数等对微尺度通道内流动沸腾换热特性的影响。同时分析了微尺度通道内流动沸腾换热的强化机理、流动阻力特性、压降关联式和沸腾换热关联式的理论和实验研究。最后根据分析对今后的工作提出了一些建议。     

微通道和小通道内流动沸腾换热的研究

介绍了小通道、微通道内流动沸腾换热机理的最新进展，其中包括国内外学者对各种形状的单通道小通道内流动沸腾现象的解释及其对换热系数影响的各种不同看法，以及微通道内流动沸腾换热现象研究的概况；还介绍了小通道和微通道内流型转变的研究现状，指出了各研究者研究结果的差异，并提出要进一步探索小通道微通道内流动沸腾换热现象，必须借助更先进的观测手段等。     

Experimental study for the stratified to slug flow regime transition mechanism of gas-oil two-phase flow in horizontal pipe

Theoretical relations that predict the transition from a stratified pattern to a slug pattern, including a onedimensional wave model that contains less empiricism than the commonly used Taitel-Dukler model, and the ideal model for stratified flow for the gas-liquid flow in horizontal pipes are presented. Superficial velocities of each phase, as the onset of slugging occurs, were predicted, and theoretical analysis was conducted on the stratified to slug flow regime transition. The friction, existing between the fluid and pipe wall, and on the interface of two phases, was especially taken into account. A theoretical model was applied to an experiment about air-oil two-phase flow in a 50 mm horizontal pipe. The effect of pipe diameter on the transition was also studied. The results show that this approach gives a reasonable prediction over the whole range of flow rates, and better agreement has been achieved between predicted and measured critical parameters. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(10): 1782–1785, 1789 [译自: 上海交通大学学报]     

Continuity wave in the elongated bubble region of horizontal slug flow

Visualized observation on the wave feature in a horizontal slug flow was made with a high‐speed digital camera. It was found that the liquid film flow in the elongated bubble region of slug flow behaves as a continuity wave. Theoretical analysis was carried out and it reveals that the liquid film flow is a continuity wave with celerity the same as the translational velocity of the elongated bubble. The control equation for the liquid film height in the elongated bubble region was derived. The results predicted by the equation fit well with the observed data. A new conclusion was obtained that slug flow has continuity wave in it, explaining the stable slug flow wave characterization. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(8): 547–554, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20092     

Delaying modified QUICK scheme and its application in slug flow

IntroductionGas-liquid flow in pipes may aPPear in variousconfigUrations detennined by the spatial distribution ofthe twO Phase in the pipes. These coal~ons aretermed as flow patterns. Slug flow eaistS over a broadrange of gas and liquid flow rates and is encountered in awide vallely of industrial aPPlications.lh venical slug flow, most of thp gas is located inlarge bullet{shaped bubbles, the so called Taylor bubbles,Which occupy most of the pipe cross section. The liquidconfined betWeen …     

跨努森数区域的微通道内流动计算模拟研究

采用一阶和修正二阶的滑移连续介质模型,对跨努森数区域的低速微通道流进行二维和三维数值模拟。用实验结果和DSMC方法验证滑移连续介质模型在跨努森数区域中的适用性,并详细讨论了微通道流的可压缩效应、稀薄效应、低雷诺数效应和三维特性。研究表明,努森数是表征稀薄效应和模型适用性的特征参数,滑移连续介质模型适用于努森数小于0.150的氮气流动;马赫数不再是微通道流可压缩效应的唯一标识参数;雷诺数是表征低雷诺数效应和三维特性的关键参数,高宽比大于20的微通道流具备良好的二维特性。     

Structure and void fraction in a liquid slug for gas–liquid two‐phase slug flow

The distribution of gas and liquid in a gas–liquid two‐phase slug flow was measured using semi‐supermultiple point‐electrode probes. Based on the measurements, the wake zone behind a gas slug and the low void‐fraction zone in a liquid slug were defined, and the void fractions of the two zones were determined. The data revealed that the void fraction of the wake zone increased with superficial gas velocity, yet was virtually independent of superficial liquid velocity. Nondimensional head was proposed as an informative characteristic of this system, accounting for the momentum change of the liquid in the wake zone. It was clarified that the nondimensional head was closely related to the void fraction of the wake zone. A good practical relationship was found between the nondimensional head and the lengths of a swelling liquid‐front zone and the wake zone. Furthermore, empirical correlations were proposed for the void fraction in the wake zone, the mean void fraction in the liquid slug, and the lengths of the swelling liquid‐front zone and the wake zone. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 257–271, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10029     

Internal flow structure description of slug flow-pattern in a horizontal pipe

Utility of the hot-film anemometry technique in describing the internal flow structure of a horizontal slug flow-pattern is discussed within the scope of intermittent nature of slug flow. It is shown that a single probe can be used for identifying the gas and liquid phases and for differentiating the large elongated bubble group from the small bubbles present in the liquid slug. Analyzing the nature of voltage signals, a signal processing scheme is developed for measurements of time-averaged void fractions of small and large bubbles as well as for the measurements of local mean axial velocity and turbulent intensity in the liquid phase. Some results of local measurements of time-averaged void fractions of small and large bubble groups, axial mean velocity and turbulent intensity are presented at relatively low and high gas and liquid flows for a horizontal slug flow-pattern in a 50.3 mm i.d. pipe.     

A study on un‐fully developed slug flow in a vertical tube

Gas‐liquid co‐current vertical slug flow was studied in a vertical Plexiglas tube. Taylor bubbles and liquid slug lengths and their rising velocities were measured by means of a pair of conductivity probes under un‐fully developed flow conditions. The influences of the superficial velocity of gas and liquid on slug flow parameters were examined. Using statistical analysis on the length of Taylor bubbles, the probability distribution of the length of the Taylor bubbles was obtained, which obeyed a normal distribution under a significance level of α = 0.05. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(4): 235–242, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20063     

多管程微通道冷凝器热力性能计算方法

多管程平行流微通道冷凝器的管程设计方案对换热器管内热力性能影响较大。但目前一直尚未有对其管内换热系数和压降进行理论预测的较为简单可行方法。本文针对各管程工质流量可变,平均干度可变的多管程平行流冷凝器管内热力参数提出一种分程计算方法：在假设管壁温度不变及同管程内流量均匀分配的前提下,采用了Koyama与Wang冷凝换热模型,以及Zhang和Koyama提出的摩擦压降模型,建立了壁温与热流量之间的关系式,通过迭代求得管内平均换热系数和压降的理论值。以一个商用R134a、流程分配为12-8-8-6微通道冷凝器作为示例,用理论和实验方法分别得到了其管内冷凝平均换热系数和压降。结果表明,二者的偏差均落在30%以内。其中Koyama和Zhang 提出的模型预测偏差较小,分别为-4.96%~11.31%,0.42%~25.14%。     

An inspection of viscosity model for homogeneous two-phase flow pressure drop prediction in a horizontal circular micro-channel

This study analyzes several well-known two-phase viscosity models in order to address the appropriate correlations among them for application to micro-channel. Pressure drop data is obtained from adiabatic two-phase air–water flow experiments. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The measured data is compared with the homogeneous flow predictions calculated using the existing viscosity models and detailed comparisons are discussed.     

Shape of isolated bubble in intermittent flows in a horizontal pipe

An experimental study on the shape of a single bubble similar to those observed in a horizontal plug/slug flow was performed using visual observation and conductance probes. The results indicated that the shapes of the bubble nose and the bubble body depend on the Froude number defined by gas/liquid mixture velocity, whereas the shape of the back region of the bubble depends on both the Froude number and bubble length. The photographic images showed that the structural feature of the bubble head is related to the motion characteristics of the bubble. The transition from plug flow to slug flow occurs when the tail of the bubble changes from a staircase to hydraulic jump pattern with the increasing of the Froude number and bubble length. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 276– 285, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20161