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.     

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%。     

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.     

等温气液混合器压降研究

实验研究空气-水两相流体通过等径90°T型管混合器进行混合的压降.结果表明,在实验范围内,混合后气液两相混合物的流动流型为环雾流,其压降主要与两股混合物流的动量比有关.根据混合后气液两相混合物的流动流型,模拟计算空气-水系统的压降,计算结果与实验结果较为吻合.利用该计算模型分析气液流量对混合器压降的影响.     

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     

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...     

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．     

DISCREPANCY IN THE DETERMINATION OF THE ACTIVATION ENERGY BY CATALYTIC WIRE TECHNIQUES, NH3 OXIDATION

In this work we have studied the effects of isothermal multiplicity on the determination of the activation energy in ammonia oxidation over platinum wires. By including the activity in the rate expression and following the treatment proposed by Luss et al. (1980), it was possible to unify reported data on this reaction. Experimental results show that, in the multiplicity region, the reaction rate order is zero and the characteristic activation energy is 3.4 kcal/mol.     

PERFORMANCE OF LOW PRESSURE DROP PACKINGS

The development of new dumped packings and regular packings, allowing low pressure drop per theoretical stage at high loads is necessary to achieve the demand for minimizing the energy consumption and for restricting thermal decomposition. Results of hydraulic and mass transfer investigations of some new column fillings fulfilling the afore-mentioned properties are described.     

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) Viswanathan, S., Gnyp, W. A. and Pierre, St., C. 1985. Annular flow pressure drop model for pease-Anthony-type Venturi scrubbers. AIChE. J., 31(12): 1947–1958.  [Google Scholar] as well as with the other models (Viswanathan et al., 1985 Viswanathan, S., Gnyp, W. A. and Pierre, St., C. 1985. Annular flow pressure drop model for pease-Anthony-type Venturi scrubbers. AIChE. J., 31(12): 1947–1958.  [Google Scholar]; Boll, 1973 Boll, R. H. 1973. Particle collection and pressure drop in Venturi scrubbers. Ind. Eng. Chem. Fundam., 12: 40[Crossref], [Web of Science ®] , [Google Scholar]). 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.     

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.     

管板式换热器内非牛顿流体的压降特性

分别以０．６２５％～３．４５％的羧甲基纤维素钠水溶液和粘度为０．３６１～１．８２５Ｐａ·ｓ的糖浆为实验介质，研究了流体在管板式换热器中的压降特性。为了描述流体粘度对Ｆａｎｎｉｎｇ摩擦因子的影响，在Ｆａｎｎｉｎｇ摩擦因子关联式中引入与流体粘度有关的无因次准数Ｋａ。提出了复杂结构流动通道中非牛顿流体剪切速率的求解方法，即：假定板程序在一平均剪切速率γｍ，它与几何尺寸、操作条件相同的无限大平板板间壁面的     

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     

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.     

在收缩-扩张喷嘴中气粉流的实验研究

考虑粉粒体积分率对气粉两相流的影响，作者曾经建立了收缩-扩张喷嘴中气粉流的数学模型，还采用了压强检验法，来确定喷嘴的临界截面，由此对超声速气粉流的行为作了数值计算．本文将介绍研究收缩-扩张喷嘴中气粉流行为的实验装置，并将根据实验结果与数值计算结果的对比，来验证本数学模型和压强检验法的合理性．     

液相物性对壳侧不互溶双组分两相流截面含气率及两相压降的影响

在用空气-水、空气-0号柴油研究的基础上,用空气和质量浓度为30％的甘油水溶液研究了理想管壳式换热器壳侧平均截面含气率和两相压降,以期进一步考察不同液相物性的影响.研究表明,液相物性对两者均有一定影响.提出了不同液相物性时截面含气率的通用关联式.根据流型整理了两相摩擦因子.并提出了一种新的两相摩擦压降关联式,它能较好地预测不同液相物性时两相压降的实验数据.     

气体的温度和压力及颗粒形状对固定床压降的影响

本文在Ａ－Ｓ方程的基础上推导出气体流经固定床时的压降表达式。     

EFFECTS OF AXIAL PRESSURE DROP ON THE LENGTH-AVERAGED PERMEATE FLUX IN CROSSFLOW MICROFILTRATION

A hydrodynamic model is presented which predicts the dependence of the steady-state, length-averaged permeate flux on the longitudinal pressure drop during crossflow microfiltration in both flat slit and tubular channels. The integral approach described by Romero and Davis (1988) has been extended to predict the axial variation of the transmembrane pressure drop along with that of permeate flux and cake layer thickness. The mechanism of shear-induced diffusion is employed in the analysis, which is restricted to particles with diameters of approximately 0.5-20μm (Davis, 1992), but the procedures may be extended to other particle transport mechanisms. The model predictions have been compared to the corresponding values calculated using a constant transmembrane pressure drop set equal to the arithmetic mean of those at the channel entrance and exit. The simulation results show the axial pressure drop to have the most significant effect on the average, steady-state permeate flux predictions for long, tubular channels with small critical lengths, operating under membrane resistance limited conditions and low transmembrane pressures. Neglecting the axial pressure drop, under typical operating conditions, results in as much as a 50% overestimation of the length-averaged, steady-state permeate flux.     

DRY COLUMN APPROXIMATION FOR PRESSURE DROP IN SPINNING CONE COLUMNS

A rotation-related normalization of variables has been introduced, and dimensionless fundamentally based correlations have been developed, for pressure drop in a spinning cone column (SCC) in the absence of liquid flow (dry column). The pressure drop is a sum of the dynamic and the centrifugal pressure components. Under typical SCC conditions, the correlation reduces to the form of ΔP _G  = 2N _st (k _reg R o ² + k _rot ), where N _st is a number of cone sets, Ro is the Rossby number (a rotation-normalized gas flow rate), and k _reg and k _rot are empirical coefficients characterizing the flow regime and the centrifugal efficiency of the rotor, respectively. This “dry column approximation” fits the data extremely well (the variation accounted for by the correlation is 98% of the total variation). It can be used as a theoretical limit for pressure drop prediction in an SCC at low liquid loads. The pressure regimes are classified as the centrifugal (Ro < 0.2), the intermediate (0.2 < Ro < 1.0), and the dynamic regimes (Ro > 1). Based on these dimensionless boundaries, dimensional diagrams of SCC operating regimes are constructed for laboratory and commercial-scale columns. The generality of the results is discussed in terms of the applicability of the correlations to larger scale equipment, the determination of empirical coefficients, and the linkage with CFD analysis of SCCs.     

喷动流化床流动特性研究

选用密度与尿素相近而粒度不同的三种模拟物料，在内径为１８２ｍｍ的有机玻璃喷动流化床中，对喷动流化床的流体力学行为进行了研究。测定了不同物料最大操作区所对应的静床高及喷动流化气速与床层压降、床层空隙率分布的关系。为喷动流化床尿素造粒热态试验提供了可资借鉴的设计及操作依据