PREDICTION OF PRESSURE DROP IN A VENTURI SCRUBBER: EFFECT OF LIQUID FILM AND RE-ENTRAINMENT

A mathematical model has been developed for prediction of pressure drop in a Venturi scrubber. This model includes the effect of the amount of liquid film and re-entrainment of liquid droplets from liquid film. The result of the present model is compared with experimental data of Viswanathan et al. (1985) as well as with the other models (Viswanathan et al., 1985; Boll, 1973). Results of this study indicate that at high liquid to gas ratios prediction of pressure drop can be improved by considering re-entrainment and liquid film effects. Also the effects of gas velocity and liquid to gas ratio were investigated on the rate of droplet re-entrainment and pressure drop.     

MODELING VENTURI SCRUBBER PERFORMANCE FOR PARTICULATE COLLECTION AND PRESSURE DROP

A computational model of gas-particle flows has been extended to predict venturi scrubber performance as measured by particle collection efficiency and pressure drop. The concept of regarding particle and liquid phases as sources of momentum and energy to the gaseous phase was incorporated into the model's computational scheme. Predicted pressure drop results showed good agreement with available experimental data, particularly when uniform liquid distribution across the venturi cross-section was achieved. Our model was also more successful in predicting particle collection efficiency than several other models previously reported in the literature. Differences between model predictions and experimental results were chiefly caused by maldistribution of injected liquid into the test scrubbers.     

高压下滴流床反应器压降和液含率的预测

采用Ａｌ－Ｄａｈｈａｎ的滴流床高压数据，确定了Ｈｏｌｕｂ详细模型中速率滑移因子ｆｖ和剪切滑移因子ｆｓ的关联式，并将简单模型和详细模型的预测与实验结果进行了比较．结果表明：在高压下详细模型的预测效果明显优于简单模型，且与实验值的偏差较小，使得Ｈｏｌｕｂ的基础模型的预测能力大大增强．     

喷嘴洗涤器洗涤效果和压降

讨论喷嘴洗涤器除尘作用和影响除尘效果的各种因素。给出喷嘴洗涤器压降的计算方法。对两种不同的设计方案进行了计算分析，反映压降与喉管、气速和洗涤液量的关系。阐明在设计和操作中应注意的问题     

THE SPLIT OF THE LIQUID PHASE IN DROPS AND FILM IN AN EJECTOR-VENTURI SCRUBBER

Liquid distribution along an ejector-Venturi scrubber was determined experimentally in an industrial-scale pilot plant. The effects of geometry as well as flow rates were studied. The results showed that a significant fraction of the liquid travels as a film. Therefore, it should be taken into consideration in mass transfer studies, where usually it is neglected. The data were used to test a model, that allows for interchange of liquid between drops and film flowing on the Venturi walls. There was good agreement between experiment and predictions.     

THE SPLIT OF THE LIQUID PHASE IN DROPS AND FILM IN AN EJECTOR-VENTURI SCRUBBER

Liquid distribution along an ejector-Venturi scrubber was determined experimentally in an industrial-scale pilot plant. The effects of geometry as well as flow rates were studied. The results showed that a significant fraction of the liquid travels as a film. Therefore, it should be taken into consideration in mass transfer studies, where usually it is neglected. The data were used to test a model, that allows for interchange of liquid between drops and film flowing on the Venturi walls. There was good agreement between experiment and predictions.     

SIMULATION OF SO2 ABSORPTION IN A VENTURI SCRUBBER

In this study, a three-dimensional mathematical model, based on a nonuniform droplet concentration distribution, has been developed to simulate gas absorption in a venturi scrubber. The mass transfer process was illustrated by assuming the liquid phase as a combination of droplets and film. The flow, just as the annular two-phase flow, includes a flow of liquid film layer on the walls and a flow of gas and liquid drops in the core. Peclet number was determined using experimental data reported by Viswanathan et al. (1984 Viswanathan , S. , Gnyp , A. W. , and St. Pierre , C. C. ( 1984 ). Examination of gas-liquid flow in a venturi scrubber , Ind. Eng. Chem. Fundam. , 23 , 303 – 308 . [Google Scholar]) for distribution of droplets across the cross section of the scrubber. The mathematical model for gas absorption was justified by comparing the theoretical predictions with the experimental data reported by Johnstone et al. (1954 Johnstone , H. F. , Feild , R. B. , and Tassler , M. C. (1954). Gas absorption and aerosol collection in a venturi atomizer, Ind. Eng. Chem. , 46, 1601–1608.[Crossref] , [Google Scholar]) and the Office of Air Programs, U.S. Environmental Protection Agency (Wen and Fan, 1975 Wen , C. Y. , and Fan , L. T. ( 1975 ). Models for Flow Systems and Chemical Reactors , 390 – 420 , Marcel Dekker , New York . [Google Scholar]), for SO₂ removal by alkaline solution and H₂O.     

滴流床式固定化植物细胞反应器中的压降和持液量

滴流床式固定化植物细胞反应器中的压降和持液量袁丽红，周名立，欧阳平凯（南京化工学院应用化学系，南京２１０００９）关键词：滴流床反应器，固定化植物细胞，压降，持液量１前言植物细胞的固定化通常采用海藻胶进行包埋，然后源源不断地提供其营养成分并通入空气，以...     

THE EFFECT OF SURFACE ROUGHNESS ON PRESSURE DROP IN A PACKED BED

Particle surface roughness is shown to have a significant effect on the pressure drop in a packed bed of adsorbent particles. The packed bed friction factor is determined using three spherical adsorbents of differing degree of surface roughness in the Reynolds number range 1-62. The results were successfully correlated using a correlation of the Ergun type. It is shown that surface roughness significantly increases the friction factor.     

低、高压滴流床中压降和持液量计算的统一关系式

基于对滴流床中气液两相流动特征尺度的分析,提出以修正的相摩擦系数对相Reynolds数进行关联,获取低、高压滴流床中压降和持液量计算的统一关联式的方法.对于滴流床中单相不饱和流（液体流动,气体静止）情形,以及低压和高压滴流床中两相流、高气液作用情形,收集了文献报道的不同大小颗粒、不同物系的大量实验数据,以相摩擦系数对相Reynolds数进行关联,得到新的压降和持液量计算式,其物理意义明确,计算精度得以提高.     

苏尔士静态混合器压降和停留时间的测定

实验测定了直径为２０～５０ｍｍ４种苏尔士静态混合器的压降，获得了摩擦因子的经验关联式，苏尔士静态混合器的压降比空管大１０～３０倍。用脉冲示踪法测定了物料的停留时间分布，发现在苏尔士静态混合器中无明显返混，可作理想柱塞流处理     

PRESSURE DROP IN FLOW OF A NEARLY CRITICAL FLUID THROUGH PACKED BEDS OF SPHERES

The flow of nearly critical carbon dioxide through packed beds of glass beads and steel spheres has been investigated. Experiments have been carried out in the intermediate range of sphere Reynolds number. Results show that around the critical point effects of fluid compressibility are negligible, and, therefore, that the friction factor can be expressed as a function of Reynolds number only. Carman [1] and Dolejs and Lecjaks [2] equations show good agreement with the experimental data.     

FLOW PATTERN AND PRESSURE DROP IN TEES

Visual observations of single and two-phase dividing flow and measurements of the gas-liquid separation behaviour, void fraction and pressure drop were performed in T-junctions having a horizontal run and vertical branch. Both tees used were geometrically similar, in scale 1:4. Plug, slug and stratified flow were observed in horizontal tubes causing mainly a total separation of the gas flow in the branch. For plug and slug flow the diverging flow pattern was stable, while for the stratified flow strong oscillations were measured. Furthermore a calculation method was developed for the prediction of the form-resistance pressure drop, based on the Gardel correlation for single-phase flow taking account of the two-phase flow pattern and the flow restriction in the tee-branch, which gives satisfactory results for all our measured data from both tees.     

颗粒流体两相流基本方程中压差力和曳力系数的计算

本文总结了颗粒流体两相流基本方程的压差力表达方式和推导颗粒流体系统曳力系数计算公式的力平衡原理，提出了一种分析压差力的简单方法，阐明了各种压差力表达方式间的关系及对应的两相流基本方程的曳力系数的计算方法     

THE EFFECT OF PARTICLE DILUTION ON WETTING EFFICIENCY AND LIQUID FILM THICKNESS IN SMALL TRICKLE BEDS

Partial wetting in small scale trickle bed reactors results in incorrect determination of intra-particle apparent kinetic parameters as well as in erroneous reactor scale-up. Although a dilution of catalyst particles with inert fines improves the catalyst wetting efficiency, it does not guarantee full external catalyst wetting at all superficial liquid mass velocities. In this work, a method is presented to relate the wetting efficiency obtained at different operating conditions and at different laboratories for diluted and non-diluted beds. Liquid film thickness in diluted and non-diluted beds is estimated. The effect of the operating conditions on partial wetting and liquid film thickness is discussed.     

快速流化床压降之研究

本文介绍了在两个不同床径的快速流化床上,用5种固体物料所进行的床层轴向压降的实验工作。并用以前所进行的φ115快速床的压降关联式为基础,对三个不同床径的压降数据进行了多元拟线性回归,得出了一个比较好地预测压降值的经验关联式。式中包括气速、固体循环量、颗粒带出速度、固、气密度比和快速床的床径等参数。预测值和实验值的平均误差为15.7%,个别点大于±20%。     

AN EXPERIMENTAL STUDY OF THE PRESSURE DROP IN FLUID FLOWS THROUGH WIRE GAUZES

Catalytic wire gauzes have been used for many years for ammonia oxidation. The flow and transfer properties of stacked gauzes, however, have not been sufficiently examined in the literature. This study presents an experimental program designed to characterize the pressure drops observed across stacked woven and knitted wire gauzes. This work generated an extensive database of measurements and reveals that each gauze requires its own correlation equation. Furthermore, previously published general models were not able to describe all four cases with high accuracy. After surveying the literature, we present some modifications to the models based on our collected experimental results.     

除油旋流器压降比的数学模型

实验研究了直径为 35mm的除油水力旋流器能量耗散与分流比的关系 .结果发现 ,当改变溢流孔径 (分别为 4、 6、 8mm)和入口流量 (分别为 30、 40、 5 0、 6 0、 70L·min^-1)时 ,只要分流比小于 2 5 % ,旋流器的能量耗散在不同入口流量下都能保持与入口流量对应的某一常数值 .当入口流量分别为 30、 40、 5 0、 6 0、 70L·min^-1时 ,旋流器的能量耗散大约分别为 10、 30、 80、 140、 2 0 5N·m·s^-1.根据旋流器的这一特征 ,并结合理论分析 ,建立了除油水力旋流器压降比数学模型 .该模型预测计算的压降比与分流比关系曲线与实验室测定的结果能很好地吻合     

PREDICTION OF ENERGY DISSIPATION IN A CONVERGENT-DIVERGENT MULTISTAGE BUBBLE COLUMN

An experimental investigation was carried out to evaluate energy dissipation of a divergent-convergent multistage bubble column (with convergent and divergent disks), which has been conceived, designed, and fabricated as a wet scrubber for air pollution control. In addition it has versatile use as a gas-liquid contactor in chemical and biochemical process industries. A detailed experimental investigation of pressure drop and energy dissipation has been reported by using a divergent-convergent multistage bubble column. Correlation developed for predicting energy dissipation has been found to be encouraging and highly significant from a statistical point of view. Energy consumption of the present system has been compared with other systems.     

TRANSFER OF HEAT AND MASS IN FALLING LIQUID FILM ON A SCREW GROOVED SURFACE TUBE

Mass and heat transfer of a falling liquid film on an external screw grooved surface of perpendicular tubes were studied and correlations by similarity parameters were obtained. The mechanism for enhancement of the transfer rate by screw grooved surface was analysed. Applying Danckwerts surface renewal model to mass transfer and heat transfer, the frequencies of renewal were evaluated and compared.