HOLDUP STRUCTURE IN HIGHLY VISCOUS NEWTONIAN AND NON-NEWTONIAN LIQUIDS IN BUBBLE COLUMNS

Gas holdup structures in highly viscous glycerine and CMC solutions are studied in a 0.305 m diameter batch bubble column. The fractional gas holdups are determined using the dynamic gas disengagement method. Empirical correlations for the gas holdup based on data covering wide ranges of viscosities in Newtonian and pseudoplastic non-Newtonian solutions are presented. For highly viscous pseudoplastic solutions in small diameter columns, the gas holdup has a square root dependence on the diameter of the column. The absence of small bubbles is suggested to be a reason for the very low volumetric mass transfer coefficients in highly viscous solutions, reported in the literature.     

水平管道气液两相流中空隙率对动态压降信号的影响

引　言在化工、石油及动力等工程中 ,气液两相流动现象极为普遍 ,其研究得到了人们的广泛重视 .气液两相流动中的管道平均压降与其他流动条件及参数之间的关系已有较多的研究 ,得到了大量数学模型和经验公式可资工程设计应用[1,2 ],但对管道压降动态特性的研究还不多见 .而对于两相流系统安全性能的设计和运行状态监控等方面 ,管道压降的动态特性无疑是极为重要的参数 .另一方面 ,气液两相流动体系中的空隙率是表示气相浓度 (含气率 )的常用指标之一 ,它对确定气液两相流系统的流型、气液分相流量以及管道中的摩擦压降、重力压降和惯性压降…     

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.     

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     

垂直同心环形管内上升气液两相环状流含气率与压降预测

对垂直同心环形管内上升气液环状流的截面含气率及压降预测进行了研究.根据Kelessidis有关团状流向环状流转换的思路以及Wallis有关圆管内环状流积分分析的方法,考虑环形管的结构特征及环状流的流型特征,通过两相动力学理论建立了新的预测截面含气率及总压降的模型.将新模型及现有模型与实验数据的分析比较表明新模型对于总压降的预测效果较好.     

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.     

气液向下并流填料塔的流型和压降

本文提供了气液向下并流填料塔内的流型转变点数据和压降数据,并对文献中提出的几个流型图和压降公式进行了验证。     

EFFECT OF MASS FLUX AND SYSTEM PRESSURE ON TWO-PHASE FRICTION MULTIPLIER

A horizontal boiling water loop was used to obtain pressure drop and heat transfer data for two-phase steam-water flow for pressures of up to 825 kPa. The data were used to examine the predictions of the separated flow model using the Lockhart-Martinelli method of estimating the two-phase friction multiplier.

The influence of mass flux on the two-phase friction multiplier has been reported for high pressure systems by many workers. The present work confirms the existence of this influence at low pressures as well. System pressure is also found to be a parameter. A correlation for the two-phase friction multiplier, incorporating the effects of mass flux and pressure, is presented here. The correlation has been tested against data from two independent sources. The predictions have been found to be in very good agreement with the data.     

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     

TWO-PHASE FLOW PRESSURE CHANGE ACROSS SUDDEN EXPANSIONS IN DUCT AREAS

A new model to calculate the two-phase flow pressure change across a sudden expansion in a duct area was developed and checked against data measured with mixtures of air and water, aqueous glycerol, watery calcium nitrate and with refrigerant R 12. In the model all relevant physical parameters are included and, in contrast to equations in the literature, the entrainment of liquid in the gas stream is considered. The predictions are validated for a wide range of conditions, pipe diameters and physical properties typically encountered in industrial pipe line systems: Calculations based on the new approach are sufficiently accurate for engineering purposes.     

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．     

PRESSURE DROP AND MASS TRANSFER COEFFICIENTS IN CONCURRENT SCREEN PLATE BUBBLE COLUMN

Pressure drop and oxygen desorption from water and four other aqueous CMC solutions were determined in a 5 cm diameter multistage bubble column with and without plate reciprocation. The plates were made from stainless steel wire screens of porosities greater than 0.62. The column pressure loss was found to increase with plate agitation, phase velocities and screen mesh number. A modified Reynolds number was proposed to permit a reasonable prediction of the pressure loss, based on the model of Noh and Baird (1984). At a specific power consumption, the present volumetric mass transfer coefficients arc considerably larger than those reported in earlier studies with sieve plates. The coefficients were correlated with specific power input, phase flow velocities and system physical properties.     

水平直圆管内油气两相流的压降

对水平放置的内径为40 mm的有机玻璃管内的油气两相流进行了详细的实验研究,实验工质为46^＃机械油和空气.油相和气相折算速度分别为0.051～0.612 m•s^-1和0.024～50.64 m•s^-1,实验在室温下进行.采用Lockhart-Martinelli关联方法对各典型流型下的实验数据进行了整理,结合流动的具体情况对其中的关联参数C进行了重新定义,提出了基于典型流型的压力梯度计算模型,并对水平管内油气两相流的压降变化规律进行了分析和讨论.理论计算值与实验测量值吻合良好.     

STATISTICAL STUDY OF CONDUCTIVITY PROBE SIGNALS: SPACE-TIME CORRELATION ANALYSIS IN ELEVATED TEMPERATURE AND PRESSURE TRANSIENT TEST FACILITY

A scaled test facility of the Babcock & Wilcox raised loop nuclear steam supply system was used to perform small break loss-of-coolant accident testing, thereby, establishing a data base from which plant predictive system codes could be benchmarked. About 250 instruments were used to record the thermal/hydraulic response of the test facility during the transient, of which 36 were conductivity probes. These probes were designed and installed to determine the liquid-steam interface in the facility hot leg, reactor core vessel, and steam generator components

Statistical behavior of the conductivity probe output signals is studied. Auto-correlation and cross-correlation analysis of nonstationary signals produced by spatially separated probes are presented. A conditional sampling technique is utilized to study the statistical behavior of the probe transient response taken over short time periods during similar events. This technique is employed since long term averaging tends to obscure some important events during a full transient study.     

混炼胶在锥形口型流动中压力降的研究

应用Ｍｏｎｓａｎｔｏ加工性能试验机，考察了天然橡胶／丁苯橡胶在锥形口型挤出过程中的流变行为。采用二阶流体本构关系和张量分析方法，导出了预测聚合物熔体在锥形口型流动中压力变化的方程式。结果表明，应用本方程式得出的入口压力降的计算值与试样的测量值有较好的一致性。     

MODELING OF THE PRESSURE DROP AND FLOW FIELD IN A ROTATING FLUIDIZED BED

Rotating fluidized beds (RFB) have found applications as dust filters, dryers, particle coaters, and granulators, and recently as catalytic reactors for the clean up of diesel exhaust. However, successful design and operation of an RFB requires an in-depth understanding of the fundamentals of the fluid dynamics involved. In this study, mechanistic models have been developed to account for the pressure drop relationship with respect to rotating speed, flow rate, properties of the granular particles, and fluidization conditions in the RFB. The models show that the total pressure drop across the bed is quadratically dependent on the rotating speed as well as the flow rate. These quadratic relationships have also been validated experimentally. The pressure drop relationship has further been validated through a full flow field numerical simulation of flow through a rotating bed with a slotted cylindrical distributor but without granular particles in the bed. Using our analytical model together with experimental results from three different types of distributors, a slotted cylinder with a thin metal screen, a perforated cylinder with a thin metal screen, and a sintered metal cylinder, three semi-empirical quadratic equations are obtained to predict the pressure drop across these distributors. A comparison of the distributor pressure drop with that across the fluidized bed (granules only) shows that the pressure drop across the distributor is appreciable and cannot be neglected in RFB applications. The higher the rotating speed, the more significant the pressure drop across the distributor.     

水平微肋管内流动蒸发换热特性的实验研究

为了研究微肋管结构尺寸及工况等对管内流动蒸发性能的影响,对4种微肋管和1根9.52 mm光管进行了实验,4根微肋管中管外径为9.52 mm和7 mm的各2根,所用工质为R22.实验中质量流速变化范围为90～400kg•m^-2•s^-1,所选工况为：蒸发温度7℃,入口干度15%～20%,出口过热度5～6℃.获得了蒸发换热性能随质量流速的变化,讨论了微肋结构尺寸和管径等对蒸发换热性能的影响.两根9.52mm微肋管的传热系数比光管分别分别提高了130%和180%,而其内表面积只比光管分别增加了40%和70%.     

COMPTON PROFILE MEASUREMENT OF TWO-PHASE FLOW DISTRIBUTION

To improve the proposed technique of Compton profile measurements and develop an accurate density distribution measurement technique, the detected scattered spectrum in a system of collimated source and uncollimated detector is expressed in terms of the density distribution and a multiple-scattering factor.

A particular experimental approach to this technique is outlined. Multiple-scattering is carefully considered in the analytical-numerical interpretation of the problem. The proposed technique is shown to be clearly valuable for stochastically steady flows in which relatively low frame rates for local time average two-phase flow parameters are acceptable.     

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.     

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.