Prediction Of Phase Separation Research Articles

Numerical investigation and prediction of phase separation in diverging T-junction

Purpose In plethora of petroleum, chemical and heat transfer applications, T-junction is often used to partially separate gas from other fluids, to reduce work burden on other separating equipment. The abundance of liquid carryovers from the T-junction side arm is the cause of production downtime in terms of frequent tripping of downstream equipment train. Literature review revealed that regular and reduced T-junctions either have high peak liquid carryovers (PLCs) or the liquid appears early in the side arm [liquid carryover threshold (LCT)]. The purpose of this study is to harvest the useful features of regular and reduced T-junction and analyze diverging T-junction having upstream and downstream pipes. Design/methodology/approach Volume of fluid as a multiphase model, available in ANSYS Fluent, was used to simulate air–water slug flow in five diverging T-junctions for eight distinct velocity ratios. PLCs and LCT were chosen as key performance indices. Findings The results indicated that T (0.5–1) and (0.8–1) performed better as low liquid carryovers and high LCT were achieved having separation efficiencies of 96% and 94.5%, respectively. These two diverging T-junctions had significantly lower PLCs and high LCT when compared to other three T-junctions. Results showed that the sudden reduction in the side arm diameter results in high liquid carryovers and lower LCT. Low water and air superficial velocities tend to have low PLC and high LCT. Research limitations/implications This study involved working fluids air and water but applies to other types of fluids as well. Practical implications The novel T-junction design introduced in this study has significantly higher LCT and lower PLC. This is an indication of higher phase separation performance as compared to other types of T-junctions. Because of lower liquid take-offs, there will be less frequent downstream equipment tripping resulting in lower maintenance costs. Empirical correlations presented in this study can predict fraction of gas and liquid in the side arm without having to repeat the experiment. Social implications Maintenance costs and production downtime can be significantly reduced with the implication of diverging T-junction design. Originality/value The presented study revealed that the diameter ratio has a significant impact on PLC and LCT. It can be concluded that novel T-junction designs, T2 and T3, achieved high phase separation; therefore, it is favorable to use in the industry. Furthermore, a few limitations in terms of diameter ratio are also discussed in detail.

Second order virial coefficients from phase diagrams

The prediction of phase separation is essential to understand and control the properties of food systems. In this work, an existing theoretical model for describing phase separation between binary mixtures of hydrocolloids, using a virial approach up to second order, is extended with several new analytical expressions. These new expressions allow one to determine the three virial coefficients directly from three characteristics of the phase diagram, where the critical point plays a pivotal role and allows one to predict the complete phase diagram. The advantage of this approach is that experimental techniques, like membrane osmometry or static light scattering, to directly measure virial coefficients can be, in principle, avoided. It was found that just the location of the critical point is sufficient to determine two of the three virial coefficients, when one of the virial coefficients is known. When, in addition to the critical point, one other characteristic of the phase diagram is known with sufficient accuracy, like the slope of the tie-lines near or far away from the critical point, all three virial coefficients can be determined from the phase diagram. Using this approach, three virial coefficients for aqueous mixtures of dextran and polyethylene oxide were determined and compared to the ones obtained from membrane osmometry.

Prediction of phase separation in a T-Junction

Despite its modest construction, T-junctions have been used as a partial phase separator in various industries for decades. To this date, the prediction of phase maldistribution at a pipe junction is a serious concern, as oftentimes very high liquid carryovers are received, affecting the operation of downstream equipment. This not only results in unforeseen maintenance, but also in the loss of operational time and cost. To address this matter, a study is reported in which experiments were conducted on five distinct diameter ratio T-junctions under stratified-wavy and slug flow conditions. From the collected data, six numerical correlations were prepared to estimate the side arm extraction of gas and liquid, as well as the pressure at main and side arm outlets of the T-junction. It was found that predictions from present equations concede reasonably well with the experimental results.

多成分系ガラスにおける分相現象の解析および同手法を利用した微細孔材創製の材料設計

多成分系ガラスにおける分相現象の解析および同手法を利用した微細孔材創製の材料設計

Characterisation and Prediction of Phase Separation in Hot-Melt Extruded Solid Dispersions: A Thermal, Microscopic and NMR Relaxometry Study

To develop novel analytical approaches for identifying both miscibility and phase separation in hot-melt extruded formulations. Felodipine-Eudragit E PO solid dispersions were prepared using hot-melt extrusion. The fresh and aged formulations were characterised using scanning electron microscopy, differential scanning calorimetry, heat capacity (C(p)) measurements using modulated temperature DSC and nuclear magnetic resonance relaxometry. The solubility of the drug in polymer was predicted as being < or =10% w/w using a novel model proposed in this study. Freshly prepared HME formulations were found to show no evidence for phase separation despite drug loadings greatly in excess of this figure. Conventional DSC showed limitations in directly detecting phase separation. However, a novel use of C(p) measurements indicated that extensive phase separation into crystalline domains was present in all aged samples, a conclusion supported by SEM studies. The NMR relaxometry study confirmed the existence of phase separation in all aged formulations and also allowed the estimation of separated domains sizes in different formulations. This study has presented a series of novel approaches for the identification, quantification and prediction of phase separation in HME formulations. Supersaturation of drug in the polymer caused the phase separation of the aged felodipine-Eudragit E PO formulations.

Prediction of phase separation in multi-component oxide glass for the fabrication of porous glass materials from waste slag

Thermodynamic analyses were performed to evaluate the composition ranges for metastable immiscibility including spinodal decomposition in multi-component silicate systems, where glass was regarded as a super-cooled liquid phase. Experimental studies on two-phase separation in glass were carried out, and the phase separation was observed in those silicate glasses corresponding to calculated metastable miscibility gaps.The authors also attempted the fabrication of porous glass using phase separation in oxide glasses containing B2O3. A multi-component borosilicate glass composition was prepared based on the silicate glass composition where spinodal decomposition had been confirmed. One of the glass phases formed by the spinodal decomposition in the boro-silicate glass was selectively removed by acid leaching and porous glass was successfully obtained.

Prediction of Phase Separation in Silicate Glass for the Creation of Value-added Materials from Waste Slag

A thermodynamic evaluation was performed to predict phase separation in multi-component oxide glasses. Composition ranges for metastable liquid–liquid immiscibility and spinodal decomposition in a SiO2–CaO–MgO–Na2O quaternary system were calculated on the assumption that glasses in the oxide system can be regarded as super-cooled liquid phases. Some experimental studies on two-phase separation of glasses were carried out to confirm the thermodynamic evaluation of the phase separation. Microstructures in heat-treated glass samples were observed by transmission electron microscopy, to investigate the development of interconnected microstructures in the glass with increased heating temperatures and holding times, and spinodal decomposition of glass was indicated.

821 細径 T 分岐管での気液二相流の相分離特性に対する既存予測モデルの適用

821 細径 T 分岐管での気液二相流の相分離特性に対する既存予測モデルの適用

Anomalous X-ray Scattering for Determination of Nanostructured Alloy Formation and Site-specific Chemistry of Bragg Peak

ABSTRACTThe properties of nanostructured films can be tailored by many factors such as composition, structure, preferred orientation, microstructure, interphase interface and grain boundaries. Compositional control of magnetic properties of recording media depends on the miscibility of constituent elements. However, for nanostructured materials with a large surface-to-volume ratio of atoms, the miscibility at the nanoscale may not necessarily follow the prediction of conventional phase diagram that does not consider the effects of surface and interface. This limitation further complicates the prediction of phase separation at grain boundaries and interphase interface. Using anomalous x-ray scattering, the alloying and composition of a specific long range order of textured nanostructured films has been investigated. Such information may not be readily available from conventional characterization techniques.

Prediction of phase separation in binary borate glasses

Binary and ternary borate glasses were melted and examined to determine the immiscibility temperature for phase separation in each system. The critical temperatures of binary borate glasses are compared to the predicted critical temperatures from the Debye-Hückel model as developed for phase separated glasses and melts. When the anion structural unit is assumed to be a BO 4 − unit with a particular interionic spacing, the results agree very well with the Debye-Hückel predictions.

Optimisation of electrical conductance measurements for the quantification and prediction of phase separation in o/w-emulsions, containing hydroxypropylmethylcelluloses as emulsifying agents

Different hydroxypropylmethylcelluloses, Methocel E and K, and one methylcellulose, Methocel A (Colorcon, Kent), were evaluated for their emulsifying properties. Eight o/w emulsions were prepared with 20%, (w/w) arachidic oil and 80% (w/w) aqueous phase containing the emulsifying agent in different concentrations. Methocel K100-LV, Methocel E50-LV and Methocel A4C were used in a 2% (w/w) concentration, while Methocel A15-LV was used in a 1, 2, 3 and 4% (w/w) concentration. The stability of the emulsions was assessed with four different techniques: visual inspection, electrical conductance, droplet size (Coulter counter) and viscosity measurements. The Methocel A15-LV 1% emulsion showed a visual instability after only 3 days, followed by the 2% emulsion (6 days) and the E50-LV (2%) emulsion (55 days). The Methocel A15-LV 3 and 4%, the Methocel K100-LV (2%) emulsion and the A4C (2%) emulsion showed no visual instability after 90 days. For all emulsions, the difference in electrical conductance between the upper and lower part of the conductance cell, especially designed for the stability study, gradually increased with ageing. Droplet size measurements showed no major differences in droplet size as a function of time, probably due to the fact that before measurements the emulsions had to be gently shaken before sample taking. The conclusion of this study is that the electrical conductance measurements in the specially designed cells can be used to quantify and predict the phase separation in o/w-emulsions.

Optimalisation of electrical conductance measurements for the quantification and prediction of phase separation in O/W-emulsions containing hydropropylmethylcelluloses as emulsifying agents

Optimalisation of electrical conductance measurements for the quantification and prediction of phase separation in O/W-emulsions containing hydropropylmethylcelluloses as emulsifying agents

Theoretical aspects of self-stratification

In order to predict whether a system of two polymers or resins in a common solvent mixture will ‘self-stratify’, two predictive models, one based on UNIFAC and the other on surface tension relationships, have been developed. The UNIFAC model can predict phase behaviour, vapour pressure, evaporation rates and surface tensions for systems containing two polymers or resins in a solvent mixture. Comparisons between experimental and calculated data are made for acrylic/acrylic, epoxn/acrylic and alkyd/acrylic resin combinations. The prediction of phase separation during solvent evaporation from a thin film is satisfactory in most cases, especially when the difference in molecular weight between the two polymers is not too large. For epoxy/acrylic resin combinations, the calculated evaporation profiles are in reasonable agreement with observed values. The evaporation rate decreases with increasing epoxy molecular weight, but is almost independent of the acrylic resin and the resin ratio. The tendency of epoxy/acrylic resin combinations to undergo self stratification is predicted to increase as the molecular weight of the epoxy resin increases. The degree of phase separation is increased as the molecular weight of the acrylic resin is increased. These predictions agree with experimental observation but for acrylic/alkyd resin combinations, no phase separation is predicted which is not in agreement with experiment. This is probably because the model cannot allow for the broad molecular weight distribution of the alkyd resin. A second predictive model based on surface energy variation with concentration of two polymer solution phases in contact has been developed. This model can be used to predict which resin combinations will give rise to self-stratifying systems given the surface energy/concentration relationship of the pure resins in solution and assuming the systems have phase separated. For solutions of epoxy resins combined with a second resin the model correctly predicts the observed tendency for the resins to stratify provided the system phase separates at some point.

Prediction of Phase Separation During the Drying of Polymer Shells

During the drying of polymer shells formed by microencapsulation, vacuole formation is believed to occur as a result of phase separation. To better understand and control this process, we have used a multicomponent diffusion formalism to predict compositional changes in the layer as organic solvents diffuse out and water diffuses into the layer. Formation of thermodynamically unstable compositions can lead to phase separation by condensation of water on submicron foreign particles present in the shell wall. We used statistical mechanics, the UNIFAP methodology, and empirical data to deduce the required values of transport coefficients and equilibrium phase compositions. The results suggest that vacuole formation can be eliminated or reduced by removing submicron and larger particles from the shell wall and by using solvents with lower intrinsic water solubilities. 21 refs., 7 figs.