Devolatilization of Molten Polymers During Multiphase Flow in a Double Screw Extruder

2002 ◽  
Author(s):  
Ingo Gestring ◽  
Dieter Mewes
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Bubbly Flow ◽  
Volatile Component ◽  
Bubble Nucleation ◽  
Experimental Investigations ◽  
Complex Flow ◽  
Screw Extruder ◽  
Two Phase ◽  
Flow Mechanisms

Devolatilization is a thermal separation process in order to remove low molecular solvents from mixtures of polymers. Extruders with partly filled devolatilization zones are often used for this process. The two-phase flow of the polymer and the evaporating monomers and solvents is complex due to free surfaces. In film flow and two-phase bubbly flow the polymer is heated by dissipation and cooled by evaporation of the low molecular solvent. Temperature and concentration fields are difficult to predict in extruders because of the complex flow field. Therefore the experimental investigations are carried out in special designed apparatus with a flow field similar to that in extruders and in a transparent double-screw extruder to investigate the different flow mechanisms. In order to nucleate bubbles of the volatile component the polymers must be supersaturated and some kind of deformation must exist. The bubble nucleation is shear induced. The changes in concentration during two-phase bubbly flow result in decreasing temperatures. The mass transfer rates are increased due to the large inner surfaces of the bubbles in the foam and so is the cooling by evaporation. The higher the foam expansion the better is the mass transfer.

Research Analysis and Experiment Study on Flow Field of Hydrodynamic Coupling

2011 ◽  
Vol 418-420 ◽  
pp. 2006-2011
Author(s):  
Rui Zhang ◽  
Cheng Jian Sun ◽  
Yue Wang
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Two Phase Flow ◽  
Three Dimensional ◽  
Internal Flow ◽  
Phase Flow ◽  
Complex Flow ◽  
Two Phase ◽  
Operation Conditions ◽  
Hydrodynamic Coupling

CFD simulation and PIV test technology provide effective solution for revealing the complex flow of hydrodynamic coupling’s internal flow field. Some articles reported that the combination of CFD simulation and PIV test can be used for analyzing the internal flow field of coupling, and such analysis focuses on one-phase flow. However, most internal flow field of coupling are gas-fluid two-phase flow under the real operation conditions. In order to reflect the gas-fluid two-phase flow of coupling objectively, CFD three-dimensional numerical simulation is conducted under two typical operation conditions. In addition, modern two-dimensional PIV technology is used to test the two-phase flow. This method of combining experiments and simulation presents the characteristics of the flow field when charging ratios are different.

J056024 Mass transfer analogy in complex flow field

2011 ◽  
Vol 2011 (0) ◽  
pp. _J056024-1-_J056024-3
Author(s):  
Shintaro Shichijyo ◽  
Yoshiyuki Tsuji
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Complex Flow

scholarly journals Investigation of the combined effect of air pockets and air bubbles on fluid transients

2017 ◽  
Vol 20 (2) ◽  
pp. 376-392 ◽  
Author(s):  
Oscar Pozos-Estrada
Keyword(s):  
Bubbly Flow ◽  
Combined Effect ◽  
Hyperbolic Partial Differential Equations ◽  
Experimental Investigations ◽  
Air Bubbles ◽  
Two Phase ◽  
Pressure Transients ◽  
Air Pocket ◽  
Experimental Apparatus ◽  
Air Pockets

Abstract This paper presents numerical and experimental investigations of the combined effect on pressure transients of air pockets and homogenous water–air bubble mixtures. An air pocket can accumulate at a high point of a pipeline along the control section located at the transition between pipes with sub- and supercritical slope, forcing open channel flow conditions underneath the pocket that ends in a hydraulic jump at the downward sloping pipe. The turbulence action at the jump generates small air bubbles that are entrained and transported along the pipe producing a two-component bubbly flow within the continuous liquid phase. A numerical model is developed, combining the explicit–implicit scheme proposed by McGuire and Morris and the method of characteristics for solving the quasi-linear hyperbolic partial differential equations for transient two-phase flow expressed in conservation form. To verify the proposed model, an experimental apparatus made of PVC was used to carry out hydraulic transient experiments. Tests were conducted in a tank–pipe–valve system and a valve with a pneumatic actuator at the downstream end generated transients. Numerical results at the test section pipe compares favorably with experimental data. The results show that pressure transients are significantly reduced with increasing air-pocket volumes and bubbly flow air content.

On the Numerical Study of Bubbly Flow Created by Ventilated Cavity

2010 ◽  
Vol 29-32 ◽  
pp. 143-148
Author(s):  
Min Xiang ◽  
S.C.P. Cheung ◽  
Ji Yuan Tu ◽  
Wei Hua Zhang ◽  
Yang Fei
Keyword(s):  
Flow Field ◽  
Void Fraction ◽  
Numerical Study ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Flow Region ◽  
Valuable Insight ◽  
Two Phase ◽  
Ventilated Cavity

The aim of the study was to develop a numerical model to reproduce the bubbly flow field created by ventilated cavity which includes three different regions. The model was established based on the Eulerian-Eulerian two-fluid model coupled with a population balance approach which is solved by the Homogeneous Multiple-Size-Group (MUSIG) model to predict bubble size distribution. Base on the model, the simulation was carried out at the experimental condition of Su et al. (1995). Firstly three regions were successfully captured proved by the spatial voidage distribution and streamline shape. Then distributions of void fraction and Sauter mean bubble diameter at various sections below the cavity corresponding to three regions respectively were plotted against experimental data. A close agreement was observed in the void fraction distribution which indicates that qualitative details of the structure of the two-phase flow field below the cavity was successfully produced. The Sauter mean bubble diameter in the pipe flow region was under-predicted for about 10%. In conclusion, the proposed model was validated in predicting the multi-region flow field below the ventilated cavity which will provide a valuable insight in designing and controlling of the two phase systems with the detailed flow field information obtained.

Effects of water–air mixtures on hydraulic transients

2010 ◽  
Vol 37 (9) ◽  
pp. 1189-1200 ◽  
Author(s):  
Oscar Pozos ◽  
Alejandro Sanchez ◽  
Eduardo A. Rodal ◽  
Yuri V. Fairuzov
Keyword(s):  
Bubbly Flow ◽  
Experimental Investigations ◽  
Hydraulic Transients ◽  
Two Phase ◽  
Pressure Transients ◽  
Air Content ◽  
Air Pocket ◽  
Pressurized Pipelines ◽  
Air Pockets ◽  
The Impact

The purpose of this study is to investigate pressurized pipelines and the potential effects on pressure transients of air entrained at the downstream end of large entrapped air pockets followed by a hydraulic jump in pressurized pipelines. The homogeneous two-phase flow model is used to simulate the transient response of the bubbly mixture after a pump shutdown. The results show that pressure transients are significantly reduced with increasing air-pocket volumes and bubbly flow air content. Experimental investigations were carried out to analyze the impact of different air-pocket volumes located at high points of pressurized pipelines. A case study of an existing pumping system was considered to exemplify the impact of the bubbly flow air content on hydraulic transients.

Experimental Study on Hydrodynamic Performance of Mini-AUV in Non-Uniform Flow Field

2019 ◽  
Author(s):  
Jiayuan Zhuang ◽  
Jian Cao ◽  
Yumin Su ◽  
Lei Zhang ◽  
Xianzhao Yu
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Lateral Force ◽  
Uniform Flow ◽  
Hydrodynamic Performance ◽  
Experimental Investigations ◽  
Complex Flow ◽  
Three Dimensional Flow ◽  
Drift Angle ◽  
Current Profiler

Abstract Experimental investigations of hydrodynamic performance of mini-AUV in non-uniform flow field were conducted in the basin of Harbin Engineering University, the revolved body and flat body of mini-AUV model were tested respectively. The three dimensional flow fields were generated by local jet of the underwater pump, and circulated in the basin. The three dimensional velocity distributions at different positions were measured by a Doppler current profiler. The three component balance was used to measure the drag, lateral force and yawing moment acting on the mini-AUV models depending on drift angle in the flow field, and the influence of complex flow field to the hydrodynamic performance of mini-AUV indicated that drag was not sensitive to drift angle and yawing moment was increased obviously. The conducted experiments could supply reference to the maneuverability research of mini-AUV in real marine environments in the future.

Flow Induced Vibration of Equipment Internals in a Two-Phase Gas/Liquid Flow

2017 ◽  
Author(s):  
Philip Diwakar ◽  
Ajay Prakash ◽  
Cyrus Thomas
Keyword(s):  
Flow Field ◽  
Failure Mechanism ◽  
Liquid Flow ◽  
Structural Failure ◽  
Frequency Range ◽  
Complex Flow ◽  
Flow Induced Vibration ◽  
Two Phase ◽  
Structure Interaction ◽  
Gas Liquid Flow

The paper describes the use of Fluid-Structure-Interaction (FSI) to evaluate turning vane blades in an inlet distributor with two-phase gas/liquid flow. A fatigue failure mechanism attributed to flow induced vibration (FIV) resulting from vortex shedding and un-steadiness in the flow field is evaluated. This failure mechanism can be missed in a complex flow field that is assumed to be steady. Natural frequency of the turning vanes was found to be well within the flow induced forcing frequency range, which led to structural failure of the vanes.

scholarly journals Pore-Scale Modelling of Solvent-Based Recovery Processes

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1405
Author(s):  
Bita Bayestehparvin ◽  
S.M. Farouq Ali ◽  
Mohammad Kariznovi ◽  
Jalal Abedi
Keyword(s):  
Mass Transfer ◽  
Porous Media ◽  
Oil Recovery ◽  
Equilibrium Phase ◽  
Viscosity Reduction ◽  
Experimental Investigations ◽  
Small Scale ◽  
Pore Scale ◽  
Two Phase ◽  
Recovery Processes

A need for a reduction in energy intensity and greenhouse gas emissions of bitumen and heavy oil recovery processes has led to the invention of several methods where mass-transfer-based recovery processes in terms of cold or heated solvent injection are used to reduce bitumen viscosity rather than steam injection. Despite the extensive numerical and experimental investigations, the field results are not always aligned to what is predicted unless several history matches are done. These discrepancies can be explained by investigating the mechanisms involved in mass transfer and corresponding viscosity reduction at the pore level. A two-phase multicomponent pore-scale simulator is developed to be used for realistic porous media simulation. The simulator developed predicts the chamber front velocity and chamber propagation in agreement with 2D experimental data in the literature. The simulator is specifically used for vapor extraction (VAPEX) modelling in a 2D porous medium. It was found that the solvent cannot reach its equilibrium value everywhere in the oleic phase confirming the non-equilibrium phase behavior in VAPEX. The equilibrium assumption is found to be invalid for VAPEX processes even at a small scale. The model developed can be used for further investigation of mass transfer-based processes in porous media.

G0502 Mass transfer rate prediction in the complex flow field

2013 ◽  
Vol 2013 (0) ◽  
pp. _G0502-01_-_G0502-02_
Author(s):  
Yuki KATAI ◽  
Tatsuya TSUNEYOSHI ◽  
Taro IKAI ◽  
Teppei TANAKA ◽  
Yoshiyuki TSUJI
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Complex Flow ◽  
Rate Prediction
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