Study on the Mass Transfer Process in Pan Wet-Spinning

2010 ◽  
Vol 650 ◽  
pp. 336-342 ◽  
Author(s):  
Bao Hua Ji
Keyword(s):  
Mass Transfer ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Bath Temperature ◽  
Solid Content ◽  
Coagulation Bath ◽  
Wet Spinning ◽  
Molecular Volume ◽  
Bath Concentration ◽  
Spun Fibers

In order to reveal the formation mechanism in PAN wet-spinning process, the Magnifying Method was used to determine the mass transfer rate difference between solvent and coagulant by measuring the weight loss percent of the spinning dope at different interval in the coagulation bath. Then the effect of coagulation condition on and on structure and properties of as-spun fibers was discussed. It was found that increased along with hoist of the molecular volume of coagulants or the coagulation bath temperature but decreased with the increase of the dope solid content or coagulation bath concentration. When the coagulation condition was very moderate（high solid content, low bath temperature or high bath concentration）, the was smaller, the counter-diffusion took place slowly and peacefully, and sequentially an even and compact meshwork microstructure was obtained, thus the density and breaking tenacity of as-spun fibers increased gradually.

Effect of Coagulation Bath Concentration on the Structure and Properties of Polyacrylonitrile as-Spun Fibers during Wet-Spinning

2011 ◽  
Vol 287-290 ◽  
pp. 1832-1836 ◽  
Author(s):  
Bao Hua Ji
Keyword(s):  
High Performance ◽  
Bath Temperature ◽  
Stretch Ratio ◽  
Shrinkage Porosity ◽  
Coagulation Bath ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Bath Concentration ◽  
Coagulation Bath Temperature ◽  
Spun Fibers

The effect of coagulation bath concentration on the structure and properties of as-spun fibers was systematically analyzed by means of X-ray diffraction, electron microprobe analysis, and the measurement of boiling-water shrinkage, porosity, and mechanical properties analysis, etc. It showed that with the increase of the coagulation bath concentration, the degree of spin orientation and the crystallinity both increased, the microstructure became compact and homogeneous, and the cross section of as-spun fibers tended to be circular. As a result, the breaking tenacity of as-spun fibers and resultant precursors both increased. Adopting the optimizing coagulation bath technique parameters: DMSO/H2O system, coagulation bath temperature 60°C, coagulation bath concentration 65%, and the minus stretch ratio –30%, the precursors and carbon fibers with high performance were prepared.

Free Convective Mass Transfer at Isosceles Triangular Surfaces of Varying Inclination

2003 ◽  
Vol 68 (11) ◽  
pp. 2080-2092 ◽  
Author(s):  
Martin Keppert ◽  
Josef Krýsa ◽  
Anthony A. Wragg
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Sulfate Solution ◽  
Convective Mass Transfer ◽  
Varying Length ◽  
Inclined Surface ◽  
Vertical Case ◽  
Limiting Diffusion Current

The limiting diffusion current technique was used for investigation of free convective mass transfer at down-pointing up-facing isosceles triangular surfaces of varying length and inclination. As the mass transfer process, copper deposition from acidified copper(II) sulfate solution was used. It was found that the mass transfer rate increases with inclination from the vertical to the horizontal position and decreases with length of inclined surface. Correlation equations for 7 angles from 0 to 90° were found. The exponent in the ShL-RaL correlation ranged from 0.247 for the vertical case, indicating laminar flow, to 0.32 for inclinations of 60 to 90°, indicating mixed or turbulent flow. The general correlation ShL = 0.358(RaL sin θ)0.30 for the RaL sin θ range from 7 × 106 to 2 × 1011 and inclination range from 15 to 90° was obtained.

scholarly journals Hydrodynamics and Mass Transfer Analysis in BioFlow® Bioreactor Systems

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1311 ◽  
Author(s):  
Marian Kordas ◽  
Maciej Konopacki ◽  
Bartłomiej Grygorcewicz ◽  
Adrian Augustyniak ◽  
Daniel Musik ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Mixing Time ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Mixing Process ◽  
Stirred Tanks ◽  
Mixing Energy ◽  
Biotechnological Processes ◽  
Liquid Transfer ◽  
Mathematical Relationships

Biotechnological processes involving the presence of microorganisms are realized by using various types of stirred tanks or laboratory-scale dual-impeller commercial bioreactor. Hydrodynamics and mass transfer rate are crucial parameters describing the functionality and efficiency of bioreactors. Both parameters strictly depend on mixing applied during bioprocesses conducted in bioreactors. Establishing optimum hydrodynamics conditions for the realized process with microorganisms maximizes the yield of desired products. Therefore, our main objective was to analyze and define the main operational hydrodynamic parameters (including flow field, power consumption, mixing time, and mixing energy) and mass transfer process (in this case, gas–liquid transfer) of two different commercial bioreactors (BioFlo® 115 and BioFlo® 415). The obtained results are allowed using mathematical relationships to describe the analyzed processes that can be used to predict the mixing process and mass transfer ratio in BioFlo® bioreactors. The proposed correlations may be applied for the design of a scaled-up or scaled-down bioreactors.

scholarly journals Mass Transfer Effects on Tracer Tests Conducted in a Heterogeneous Rock Fracture

1996 ◽  
Vol 27 (4) ◽  
pp. 215-230 ◽  
Author(s):  
Jan-Olof Selroos
Keyword(s):  
Mass Transfer ◽  
Rock Fracture ◽  
Mass Transfer Rate ◽  
Tracer Tests ◽  
Mass Transfer Process ◽  
Matrix Diffusion ◽  
Single Fracture ◽  
Experimental Conditions ◽  
Pumping Rate ◽  
Heterogeneous Rock

A methodology based on a combination of numerical simulation of conservative transport and an analytical solution for combined matrix diffusion and surface sorption is presented for the study of tracer tests conducted under non-uniform flow conditions in heterogeneous fractures. The methodology is based on a Monte Carlo technique with multiple realizations; hence uncertainty in transport estimates can be assessed. In an illustration example, the methodology is implemented for dipole pumping conditions ( i.e. one injection borehole and one retrieval borehole) in a single fracture. The effect of experimental conditions such as pumping rate and tracer properties on matrix diffusion are investigated. Due to the kinetic character of the mass transfer process, it is shown that for high flow rates with consequent high advection velocities and short residence times relative to the mass transfer rate, matrix diffusion only develops to a minor extent. The effect of fracture heterogeneity is also exemplified. The results indicate that both heterogeneity in transmissivity and matrix diffusion may be manifested as tailing in solute arrival. Hence it is generally difficult to distinguish these processes under experimental conditions.

scholarly journals The progenitors of type-Ia supernovae in semidetached binaries with red giant donors

2019 ◽  
Vol 622 ◽  
pp. A35 ◽  
Author(s):  
D. Liu ◽  
B. Wang ◽  
H. Ge ◽  
X. Chen ◽  
Z. Han
Keyword(s):  
Mass Transfer ◽  
Parameter Space ◽  
Delay Time ◽  
Mass Transfer Rate ◽  
Synthesis Method ◽  
Mass Transfer Process ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Red Giant ◽  
Ia Supernovae

Context. The companions of the exploding carbon-oxygen white dwarfs (CO WDs) that produce type-Ia supernovae (SNe Ia) have still not been conclusively identified. A red-giant (RG) star can fill this role as the mass donor of the exploding WD − this channel for producing SNe Ia has been named the symbiotic channel. However, previous studies on this channel have given a relatively low rate of SNe Ia. Aims. We aim to systematically investigate the parameter space, Galactic rates, and delay time distributions of SNe Ia arising from the symbiotic channel under a revised mass-transfer prescription. Methods. We adopted an integrated mass-transfer prescription to calculate the mass-transfer process from a RG star onto the WD. In this prescription, the mass-transfer rate varies with the local material states. First, we obtain the parameter space that leads to SNe Ia by evolving a large number of semidetached WD+RG systems with the Eggleton stellar-evolution code. Second, we investigate the Galactic rates and delay-time distributions of SNe Ia using a binary population synthesis method. Results. The parameter space of WD+RG systems that can produce SNe Ia is enlarged significantly judging by our calculations. This channel could produce SNe Ia with intermediate and old ages, contributing up to 5% of all SNe Ia in the Galaxy. Our model increases the SN Ia rate from this channel by a factor of five. We suggest that the symbiotic systems RS Oph and T CrB are strong candidates for the progenitors of SNe Ia.

Coagulation studies of cellulose/NaOH/thiourea/urea/H2O fiber spinning system

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Shuai Zhang ◽  
Fa-xue Li ◽  
Jian-yong Yu ◽  
Li-xia Gu
Keyword(s):  
Mass Transfer ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Fiber Spinning ◽  
Coagulation Bath ◽  
Coagulation Rate ◽  
Two Phase ◽  
Time Model ◽  
Rate Difference ◽  
Coagulation Process

AbstractThe coagulation properties of cellulose from cellulose//NaOH/thiourea/ urea/H2O solutions were investigated with the goal of determining the optimal coagulation conditions for the spinning of cellulose fibers. The present study was concentrated on the effect of the coagulation variables upon the coagulation process. It was observed that at the start of the process, the thickness of the solidified layer ε was proportional to the square root of time. Model experiments were performed on gelled solutions of cellulose/NaOH/thiourea/urea/H2O in a coagulation bath to determine the coagulation rate,e / t , and mass transfer rate difference between the solvent and the coagulant, Dk . The influence of coagulant compositions, coagulation time and temperature, and cellulose concentrations on coagulation rate and mass transfer rate difference performed on cellulose samples had been demonstrated by microscopic observations, which was important for understanding and controlling the process of cellulose shaping from NaOH/thiourea/urea/H2O solutions. The data were analyzed by means of the diffusion model based on Fick's law, thereby depicting the mechanism of the coagulation process, which could be described as a two-phase separation, namely a cellulose-rich phase in the coagulated layer and a cellulose-poor phase in uncoagulated layer.

Mass transfer model of supercritical fluid degradation for carbon fiber composites

2016 ◽  
Vol 51 (8) ◽  
pp. 1073-1085 ◽  
Author(s):  
Huanbo Cheng ◽  
Jie Zhang ◽  
Haihong Huang ◽  
Zhifeng Liu
Keyword(s):  
Mass Transfer ◽  
Carbon Fiber ◽  
Supercritical Fluid ◽  
Transfer Process ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Fiber Composites ◽  
Transfer Model ◽  
Carbon Fiber Composites ◽  
Mass Transfer Model

It is critical to study the mass transfer of supercritical fluid degradation for carbon fiber composites to investigate their degradation mechanism, design the reactor, and develop recycling processes. The mass transfer process of supercritical fluid degradation was described from two aspects: mass diffusion from outside to inside, and from inside to outside. Mass transfer model of supercritical fluid degradation was established based on a proposed concentric cylindrical representative volume element. The reaction kinetic parameters were incorporated into the mass transfer equation, and the concentration distribution of supercritical fluid, mass transfer rate, reaction order, and reaction rate constant during the carbon fiber composites degradation process were calculated. Relaxation time was incorporated into the mass transfer process, and the supercritical fluid concentration calculation method considering non-Fick effect was proposed. Finally, two pretreatment methods were adopted to speed up the mass transfer process.

scholarly journals Analysis of Nonlinear Dynamics for Abrupt Change of Interphase Structure in Liquid-Liquid Mass Transfer

2009 ◽  
Vol 2009 ◽  
pp. 1-13
Author(s):  
DongXiang Zhang ◽  
Min Sun ◽  
Jing Li
Keyword(s):  
Mass Transfer ◽  
Molecular Diffusion ◽  
Abrupt Change ◽  
Mass Transfer Rate ◽  
Mass Transfer Process ◽  
Liquid System ◽  
Phase Portraits ◽  
Liquid Mass ◽  
Liquid Mass Transfer ◽  
Parameter Ranges

As a liquid-liquid system is far from equilibrium state, the phase thickness is variable when mass transfer process with chemical reaction occurs in interphase zone, and a dispersible transitional layer called the interphase dispersed zone (IDZ) is formed. The IZD model composed of thermodynamically instable O/W or W/O microemulsion has reasonably explained enormous experimental phenomena in nonlinear mass transfer. To forecast the possible parameter ranges of IDZ process and abrupt change of liquid-liquid mass transfer rate, the dynamic characteristics of a molecular diffusion model are considered in this paper. We applied the bifurcation theory of planar dynamical system, Laplace transform, and maple software to investigate the model, and obtain different phase portraits of the system in different regions. The results obtained will play an important directive role in the study of IDZ model.

Simulation of volumetric heating of a moist medium with allowance for fluid mobility

2012 ◽  
Vol 9 (1) ◽  
pp. 91-93
Author(s):  
U.R. Ilyasov ◽  
A.V. Dolgushev
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Numerical Solution ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Thermal Action ◽  
Mass Transfer Process ◽  
Low Permeability ◽  
Volumetric Heating ◽  
Drying Regime

The problem of volumetric thermal action on a moist porous medium is considered. Numerical solution, the influence of fluid mobility on the dynamics of the heat and mass transfer process is analyzed. It is established that fluid mobility leads to a softer drying regime. It is shown that in low-permeability media, the fluid can be assumed to be stationary.

scholarly journals A Semi-Theoretical Model for Water Condensation: Dew Used in Conservation of Earthen Heritage Sites

Water ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 52
Author(s):  
Xiang He ◽  
Sijia Wang ◽  
Bingjian Zhang
Keyword(s):  
Mass Transfer ◽  
Theoretical Model ◽  
Field Experiments ◽  
Environmental Control ◽  
Mass Transfer Process ◽  
Formation Processes ◽  
Heritage Sites ◽  
Dew Formation ◽  
The Difference ◽  
Two Parameter

Dew is a common but important phenomenon. Though water is previously considered to be a threat to earthen heritage sites, artificial dew is showing potential in relic preservation. A model of dew prediction on earthen sites will be essential for developing preventive protection methods, but studies of dew formation processes on relics are limited. In this study, a two parameter model is proposed. It makes approximations according to the features of earthen heritage sites, assuming that a thin and steady air layer exists close to the air–solid interface. This semi-theoretical model was based on calculations of the mass transfer process in the air layer, and was validated by simulations of laboratory experiments (R > 0.9) as well as field experiments. Additionally, a numerical simulation, performed by the commercial software COMSOL, confirmed that the difference between fitting parameter δ and the thickness of assumed mass transfer field was not significant. This model will be helpful in developing automatic environmental control systems for stabilizing water and soluble salts, thus enhancing preventive protection of earthen heritage sites.

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