Cocurrent downflow of air and water in a two‐dimensional packed column

Liquid holdup distribution in packed columns: gamma ray tomography and CFD simulation

An experimental study is conducted in a 6-in. inner diameter (ID) high-pressure facility to investigate the pressure effects on two-phase oil-gas low-liquid-loading flow in horizontal pipes. The investigated flow characteristics include pressure gradient and liquid holdup. Total of 247 tests are conducted at five different operating pressures: 200, 250, 300, 350 and 400 psig. The test fluids are nitrogen and mineral oil (Isopar-L). Superficial oil velocity ranges from 0.01 to 0.05 m/s, while superficial gas velocity ranges from 1.6 to 16.7 m/s depending on the operating pressures. Differential pressure transmitters, quick closing valves, visualization system, and dual Wire-Mesh Sensors (WMS) are used to acquire the data. The experimental data are analyzed and compared with the model predictions. Suggestions are made to improve the existing model. It is found that the operating pressure clearly affects pressure gradient. The effects of operating pressure on liquid holdup are insignificant for the investigated range. The performances of the transient multiphase-simulation software OLGA High Definition (Biberg et al. (2015)), standard OLGA version 2015 (Bendiksen et al. (1991)), the Tulsa University Fluid Flow Project (TUFFP) Unified Model version 2015 (Zhang and Sarica (2003)), and Xiao et al. (1990) models are tested against the acquired pressure gradient and liquid holdup data. The results from all models are in good agreement with experimental liquid holdup and pressure gradient data for stratified wavy flow. OLGA v2015 and TUFFP Unified Model v2015 have performed the best for annular flow. Modification of the interfacial velocity in the interfacial shear stress term in TUFFP Unified Model v2015 is suggested to partially account for the effects of the operating pressure. The new model predictions are compared with the experimental data from this study and studies from other sources. Significant improvements in the model predictions are observed in comparison with the TUFFP Unified Model v2015. Experiments at high pressures are very limited because of the high cost of these experiments. This paper provides a unique experimental data set for two-phase flow in a 6-in ID horizontal pipe at high operating pressure. In addition, the model comparison and development are given in this paper.

Analysis of flow pattern transition from segregated to slug flow in upward inclined pipes

Hydraulics and mass transfer characteristics of novel helical liquid-bridge flow structured packings

Slug liquid holdup is one of the most important parameters of slug flow. It is closely related to the average liquid holdup and pressure gradient of slug flow in wells and pipelines. Barnea and Brauner (1985) and Zhang et al. (2003a) mechanistic models are based on the turbulent nature of liquid slugs, which is typical for low viscosity oils. However, for high viscosity oil slug flow, the liquid slug is laminar due to low slug Reynolds number. In this study, a slug liquid holdup mechanistic model is developed for low and high viscosity oil slug flows. The model is based on two shear mixings including shear between the slug front and pipe wall, and shear between the slug body and liquid film. The equations are solved based on slug flow characteristics which can be calculated by solving the continuity and momentum equations of slug flow. A data bank consisting of 418 slug liquid holdup measurements is used to validate the model. In the data bank, liquid viscosity ranges from 0.0016 to 0.589 Pa·s (1.6 to 589 cP). Pipe inclination angle is from −30? to upward vertical. Pipe inner diameter (ID) varies from 5.08 to 10 cm. Statistical evaluations are also conducted against predictions of other models. Significant improvement is observed in the performance of the new model. Introduction Heavy oil constitutes a major portion of the world's total oil reserve. It is discovered and produced around the world and has become one of the most important future hydrocarbon resources with ever increasing world energy demand and depletion of conventional oils. However, heavy oil possesses very high viscosity which poses many challenges for its production and transportation. Accurate pressure gradient and liquid holdup predictions of high-viscosity oil multiphase pipe flows are imperative for heavy oil production and transportation. Most of the current multiphase flow experimental studies, correlation and model developments were conducted using low-viscosity conventional oils or other liquids. However, high-viscosity oil multiphase flow behaves very differently than low-viscosity oil multiphase flow. Significant discrepancies were observed in model comparisons. Slug flow is a dominant flow pattern in high-viscosity oil/gas pipe flow. In two-phase slug flow, liquid slugs and gas pockets propagate alternatively in the pipe. Liquid slugs without gas entrainment are rare under normal pipeline operating conditions. Instead, gas bubbles are often entrained in the liquid slugs. The liquid volume fraction in the slug body is known as the slug liquid holdup. The slugs can carry different amount of entrained gas, which primarily depends on flow rates, fluid properties, and pipe diameter. A slug unit consists of the slug body and a liquid film zone. The fast moving aerated slug body over rides the slow moving liquid film ahead of it. The slug scoops the liquid film and accelerates it to the velocity of the slug (mixture velocity). Liquid is shed from the tail of the slug to a trailing film. Slug liquid holdup is an important parameter for slug flow modeling. Most of the pressure drop in slug flow occurs in the slug body. The frictional pressure drop is greater in the slug body than in the film region. The liquid film acceleration also causes significant pressure drop in the mixing zone at the slug front. Thus the overall pressure gradient depends greatly on the slug liquid holdup and slug length.

Study on hydrodynamic performance of structured packings for gas-liquid flow: Effects of geometry parameters

Characterizing the liquid dynamics in cocurrent gas–liquid flows in porous media using twin-plane electrical capacitance tomography

Liquid flow on a vertical wire in a countercurrent gas flow

Experimental and numerical studies of detailed heat transfer and flow characteristics in the rib turbulated annulus of a double pipe heat exchanger

Water management studies in PEM fuel cells, part IV: Effects of channel surface wettability, geometry and orientation on the two-phase flow in parallel gas channels

ABSTRACTThe fine particles are considered a significant pollution problem. The wet electrostatic precipitators (ESPs) have advantages of efficient collection of the fine particles with lower pressure drop and eliminating reentrainment. The wetting properties of the collector surfaces have significantly important effect on wet ESPs’ stable and secure operation. The modified rigid collector (MRC) was modified by coating specific vinyl ester resin composites and loose glass fiber cloth over the conventional carbon steel in a certain way. The rigid collector surfaces before and after modification had been characterized by scanning electron microscopy (SEM) and interface tensiometer. The effect of operating temperatures on the wetting properties of the rigid collector surfaces before and after modification was investigated. The temperature range was 40~90 °C, and the wetting properties contained liquid holdup, surface flow rate, film rate, average film thickness, and critical saturation time. The modified rigid collector surface exhibited excellent wetting properties at the operating temperatures. The fine particles collection performance compared among the MRC, the conventional rigid collector (CRC), and the flexible collector (FC) in the wet ESPs was investigated. The effects of the applied voltage, the water film, corona power, and the specific collecting area on the fine particles collection were evaluated. The modified rigid collector provided high fine particles collection effect with lower energy and water consumption.Implications: To improve the submicron particles collection efficiency and decrease energy and water consumption, the formation of uniform water film over the collector surfaces has been widely studied. The modified rigid collector was modified by coating specific vinyl ester resin composites and loose glass fiber cloth (ERGF) over the conventional carbon steel (CCS) in a certain way. The modified rigid collector surface exhibited excellent wetting properties. The wet ESPs by the modified rigid collector exhibited significantly higher particles collection efficiency than by the conventional rigid collector.

Hydrodynamic Behaviour of Helical Rings Random Packing Using CFD Simulation

A unified hydrodynamic model is developed for predictions of flow pattern transitions, pressure gradient, liquid holdup and slug characteristics in gas-liquid pipe flow at different inclination angles from −90 to 90 deg. The model is based on the dynamics of slug flow, which shares transition boundaries with all the other flow patterns. By use of the entire film zone as the control volume, the momentum exchange between the slug body and the film zone is introduced into the momentum equations for slug flow. The equations of slug flow are used not only to calculate the slug characteristics, but also to predict transitions from slug flow to other flow patterns. Significant effort has been made to eliminate discontinuities among the closure relationships through careful selection and generalization. The flow pattern classification is also simplified according to the hydrodynamic characteristics of two-phase flow.

The Flow of Foam Films in Vertical Tubes

In this reported work, a new type of tray, a folding sieve tray (FST), consisting of duplicated perforated oblique planes folding at a specific angle was designed. A three-dimensional two-fluid CFD model was employed to predict the hydrodynamics performance of a 0.6 m FST at different folding angles (48° and 90°) and opening ratios (10.2%, 12.5%, and 15.0%), compared with a 0° unfolding-structure sieve tray (ST). The models used in this study were within the two-phase Eulerian framework to ensure that the gas and liquid phases were an interpenetrating continuum. To verify the reliability of the models, the simulation results were compared with experimental results and were found to be in good agreement, and the relative error was less than 10%. The backmixing, pressure drop, clear liquid height, froth height, entrainment and the details of the gas–liquid distributions on the tray were investigated. Better operational stability was found in FST that resulted from the better liquid distribution, a lower pressure drop across the tray, and a relatively smaller clear liquid height. It was shown that gas in the FST had a higher horizontal velocity near the holes to guide the liquid phase. About 90% of backmixing, 50% of clear liquid height, and 30%of wet tray pressure drop were reduced in the FST.