红外热像仪测量多降液管塔板液相等停留时间分布的实验研究

多降液管塔板目前在精馏、吸收和解吸等领域应用日益广泛.多降液管塔板由于降液管悬挂,且上、下塔板的降液管垂直布置,故它的液相流场分布较为复杂.提出了测试塔板上液相流场分布的一项新技术:与塔板上液体同质的高温示踪剂液体在塔板上阶跃注入,用红外热像系统拍摄高温示踪剂液体的流动,从而作出塔板上等停留时间分布图.实验在直径1200 mm的有机玻璃塔中进行,测试塔板为单根悬挂降液管塔板和两根悬挂降液管塔板,物系为空气-水.实验得到不同液量下单根和两根悬挂降液管塔板上等停留时间分布图.结果表明:该测试技术方便、精确、且示踪剂对塔内液体无干扰污染.多降液管塔板存在滞流区,且滞流区随液量增大而增大.     

倾斜塔板漏液的三维数值模拟及实验

塔体受到横向载荷作用,板式塔的塔板倾斜,塔板上液层出现非等高。在冷模试验塔装置中以空气-水为实验介质,对倾斜塔板的漏液性能进行了实验研究。实验表明,塔板倾斜方向与液相流动方向相同时,倾斜塔板漏液小于水平塔板,倾角越大漏液越少,塔板气相操作下限减小;塔板倾斜方向与液相流动方向相反时,倾斜塔板漏液大于水平塔板,倾角越大漏液越多,塔板气相操作下限增大。利用计算流体力学的双欧拉模型对倾斜塔板的漏液状态进行了三维数值模拟,模拟结果同实验结果吻合较好。模拟结果显示,倾斜塔板在液层非等高剖面上发生不均匀漏液,倾角大的塔板在液层薄的区域发生气相沟流现象。     

新垂直筛板塔的流体力学性能

在有机玻璃矩形塔和直径1.2m的圆塔上用空气-水系统研究了VST的流体力学性能.实验测定了各种几何参数和流体力学条件对塔板压降,气速上、下限和液体提升量等的影响,并从水力学的角度进行分析和讨论,获得了相应的关联式.为了降低VST的塔板阻力,研究了升气孔的形式.实验表明,圆弧形喷嘴孔VST可使塔板阻力降低40%.     

全导流95-Ⅱ型塔板上液层温度分布与板效率

引　言塔板是塔器中传质、传热最重要的元件之一 .近几十年来 ,开发大通量、高效率、低压降、低能耗的新型塔板一直是人们努力的方向 .在综合分析已有各种塔板结构性能的基础上 ,通过热力学熵增速率分析法[1] ,张志炳等开发出了 95 Ⅰ型大通量塔板[2 ] ,有关该塔板的详细介绍见文献 [3].为了进一步提高塔板效率 ,本文提出了一种全导流 95 Ⅱ型塔板结构 ,并对其进行性能实验 ,以得到板上液层的温度分布与板效率值 ,并且与 95 Ⅰ型塔板的板效率值进行了比较 .1　实验部分1 1　 95 Ⅱ型塔板结构及其全导流板的设置95 Ⅱ型塔板的平面结构如…     

筛板塔气液固三相塔板效率的实验

在冷模筛板塔上进行了气液固三相流体塔板效率的实验，得到在不同固含率下塔板气液相流量与塔板效率的变化关系. 结果表明，随着液相流量的增加，塔板效率降低；随着固含率的增加，塔板效率先增加然后减少. 并验证了气液塔板效率的计算方法可用于气液固三相塔板效率.     

固旋阀塔板液相等停留时间分布的实验研究

以空气-水为实验物系,采用温度阵列-热水示踪技术测试了固旋阀塔板上液相等停留时间分布,并研究了溢流强度和气相动能因子等因素对液相等停留时间分布的影响。实验结果表明:溢流强度和气相动能因子减小,液相停留时间会有所增加。低溢流强度下固旋阀在塔板上形成的旋转流场对塔板上液相总体流动影响较为明显,塔板上液相分布更加均匀。较大气相动能因子操作下,液相湍动能较大使液相在塔板上分布更加均匀。利用已有的模型对实验数据进行关联获得塔板上的流动参数。     

新型立体传质塔板及其流体力学性能

新型立体传质塔板（CTST）结构新颖, 充分利用塔板空间进行传质,具有通量大、效率高、压降低、抗堵性能强、消泡性能好等优点.在工业规模的实验塔上对立体传质塔板的塔板压降、帽罩底隙处罩内外压强、帽罩内部气相速度分布规律、雾沫夹带量、气体对液体的提升能力、塔板空间持液量等几个方面的流体力学性能进行了研究.结果表明,立体传质塔板克服了穿过塔板液层的阻力,板压降较低;塔板上帽罩底部的进液口处,罩内压强低于罩外,利于吸液;罩内气相速度分布比较合理;气液两相负荷均可较大幅度提高,而且雾沫夹带量非常低;气体对液体的提升性能以及塔板空间的持液性能都比较理想.     

新型导向筛板的研究

在φ600 mm的有机玻璃冷膜实验装置上,用水-空气体系对孔径为8 mm的新型导向筛板的流体力学性能进行了实验研究,测定了不同条件下的塔板压降、漏液量和雾沫夹带量等流体力学参数,对实验数据进行了关联,得出计算塔板压降、漏液、雾沫夹带的公式,可供导向筛板设计与研究使用.     

CTST-F1复合塔板的实验研究

结合CTST和F1浮阀各自的优点,在CTST塔板的基础上组合得到了新型的CTST-F1复合塔板.以空气-水为物系,在直径为570 mm的有机玻璃冷模实验塔内,对CTST-F1复合塔板的清液层高度、板压降、雾沫夹带、漏液量等流体力学性能进行了实验测定,并与CTST塔板和F1浮阀塔板的性能进行了比较.由实验数据关联得到了复...     

塔板上气泡直径的模拟计算

塔板上气液泡沫层传质面积对传质速率影响很大.传质面积由气泡的直径、大小分布和浓度所决定.气泡大小受塔板上流体力学状况影响,要对塔板上的气泡直径和分布进行可靠的模拟计算,就要对板上泡沫层的流体力学状况有着透彻了解,而板上流体力学状况十分复杂,因此,气泡直径的模拟计算和测定都很困难.气泡直径的模拟计算有两类方法--局部法和总体法.先简介局部法模拟计算气泡直径方法,然后进行总体法模拟计算气泡直径研究.通过建立一个数学模型,对塔板上泡沫层的气泡直径进行模拟计算,模拟计算结果和文献报道的实验测定结果基本一致.     

旋流板分离器的结构对三维流场的影响

引言 旋流式分离器种类很多[1-4],其中浙江大学发明的旋流板在传质和双相分离过程中均得到广泛应用[5-9].旋流板分离器是利用导向叶片使气体做旋转运动,从而产生离心力,达到气液或气固分离的目的.     

Measurements and modelling of free-surface turbulent flows induced by a magnetic stirrer in an unbaffled stirred tank reactor

Measurements and numerical simulations of turbulent flows with free-surface vortex in an unbaffled reactor agitated by a cylindrical magnetic stirrer are presented. Measurements of the three mean and fluctuating components of the velocity vector are made using a laser Doppler velocimetry in order to characterise the flow field at different speeds of the stirrer. A homogeneous Eulerian-Eulerian multiphase flow model coupled with a volume-of-fluid method for interface capturing is applied to determine the vortex shape and to compute the turbulent flow field in the reactor. Turbulence is modelled using a second-moment differential Reynolds-stress transport (RST) model, but for some cases the k-ε/k-ω based shear-stress transport (SST) model is also used. The predictions obtained using the ANSYS CFX-5.7 computational fluid dynamics code are compared with the images of the vortex and the measured distributions of mean axial, radial and tangential velocities and turbulent kinetic energy. The predicted general shape of the liquid free-surface is in good agreement with measurements, but the vortex depth is underpredicted. The overall agreement between the measured and the predicted axial and tangential velocities obtained with the RST model is good. However, the radial velocity is significantly underpredicted. Predictions of the turbulent kinetic energy yield reasonably good agreement with measurements in the bulk flow region, but discrepancy exists near the reactor wall where this quantity is underpredicted. The SST model predictions are generally of the same quality as those of the RST model, with the latter model providing better predictions of the tangential velocity distribution.     

Liquid re-circulation in turbulent vertical pipe flow behind a cylindrical bluff body and a ventilated cavity attached to a sparger

The turbulent flow field (Re=60024) in the wake of a cylindrical bluff body in a 0.105 m internal diameter pipe with an area blockage ratio of 82% in turbulent single-phase flow was studied using laser Doppler velocimetry (LDV). The results for the time-averaged velocity showed a toroidal vortex below the bluff body. The axial location below the bluff body where both the time-averaged radial and axial velocity components were zero (eye of the vortex) was found at approximately 0.72D. The end of the re-circulation region as defined by a stagnation point on the centreline of the pipe was found at an axial location below the bluff body of approximately 1.3D. These two locations did not change when altering the liquid superficial velocity confirming that the geometry (i.e., size) of the toroidal vortex is not dependent on the superficial liquid velocity or the speed of the vortex.Similar measurements using LDV were taken in the wake of a ventilated cavity in a vertical 0.105 m internal diameter pipe, with an area blockage ratio of 80%. The flow beneath the cavity was turbulent two-phase bubbly flow and the liquid-only flow ahead of the cavity was turbulent (Re=45618). The cavity was attached to a (central) sparger, which is a scale-up of the design used by Bacon (1995). The average gas void fraction in the wake of the cavity was 7%. The results for the time-averaged velocity confirmed the formation of a toroidal vortex remarkably similar to the vortex formed below the bluff body. The eye of the vortex and the end of the re-circulation region were found at an axial location below the ventilated cavity of 0.78 and 1.35D, respectively, i.e., almost identical to the results for the bluff body.The LDV results of the cylindrical bluff body and the ventilated cavity were compared with the fully predictive model of the velocity distribution in the vortex proposed by Thorpe et al. (2001) and good agreement was found in both cases. The model also agreed well with the data of van Hout et al. (2002) for a Taylor bubble rising in stagnant liquid in a 0.025 m internal diameter pipe. The CFX simulations of Thorpe et al. (2001) carried out for a 0.050 m internal diameter pipe, agreed well with the experimental data of the cylindrical bluff body, the ventilated cavity and the data obtained by van Hout et al. (2002) when correlating the results in the appropriate dimensionless form. Our analysis showed that the maximum axial re-circulation velocity in the centre of the vortex ring was directly proportional to the mean velocity in the annulus at the base of the cylindrical bluff body, the ventilated cavity or the Taylor bubble. The proportionality constant for all cases was found to be approximately 0.38 confirming the value proposed by Thorpe et al. (2001).     

非对称型外凸式波节管内的传热和流动特性

针对一种新型的非对称外凸式波节管(ACT)换热元件,基于三维RST模型对其进行了数值模拟研究。通过与传统的对称型外凸式波节管(SCT)分析比较,考察了两者流动及传热特性的区别。为了验证雷诺应力模型(RST)在研究波节管结构时的可靠性,比较了现有波纹壁面中直接数值模拟(DNS)与RST模型在同一条件下的计算结果。通过对比发现,RST模型得出的包括速度场、压力系数等计算结果与DNS所得出的结果基本吻合。随后对外凸型的流动及传热机理进行了深入探讨。结果表明,与传统的SCT相比,ACT提高综合传热性能最多能够提高32.3%。     

弯管内部油水两项流的数值模拟

在油井出油管道以及石化生产中,油水两项流是非常常见的现象。为了减少能耗、便于制订防腐措施,利用GAMBIT软件建模以及FLUENT软件的可实现模型对弯管中油水两项流的压力场和速度场进行模拟。结果表明,管内入口直管压力呈逐阶减小趋势;弯管内壁出形成低压区且又内向外逐渐增大;而速度分布正好与压力分布规律相反,恰好与自由涡流理论的模型相符。且通过对油水两项所占体积分数分别为30%、50%、80%三种情况的模拟得出,由于水密度大于油的原因,随着油相体积分数的下降,管内整体压强减小,整体速度增大。     

柱状旋流分离器零轴速面分布特性模拟分析

采用雷诺应力模型对柱状旋流分离器气相流场中的零轴速包络面分布进行了数值模拟分析,考察了旋流不稳定性、流速以及结构参数变化对其分布的影响。指出由于分离器旋转流动不稳定性的固有存在,零轴速边界在整个分离空间会呈非轴对称的扭曲状态;在研究速度范围内,流场处于自模化区,分离器运动相似,入口速度变化对零轴速边界的分布影响不大;升气管直径与入口面积对升气管入口区域的零轴速边界分布影响较大,随升气管直径的减小和入口面积的增大,零轴速边界逐渐收缩。远离升气管入口区域,升气管直径与入口面积的影响减弱,零轴速边界宽度逐渐增大,并趋于一致;使流场趋于稳定的升气管直径与入口面积,截面零轴速边界会保持较好的圆度。     

基于波理论的涡街流量计雾状流测量模型

建立了雾状流条件下涡街流量计的修正模型。雾状流中液相的存在会导致涡街流量计的测量误差,通过将以往研究者在单相流中对Karman涡街现象的认识及取得的研究成果作为基础,并结合实验流体本身所具有的动力特点,利用Karman涡街波传递的理论分析了非定常不稳定的雾状流流场中的Karman涡街现象,构建了双向耦合的气液两相流动力学模型。试验结果显示,当液相体积含率从0～0.13%变化时,模型修正后的结果与实际值较为接近。     

Test of flow field on the annular meridian plane in a tubular membrane separator with rotary tangential flow

Enhancement of membrane microfiltration by rotary tangential flow is a new technique, which is based on the hydrocyclone mechanism. It improved the structure of the general membrane separator and the form of the liquid suspension flowing into the separator, so as to increase membrane fluxes and decrease membrane fouling. In our research, a tubular membrane separator with rotary tangential flow was designed for the first time. The flow field characteristics of polypropylene tubular membrane microfiltration in this tubular separator were studied systematically by means of the Particle Image Velocimetry (PIV) test. Streamlines and velocity distributions of the meridian plane of the separator under different operating parameters were obtained. The velocity distribution characteristics of rotary circular tangential flow were analyzed quantitatively with the following conclusions being obtained:

• (1) In the non‐vortex area, no matter how the operating parameters (flux, entry pressure) change, the velocity near the rotary tangential flow entrance is higher than the velocity far from the entrance at the same radial coordinates. In the vortex area, generally the flow velocity of the inner vortex is lower than that of the outer vortex. At the vortex center, the velocity is the lowest, the radial velocity being generally equal to zero. In the vortex zone, the radial velocity is less than the axial velocity.
• (2) Under test conditions, the radial velocity and the axial velocity of the vortexes' borders are 1–2 times the average axial velocity in the annular gap of the membrane module. The maximum radial velocity and axial velocity of Taylor vortexes are 2–5 times the average axial velocity in the annular gap of the membrane module.
• (3) In the vortexes that formed on the meridian plane, it was found that mass transfer occurred between the inner and outer parts of the fluid. Much fluid moved from the outer vortexes into the inner ones, which was able to prevent particles blocking the membrane tube.

Copyright © 2004 Society of Chemical Industry     

Flow Characteristics in a Vortex Chamber

In this article we examine confined swirling flows using the integral equations of continuity and energy, along with the minimum pressure criterion. The pressure drop and the core size have been studied in the swirling confined vortex chamber. Both the n = 2 vortex model, with reverse and non‐reverse flow, and the free vortex model have been used at the vortex chamber exit plane. The influence of vortex chamber geometry, such as contraction ratio, inlet angle, area ratio, aspect ratio, and Reynolds number, on the flow field has been analyzed and compared with the present experimental data. The pressure drop across the vortex chamber differs from that in pipe flow, due to the mechanism of swirl flow that depends mainly on the intensity of tangential velocity. If the chamber length is increased, the vortex decays producing a weaker tangential velocity (less centrifugal force) that leads to less pressure drop. Based on the present theory, a new approach to determine the tangential velocity and radial pressure profiles inside the vortex chamber is developed and compared with the available experimental data. It shown that the n = 2 vortex model with reverse flow gives better results for strongly swirling flow.     

Experimental and computational study of T- and L-outlet effects in dilute riser flow

Riser outlet effects induced by an L-outlet and by abrupt T-outlets with different extension heights and outlet surface areas are studied experimentally and computationally.Experiments are carried out in a cold flow riser. The cold flow riser has a diameter of 0.1 m and a height of 8.765 m and is operated in the dilute flow regime with a superficial gas velocity of 2.48–7.43 m/s and a solids flux of 3.0 kg/m²/s. Particle velocities are measured using Laser Doppler Anemometry (LDA).Vortex formation in the extension part of the riser is observed. The vortex circulates the solids along the wall opposite to the outlet, thus inducing a solids reflux. The flow pattern upstream the outlet is, however, hardly affected in the small diameter riser. The vortex position and length are affected by the extension height, but hardly by the outlet surface area and the superficial gas velocity. The use of an L-outlet significantly reduces the vortex formation.The experimental measurements are used to validate a 3D Eulerian–Eulerian and Kinetic Theory of Granular Flow (KTGF) based gas–solid flow model. In general, the calculated trends are qualitatively in agreement with the experimentally observed phenomena. The exact shape of the vortex is not always accurately predicted.