双效并流立体旋液式塔板压降的实验研究

采用全新工艺流程,设计了一种新型双效气液并流吸收塔,塔内安装有改进型立体旋液式塔板。分别以空气、空气-水作为研究体系进行实验,考察了不同操作参数与塔板结构参数下双效气液并流吸收塔的干塔压降、湿塔压降以及立体旋液式塔板的干板压降、湿板压降,明确了双效气液并流吸收塔的操作参数范围。实验结果表明:立体旋液式塔板单板干板压降及湿板压降分别控制在70 Pa,180 Pa以内。在一效、二效各逆向安装3块塔板,全塔共完全安装6块塔板时,全塔压降最大,但是干塔压降及湿塔压降可分别控制在2 400 Pa,2 800 Pa以内,双效气液并流吸收塔与立体旋液式式塔板的组合在能耗及操作弹性方面优势明显。     

摇摆对气液并流模式立体旋流筛板压降的影响研究

以空气-水为实验介质,在喷淋密度78～182 m³·(m²·h)^-1、气相动能因子1.19～2.77 m·s^-1·(kg·m^-3)^0.5、摇摆幅值Θ=5°～15°、周期T=8～20 s的条件下,测定了气液并流模式下立体旋流筛板(TRST)的压降,考察了气液通量、塔板数量、位置和方式对压降的影响,并与直立和倾斜工况对比。结果表明：增加倾斜及摇摆角度干板压降略微下降;摇摆时的湿板压降介于直立和倾斜之间,受摇摆角度影响较大,基本不受周期影响;增大气量有利于抵抗倾斜及摇摆的影响,而增大液量会使倾斜及摇摆的影响作用加剧。整体上,塔板顺、逆向安装时的湿板压降分别在100 Pa和170 Pa以内,而逆向安装的变化率约为顺向的2倍,这是由于逆向安装下改变了气液流动方向,增大了能量损失。建立了气液并流摇摆工况下TRST的湿压降预测模型,相对误差在15%以内。     

格栅穿流塔塔板压降的研究

在常温下以空气和水作为介质,对格栅穿流塔板的塔板压降进行实验研究,观察格栅穿流塔板在操作时的气液接触状态,考察了不同塔板开孔率塔板的空塔气速、喷淋密度对于干板压降、总板压降、载点气速的影响。结果表明,格栅穿流塔板的气液接触状态可以分成润湿区、鼓泡区,其中鼓泡区为合理操作区域。通过实验数据分析得到格栅穿流塔板干板压降关联式、鼓泡区格栅穿流塔板总板压降关联式和格栅穿流塔板气液负荷比与空塔气速的关联式。     

振动筛板鼓泡塔中压降的研究

本文对气—液两相流在振动筛板鼓泡塔中作垂直并流和逆流流动时的压降做了较系统的测定,并对其实验结果进行了较详细的分析与研究,结果发现逆流流动时压降比并流流动时低,而且在低ＡＦ值区域内压降波动小,有利于塔的稳定操作。     

填料塔气液并流接触时压降的研究

以内径72 mm的玻璃吸收塔为主体,分别采用Mellapack-250X型金属孔板波纹规整填料以及Dg16塑料阶梯环散堆填料作为传质媒介。以水-SO2作为研究体系,结合气液逆流接触吸收试验对比分析气液并流接触时填料层压降的情况,并分别考察了气相动能因子F和液气比L/V对填料吸收塔气液并流接触时填料层压降的影响。填料层压降随着气相动能因子F的增大呈指数型增长,随着液气比的增加而升高,并流操作时的影响相对逆流操作时变化幅度较小。通过试验结果拟合出相应压降的关联式,为进一步的工艺设计与优化提供相关依据与理论指导。     

振动片板鼓泡塔中压降的研究

本文对气－液两相流在振动筛板鼓泡塔中作垂直并和逆流流动时的压降做了较系统的测定,并对其实验结果进行了较详细的分析与研究,结果发现逆流流动时压降比并流流动时低,而且在低ＡＦ值区域内压降波动中,有利于塔的稳定操作。     

旋流塔板气液接触状态及塔板压降

旋流塔板有复杂的气液接触状态。对应于一定的气液接触现象,气液接触状态可分为倾泻区、泡花区、喷射区和全喷射区。在四种接触状态下,塔板有效压降与气速的关系有明显的差别。以有效压降随气速变化规律的转化点作为气液接触状态的转化点,确定了塔板上各种气液接触状态的区域,并关联了接触状态转化点的操作条件。对喷射区有效压降的分析得到,有效压降主要决定于塔板上液体产生的静压降,气体径向速度可以忽略,而使喷射区内有效压降不受气速影响。全喷射区内,气速影响溢流管和溢流锥的溢流能力,而使气速明显地影响塔板有效压降。泡花区内,漏液量随气速的增大而减小;因此,气速影响塔板有效压降。适当地简化流况,提出了有效压降关联式,利用实验数据确定了其中的参数。     

液体并流塔板技术进展

液体并流塔板,即相邻2层塔板上液体流动方向相同,能有效提高塔板效率。文中介绍了国内外并流塔板的板效率模型的发展状况,对国内外开发的各种并流塔板结构及性能进行了分析,并考察了立体传质塔板的性能及工业应用情况。为了开发适合大塔径的高效塔板,基于液体并流板型能提高板效率的机理,结合性能优良的立体传质塔板,采用特殊的降液结构,提出了一种新型液体并流复合塔板的结构型式。新型塔板具有气、液体处理量大、传质效率高、操作弹性大的特点,而且有效避免了普通逆流板型的液体滞留区的产生。     

倒锥型催化精馏构件的流体力学性能

为进一步提高催化精馏塔的性能,提出了一种新型倒锥型帽罩结构,针对帽罩结构参数进行实验研究。采用空气-水体系测定倒锥型塔构件不同参数下的塔板压降及液泛气速,并对其流体力学性能进行深入研究。实验结果表明,锥角对压降和液泛气速几乎没有影响。开孔比大于1时对压降无影响,开孔比小于1时压降随其值的增大而减小,液泛气速则略微增大。开孔孔径增大,则压降增大,而液泛气速减小。压降随锥体高度的增大而增大,但液泛气速与其并不呈线性变化。压降随堰高的增大而增大。催化剂装填量增大,压降增大,且液泛气速呈下降趋势。倒锥型催化精馏塔构件对其流体力学有显著影响,并在确定的条件下可选择较大的锥角,采用较小的开孔孔径和罩体高度。     

小直径管道气液逆流的流体力学

文章提出了一种新反应器形式——小通道逆流反应器,考察了模型中单管道的进出口和管长对流体力学性能的影响。设计了管道的不同进出口结构,对比研究其液泛特性。结果显示:小直径管道的进出口结构对液泛特性有明显的影响,增加管子的进出口结构使液泛气速得到极大的提高。I管的进出口形式最圆滑,可以有效避免气、液在进出口处发生冲突。其液泛气速最高可达7.6 m/s,远远高于平切口管道内的操作气速,说明进出口越圆滑液泛气速越大。使用圆滑进出口的管道,考察了管长对液泛特性的影响。发现长度增大后,管道的液泛气速相差不大,但压降有所增大。小直径管子的压降很小(100 Pa/m左右),且变化平稳。     

全混流反应器内流动规律模拟研究

研究了一种接近全混流的小型气固相反应器,可以用于在实验室研究时需要实现全混流接触状态的气固相反应的研究.采用计算流体力学软件(CFD)进行模拟得到最优结构,其结构包括1个圆锥形反应器主体,4个连接在反应器主体底部的进料口,1个连接在反应器主体上部的出料口.气体从4个进料口进入,催化剂在流动过程中从中部掉落,形成气体水平...     

基于框架设计的液流电池流场优化模拟研究

液流电池通常采用对角平推流流场,会形成电解液滞留区,造成电池局部浓差极化大,影响综合性能。鉴于此,提出了一种基于框架设计的流场优化方法,通过设计电极框架,可以得到“蛇形流道”和“平行流道”两类流场。以全钒液流电池为例,通过数学建模,研究了不同流场结构和参数对于多孔电极内电解液流动特性、电化学反应和温度变化特性的影响规律。计算结果与实验结果一致性良好,结果表明：电解液在“平行流场”内的流动均匀性比在“蛇形流场”内好,且不存在滞留区,同时在“平行流场”内浓差极化也较“蛇形流场”低;此外,对于同样的电极面积,在电极内部的“平行流道”越多,电解液的流速分布越均匀,反应特性越好。     

Measurements of flow characteristics in a confined vortex flow

A study of air flow patterns by hot-wire anemometry is reported for a vortex chamber consisting of an upper cylindrical section 122 cm in diameter and 61 cm high and a conical bottom section 122 cm high. Quantitative data are presented for flow angles, profiles of mean tangential and axial velocities, and radial distributions of tangential and axial intensities of turbulence as a function of air entrance velocities of 1.6, 2.4 and 3.2 m/s, and axial distance from the top of the chamber. In general, the quantitative results confirm the theoretical predictions and the experimental trends reported in the literature. In particular, they fully support the conclusion that the flow pattern is relatively insensitive to the entrance volumetric flow rate. A generalized correlation is presented for the axial velocity distribution. Preliminary correlations are also presented for the tangential velocity distributions in the core and in the annular region of the vortex near the wall. These were found to be functions of the axial location and of the air entrance velocity.     

Prediction of flow patterns in horizontal two-phase pipe flow

A new concept of a sequence of plots is used for the separation of flow regimes in two-phase flow. The empirical correlations themselves are based on extensive tabulations of flow-type data from the AGA-API Data Bank. Provided these data and the tabulations are accurate, the accuracy of the proposed method is better than 5%. The accuracy for any separation can easily be obtained from the information given. The probability of being able to separate flow types by the various correlations was determined and used to select the best correlations. In actual use, there will be times when a complete separation cannot be made. However, one will know this and be able to say that the flow is one of two or, rarely, more types.     

Modeling of flow dynamics in laminar aerosol flow tubes

Flow behaviour in laminar aerosol flow tubes was investigated using a Computational Fluid Dynamics (CFD) model. Since these flow tubes are typically operated at low gas velocity, even small temperature gradients produce convection currents strong enough to interfere with laminar flow. This results in recirculation, causing the residence times of aerosol particles to be poorly defined. The situation is exacerbated when temperature inversions are present, or when the flow direction and temperature are changed simultaneously. We analyzed several characteristic flow tube configurations to define the range of experimental conditions that will ensure a laminar flow profile with minimal recirculation. For a laminar flow situation, we evaluated the extent of diffusion-controlled exchange between aerosol and the flow tube wall.     

物质流、能量流与信息流协同的初探

任何一个系统（生态的、自然的、生产过程、社会的、市场的）在其内部各个环节之间及与外部环境之间都在不断地进行着物质、能量和信息的交换,在时间和空间上形成物质流、能量流和信息流.本文主要根据协同学原理,描述物质流、能量流和信息流是如何相互影响和相互依存的,并进一步指出通过对物质流、能量流与信息流协同的研究,可以实现三者之间的协调配合,以在时间和空间上形成一种最佳的有序结构.     

Melt flow instabilities in capillary flow of two-phase polymer systems

An experimental study was made of melt flow instabilities in extrusion of two-phase polymer systems. For the study, blends were prepared from two polymers: polystyrene (Dow Chemical STYRON 686) and high density polyethylene (Union Carbide DMDJ 4309). The experimental technique used in the present study was the same as that described in a previous paper by the authors. The study shows that there are abrupt increases both in exit pressure and in the recoverable shear strain (defined as the ratio of the exit pressure to shear stress) at the critical flow conditions. It has also been found that an addition of a small amount of high density polythylene (2.5 wt-% and 5.0 wt-%) increases the critical shear rate of polystyrene and hence results in a higher throughput rate before extrudate distortion is actually observed. This result is explained in terms of the independently determined melt elasticity of the two-phase systems investigated.     

Quantitative prediction of flow patterns in liquid-liquid flow in micro-capillaries

Flow patterns in microstructured reactors (or microchannels) play an important role in dictating the mass transfer rates. In the present work, experiments were carried out to investigate the two phase (liquids) flow patterns in microchannels with different cross sections and contacting geometries. The pattern formation was analysed and conditions were classified in the three regions: surface tension dominated (slug flow), transition (slug-drop and deformed interface flow) and inertia dominated region (annular or parallel flow). A criterion for liquid-liquid flow pattern transition was developed using Capillary and Reynolds numbers based on the work of Dessimoz et al. [1] for gas-liquid systems. Finally, it was applied to the literature data and good agreement was obtained. The criterion is suitable for capillaries with hydraulic diameter up to 3 mm independently of cross section form and is an important predictive tool for the rational design of micro reactors for liquid-liquid reactions.     

Hydrodynamic analysis of flow fields for redox flow battery applications

Electrolyte flow distribution is an important factor that contributes to the performance of the overall efficiency of a redox flow battery system. In the present paper, a comparative study of the hydrodynamics of the serpentine and interdigitated flow fields has been performed. Ex situ experiments were conducted using the two flow fields in conditions typical of flow battery applications. Limited in situ testing has also been conducted. These bring out the surprising result that the pressure drop in the interdigitated flow field is less than that in the serpentine for the same flow rate. Computational fluid dynamics studies show strong under-the-rib convection in the reaction zone exists in both flow fields but with a shorter residence time in case of the interdigitated. It is posited that this may explain the superior electrochemical performance of cells with interdigitated flow fields.     

平行流热管管内两相流动可视化实验研究

平行流热管换热器综合热管轴向高效换热和平行流换热器管外高效换热的优点,是一种新型的热管换热器。为了研究平行流热管工作机理及管内流动过程,搭建了平行流热管可视化实验台并对不同结构参数、不同加热功率和不同充注工质下的启动特性和传热传质规律进行了实验研究。实验结果表明：平行流热管工作机理复杂,并联管路内气柱和液柱在重力和不平衡压力的共同作用下进行互激振荡流动,并且管内出现泡状流、弹状流、环状流等多种流型,同时较高的加热功率和较大的管径会加剧工质在并联各管路之间的往复振荡,增加工质在蒸发段和冷凝段的扰动,提高热管的换热性能。