倾斜下降管内油气水三相流流型转变的实验研究

对倾斜下降管倾角变化对油气水三相流流型转变的影响进行了研究 ,通过大量实验得到流型图 ,发现倾角对流型转变有重大影响 :倾角增大到 3 0°时 ,增大气流量 ,泡状流已不再转变为间歇流 ,而是分层流 ;倾角变化对环状流和间歇流之间的转变影响显著。得到的界限方程规律与实验现象及流型图符合良好     

Influence of tube inclination on the flow regime boundaries of condensing steam

Flow regime data of condensing steam inside an inclined 13.4 mm ID tube are presented. The effect of upward and downward inclinations within ± 10° on the different transition lines is discussed. In all test runs, complete condensation has been achieved inside the condenser, with or without full tube at exit depending on the total mass flow rate and inclination angle. It is shown that the zones occupied by the wavy and slug regimes experience significant shifts, whereas the effect on the annular flow boundary appears to be insignificant at the present small inclination angles. The present data sets are compared with adiabatic gas-liquid flow regime maps developed analytically and experimentally for horizontal and inclined tubes. Deviations due to the condensation process are observed; however, consistent trends are identified among the two types of flow.     

Experiments on the suspension of spheres in inclined tubes—II. Suspension by air

Data are presented on the suspension of single spheres by air, in inclined tubes ranging in diameter from 0·97 to 5·13 cm. The angle of inclination of the tubes to the horizontal axis varied from 0 to 90°. The data, which relate the pressure drop and suspending velocity to the geometric and physical parameters of the system, are compared with data generated previously using water as the suspending fluid. Dimensionless expressions are presented which correlate both sets of data for pressure drop and suspending velocity in terms of sphere/tube diameter ratio, tube diameter, density of solid and fluid and angle of inclination of the tube.     

Numerical Simulations of the Effect of Conical Dimension on the Hydrodynamic Behaviour in Spouted Beds

The flow behaviours of gas‐solids were predicted by means of a hydrodynamic model of dense gas‐solid flow in spouted beds. Constitutive equations describing the particulate solids pressure and viscosity were implemented into a hydrodynamic simulation computer program. The effect of operating conditions (inclined angle and gas spouting velocity) on particle velocity and concentration in the spout, annulus and fountain regions were numerical studied. Both vertical and horizontal particle velocities increased with increasing spouting gas velocity. The diameter of the spout increases with decreasing the inclination angle. As the inclination angle is set greater than 60°, the spout cross‐section starts becoming bottlenecked, limiting the upwards flow of solids.     

Effect of pipe orientation on dense-phase transport in inclined upward and downward flows

A physical model is presented to describe the flow characteristics of cocurrent two-layer upflow and downflow through inclined tubes. The influence of inclination angle on these two kinds of flow patterns has been investigated. For inclined upflow, the solids/gas velocity ratio is less than unity and decreases slightly with the increase of inclination angle, whereas for inclined downflow, this velocity ratio is, in general, greater than unity and increases with the inclination angle. The average voidage increases as the inclination angle decreases for inclined upflow while an opposite trend exists for inclined downflow. The pressure gradient is invariably negative for inclined upflow at various inclination angles and for inclined downflow of low inclination; however, the gradient becomes positive for inclined downflow at higher inclination angles. A flow regime map has also been presented. The present predictions agree well with the existing published experimental results.     

低温向上倾斜管内Taylor泡初始形成位置分布的实验研究

An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using the high speed digital camera. The tubes in the experiment are 0.018 m and 0.014 m in inner diameter and 1.0 m in length. The range of the inclination angles is 0-45° from the vertical. The statistical method is employed to analyze the experimental data. The experiment was focused on the effect of the inclination angle on the initial position distribution of Taylor bubbles. The formation criterion of Taylor bubbles was confirmed by analyzing the images of Taylor bubbles. The experimental results show that the initial position of Taylor bubble increased first, and then decreased with the increasing inclination angle, with the maximum at 30°. The standard deviation of the initial position of Taylor bubble in tubes was different with different inner diameters. The lognormal shape was fitted to the measured the initial position distributions of Taylor bubbles in the cryogenic tubes.     

加热面倾斜角对过冷沸腾中汽泡生长-冷凝行为的影响

采用高速摄影的方式,对矩形通道内过冷沸腾时的汽泡在倾斜状态下的行为进行了可视化研究,分析了加热面倾斜角度对汽泡生长-冷凝速率以及平均汽泡最大直径与对应生长时间的影响。结果表明:在同一入口工况参数下,汽泡的最大直径与寿期均随角度的增加而上升,且与倾斜角度近似呈正比;不同倾斜条件下的汽泡最大直径与对应生长时间基本满足0.5次幂的函数关系,其系数与倾斜角度呈正比;采用Zuber量纲1形式表示后,不同倾角时的平均汽泡生长-冷凝曲线在生长阶段随倾角增加而增加,而在冷凝阶段则与角度无明显关联。     

EFFECT OF PIPE ORIENTATION ON DENSE-PHASE TRANSPORT IN INCLINED UPWARD AND DOWNWARD FLOWS

A physical model is presented to describe the flow characteristics of cocurrent two-layer upflow and downflow through inclined tubes. The influence of inclination angle on these two kinds of flow patterns has been investigated. For inclined upflow, the solids/gas velocity ratio is less than unity and decreases slightly with the increase of inclination angle, whereas for inclined downflow, this velocity ratio is, in general, greater than unity and increases with the inclination angle. The average voidage increases as the inclination angle decreases for inclined upflow while an opposite trend exists for inclined downflow. The pressure gradient is invariably negative for inclined upflow at various inclination angles and for inclined downflow of low inclination; however, the gradient becomes positive for inclined downflow at higher inclination angles. A flow regime map has also been presented. The present predictions agree well with the existing published experimental results.     

Modeling of low viscosity oil-water annular flow in horizontal and slightly inclined pipes: Experiments and CFD simulations

To characterize the effect of pipe inclination, low viscosity, flow rate and inlet water cut on annular flow pattern, a low viscosity oil-water two-phase annular flow in horizontal and slightly inclined (+1°, +3° and +5°) pipes with diameter of 20 mm has been experimentally investigated. A modified VOF model based on the CFD software package FLUENT was used to predict the in-situ oil fraction and pressure drop. The experimental data indicate that annular flow appears at a medium-high water cut. The slip ratio increases with flow rate increase but decreases with increasing water cut. The changes are more significant as the degree of inclination increases. Pressure drop is strongly dependent on flow rate, as it increases rapidly as inlet flow rate increase. Good agreement between the experimental data and calculated results of slip ratio and pressure drop was obtained.     

A prediction model for the critical gas velocity and pressure gradient of continuous liquid-carrying in inclined pipes

A generic model for the prediction of critical gas velocity and pressure gradient in slightly inclined pipes (β ≤ 6°) is presented in this article. The gas–liquid configuration was determined based on the minimum energy principle and consideration of wettability and surface tension. A visualization experiment was conducted to obtain the critical gas velocity and the critical pressure gradient of a gas–liquid flow through the 40 and 60-mm pipe diameter. The theoretical study shows that the configuration is close to a convex interface shape at the critical conditions, which is in accord with the experimental phenomenon. Experimental study shows interfacial waves are the main cause of increased interfacial friction factor and a linear functional relationship between the inclination angle and the flow correction factor f(β). The results demonstrate that the new model is capable of providing satisfactory prediction results for the critical gas velocity, pressure drop, and liquid holdup.     

大流量下倾斜管气液两相流实验研究

在较高的气液范围内,以水和空气为实验介质,在多相流实验平台上进行了倾斜向上的高产量气液两相流模拟实验研究。实验采用内径为40 mm、长8 m的透明有机玻璃管,并利用高速摄像仪记录实验过程中的流型。对实验流型进行分析,发现了倾斜管中低气流速下的一种新的流型-振荡冲击流,并研究了表观气、液流速和倾斜角对气液两相流动中压降的影响,建立气/液膜流动模型来分析表观气、液流速对压降梯度的影响作用,实验研究结果表明:在高气液量范围内,倾斜管中观察到的气液两相流型主要为振荡冲击流、过渡流和环状流,并且倾角对流型转变边界的影响不显著;振荡冲击流压降随气流速的增加而降低,环状流压降随气流速的增加而增加,过渡流压降梯度最小;倾斜管压降梯度随着倾斜角度的增加而增大。     

倾斜管内热进口段自然强制复合对流传热

用数值分析方法研究了倾斜管内热进口段自然强制同向复合对流传热 ,分析了浮力、倾斜角及轴向导热对流动和传热特性的影响 ,得到了速度、温度、壁面剪切应力、局部及平均Nusselt数的分布和变化 研究结果显示Pe=71时平均Nusselt数的最大值位于 2 5°～ 45°之间 ,Pe=2 5时则在 90°处出现 .     

Velocity distributions in moving powders by microwave Doppler radar

Analysis of the Doppler signals produced by the reflections of microwaves from moving powders, using a fast Fourier transform technique, gave a power spectrum of the various frequencies, and hence velocities, present in the signal. The width of this spectrum, which is an estimate of the range of velocities present within the flowing powder, was calculated for powders of various sizes and shapes flowing on an inclined chute. The effect of particle size and shape on the spectral width produced during flow down smooth and sand-roughened chutes was investigated for angles of chute inclination between 30° and 65°. Spectral widths for flow on chutes inclined at angles well above the minimum necessary to support flow were reasonably constant down the length of the chute and were larger for flow over a sand-roughened surface than over a smooth surface. At angles close to the minimum angle to support flow, where there was a fast-moving upper layer shearing over a slower or stationary base layer, the spectral width increased considerably.     

板式换热器相变流动的传热及压降特性

建立了三维单流道模型,模拟了波纹倾角和波纹节距对相变流动传热和压降特性的影响。结果表明,沸腾传热和压降特性同时受到流动形式和触点影响,"曲折型"流动有利于液膜蒸发增强传热,触点对气相的扰动作用小于液相,因此在气相体积分数较高的区域的触点处气液相变转化现象不明显。传热系数随波纹倾角的增加而增大,随波纹节距的增加而减小,但在相同入口Reynolds数下波纹节距λ=16 mm比14 mm的传热系数大,主要是因为流动形式的改变在某种程度上减弱了触点数目减少对传热的影响。β=75°和λ=10 mm时传热性能最好。沸腾流动的压降随波纹倾角的增大先升高后降低,在β=65°左右达到峰值,随着波纹节距的增大而降低。     

Pneumatic transport of solids in an inclined geometry

Flow studies were conducted in 0.0266-m and 0.0504-m glass pipes held at various angles of inclination. Measurements in these experimental setups included particle velocities, solid mass flow rates, and pressure drops in both the upper and the lower halves of the pipe. Visual observations of the flow patterns were made through the glass section. Particles used in this system included glass particles of 67-, 450-, and 900-μm diameter, as well as iron oxide of 400-μm diameter. Mass flows from the two halves of the pipe were obtained by splitting the flow with a knife-edged separator. Experiments were also performed in a 0.0095-m transfer line in an inclined loop. The angle of inclination of the test loop was varied from 0 to 90 degrees from the horizontal. The effect of angle of loop inclination, tube diameter, and particle characteristics on basic flow parameters were studied.     

板式换热器结构优化三维数值分析

应用数值计算软件fluent对BR0.015F型人字形板式换热器进行数值模拟。分别从板片波纹的倾斜角β、高度h和间距l 3方面对板式换热器的传热、阻力影响进行研究,并拟合出相应努塞尔数Nu,传热因子j和摩擦因子f与板间流速的变化关系。结果表明:从对传热效果影响程度来看,波纹的间距l要大于倾斜角β和高度h;而对压降的影响,波纹的间距l要小于倾斜角β和高度h;从对流动状态影响程度来看,波纹夹角β和节距l要大于高度h。对比结果表明:在倾斜角β=60°,节高比为p=2.4时,板式换热器具有较好的传热效果。     

Velocities of extended bubbles in inclined tubes

The velocities of extended bubbles (slug flow bubbles) have been measured in inclined circular tubes. Eötvös numbers ranged from 4.9 to 490 and Morton numbers from 2.2 × 10⁻¹¹ to 1.5 × 10⁴. The Froude number for any angle of inclination was correlated as a function of angle and the values of the Froude numbers for the horizontal and vertical orientations.     

Experimental investigation of phosphate dust collection in impinging streams (IS)

An experimental study on collection of dry phosphate dust and coalescence of moistened phosphate dust in an Impinging-stream (IS) collector has been conducted in the presence and in the absence of a water spray. The total collection efficiency with a water spray of specific consumption of 0.3 kg water/kg dust was 95–97%. Air velocity at the inlet pipes varied between 10–30 m/s and the inclination angle with respect to the horizontal, a, of the IS was 40?60°. The water spray increased the collection efficiency by 5–20% in comparison to dry collection. In the coaxial configuration, α = 0°, it has been obtained that in the presence of a water spray, up to 55–85% of the dust accumulated on the walls of the collector, which was undesirable. Applying the inclined IS decreased the above quantities up to 5–15% with an optimal inclination angle of α = 40°. A simple model for collection of the particles has been established, showing a satisfactory agreement with experimental results.     

倾斜管内低温液弹和Taylor汽泡的长度分布

An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in an inclined tube with closed bottom by using a high speed motion analyzer.The experimental tube is 0.018 m ID and 1.0 m in length.The range of the inclination angle is 45°-90° from the horizontal.The experiment focused on the effect of the inclination angle show that the mean liquid slug length and Taylor bubble length increase with the increasing x/D at various inclination angles.At the same x/D,the mean liquid slug length and Taylor bubble length increase first,and then decrease with decreasing inclination angles,with the maximum at 60°.In the vertical tube,standard deviation of the nitrogen Taylor bubble length increase with the increasing x/D.For the inclined tube,standard deviation of the nitrogen Taylor bubble length increases first,and then decreases with the increasing x/D.Standard deviation of the liquid slug length increases with increasing x/D for all inclination angles.     

倾斜喷射时喷雾冷却无沸腾区换热特性

采用雾化角60°的半实心旋流式机械雾化喷嘴,以水为冷却介质,对流量4.44～7.05 L•h^-1,倾斜角在0°～49°之间变化时无沸腾区换热进行实验研究,并且给出了反映喷雾换热特性的量纲1换热准则公式。结果表明,倾斜角固定不变时,当喷射底面椭圆长轴与换热面相切时所对应的喷嘴高度为最佳高度,换热效果最好,冷却效率最高,其次分别是喷射底面椭圆长轴和换热面内接、外接的情况;对比不同倾斜角度、最佳高度下的换热,发现倾斜角度越大换热效果越佳,冷却效率越好。