Phase Mass Transfer Research Articles

Simulation and Experimental Study on Metal Microstructure of Meniscus‐Confined Electrodeposition

Meniscus‐confined electrodeposition (MCED), as one of the multifunctional additive manufacturing methods for microsensor manufacturing and flexible electrical interconnection, has great potential in future miniaturized communication devices. At present, however, the understanding of the multiphysical field processes involved in this method, such as electrodeposition, fluid dynamics, and mass and heat transfer, is limited, and the deposition forming process has not yet been well explained. Herein, the manufacturing process of metal microstructure used by MCED is studied, and the contour features of the microstructure are characterized. Simultaneously, based on the law of liquid phase mass transfer in microzone, the theoretical model of MCED process is established, the important role of Marangoni effect in evaporation process is revealed, and the effect of evaporation process on MCED is analyzed and discussed. Besides, the effect of evaporation process on the dynamic process of deposition is further proved by simulation analysis. The additive manufacturing equipment based on MCED is built to manufacture metal microstructure. Furthermore, the effects of evaporation on the morphology, roundness, vertical angle, and chemical composition of deposited metal microstructure are analyzed experimentally. These results provide a promising platform for the direct fabrication of nanocircuit interconnections, microsensors, and microantennas.

Radio Nebulae from Hyperaccreting X-Ray Binaries as Common-envelope Precursors and Persistent Counterparts of Fast Radio Bursts

Roche lobe overflow from a donor star onto a black hole or neutron star binary companion can evolve to a phase of unstable runaway mass transfer, lasting as short as hundreds of orbits (≲102 yr for a giant donor) and eventually culminating in a common-envelope event. The highly super-Eddington accretion rates achieved during this brief phase ( are accompanied by intense mass loss in disk winds, analogous to but even more extreme than ultraluminous X-ray (ULX) sources in the nearby universe. Also in analogy with the observed ULX, this expanding outflow will inflate an energetic “bubble” of plasma into the circumbinary medium. Embedded within this bubble is a nebula of relativistic electrons heated at the termination shock of the faster v ≳ 0.1c wind/jet from the inner accretion flow. We present a time-dependent, one-zone model for the synchrotron radio emission and other observable properties of such ULX “hypernebulae.” If ULX jets are sources of repeating fast radio bursts (FRB), as recently proposed, such hypernebulae could generate persistent radio emission and contribute large and time-variable rotation measure to the bursts, consistent with those seen from FRB 20121102 and FRB 20190520B. ULX hypernebulae can be discovered independently of an FRB association in radio surveys, such as VLASS, as off-nuclear point sources whose fluxes can evolve significantly on timescales as short as years, possibly presaging energetic transients from common-envelope mergers.

Effect of fluid properties and boundary conditions on rod pump efficiency – Novel modeling

Among artificial lift systems, the most widely used method is sucker rod pumping. Since its inception in the oil industry, inefficiency in sucker rod pumping system due to gas interference is one of major concerns. The need for better understanding of gas interference during sucker rod pumping process is significantly required. Although, many models and techniques are available but there are many parameters, which need to be well studied and adequately addressed. This delineates the need to research all empirical parameters that could affect efficiency of conventional rod pump. The pump performance appears to be low in presence of gas which in extreme situation locks the pump and make the pump paralyzed completely. The models available in literature neglect mass transfer during suction process, which brings unreliable calculation of gas phase in pump. Models in literature on efficiency of pump and gas lock are studied to analyze the vital parameters and reasons for the inefficiency. The expedient analytical models to predict gas lock criteria and efficiency of conventional pump, based on liberation of gas during pumping, are established in this work. The models emphasize the importance of the fluids properties to be handled by pump, which affect the production rate while pumping with a gaseous phase. This new model considers free gas phase presence and mass transfer during working of pump. Sensitivity and comparative analysis of numerous parameters contributing to pump efficiency is established in this work. The study results provide some theoretical and analytical references for further advancements in system efficiency of conventional rod pump system and to improve economic benefits.

Tidal Wave Breaking in the Eccentric Lead-in to Mass Transfer and Common Envelope Phases

The evolution of many close binary and multiple star systems is defined by phases of mass exchange and interaction. As these systems evolve into contact, tidal dissipation is not always sufficient to bring them into circular, synchronous orbits. In these cases, encounters of increasing strength occur while the orbit remains eccentric. This paper focuses on the outcomes of close tidal passages in eccentric orbits. Close eccentric passages excite dynamical oscillations about the stars’ equilibrium configurations. These tidal oscillations arise from the transfer of orbital energy into oscillation mode energy. When these oscillations reach sufficient amplitude, they break near the stellar surface. The surface wave-breaking layer forms a shock-heated atmosphere that surrounds the object. The continuing oscillations in the star’s interior launch shocks that dissipate into the atmosphere, damping the tidal oscillations. We show that the rapid, nonlinear dissipation associated with the wave breaking of fundamental oscillation modes therefore comes with coupled mass loss to the wave-breaking atmosphere. The mass ratio is an important characteristic that defines the relative importance of mass loss and energy dissipation and therefore determines the fate of systems evolving under the influence of nonlinear dissipation. The outcome can be rapid tidal circularization (q ≪ 1) or runaway mass exchange (q ≫ 1).

Multi objective optimization of the amines- CO2 capture absorption-desorption process by a non-equilibrium rate model

The global concentration of CO2 in the atmosphere is increasing rapidly. CO2 emissions have an impact on global climate change. Carbon dioxide capture technologies have been proposed as a promising alternative to reducing CO2 emissions from fossil fuel power plants with post-combustion capture. Amine-based chemical absorption is considered the most industrially developed technology for this kind of process. In this work, a strategy for defining the relationships between design and the operational policies in CO2 capture technologies is addressed. The solution to the problem consists in maximizing the percentage of the CO2 removal, while the stripper reboiler duty is minimized. Since both objective functions in conflict, a multi-objective optimization approach is proposed to achieve a trade-off. Moreover, due to the highly non-ideal behavior in the heat and mass transfer phase, a fully rigorous model was used to capture this strongly non-linear behavior. In addition, an economic evaluation of the heating and cooling utilities in the stripper according to the operation process is carried out. The results show the importance of considering the significance between the influence of operating variables (i.e., temperature, liquid solvent flow rate, and operating pressure) on the amount of CO2 removed and the associated reboiler duty. It shows that both optimal operating policies can be traded-off. Finally, with 30 wt% of MEA solvent, the compromise solution presents a 77% CO2 capture with an energy consumption of 4.98 GJ/t of CO2 for the reboiler service, a cost of heat utilities per year of $3971 capturing 142.29 kg/h of CO2.

Evolution of AM CVn Binaries with White Dwarf Donors

The evolution and the stability of mass transfer of CO+He white dwarf (WD) binaries are not well understood. Observationally they may emerge as AM CVn binaries and are important gravitational wave (GW) emitters. In this work, we have modeled the evolution of double WD binaries with accretor masses of 0.50–1.30 M ⊙ and donor masses of 0.17–0.45 M ⊙ using the detailed stellar evolution code mesa. We find that the evolution of binaries with same donor masses but different accretor masses is very similar and binaries with same accretor masses but larger He donor masses have larger maximum mass transfer rates and smaller minimum orbital periods. We also demonstrate that the GW signal from AM CVn binaries can be detected by spaceborne GW observatories, such as LISA and TianQin. There is a linear relation between the donor mass and gravitational wave frequency during the mass transfer phase. In our calculation, all binaries can have dynamically stable mass transfer, which is very different from previous studies. The threshold donor mass of Eddington-limited mass transfer for a given accretor WD mass is lower than previous studies. Assuming that a binary may enter a common envelope if the mass transfer rate exceeds the maximum stable burning rate of He, we provide a new criterion for double WDs surviving mass transfer, which is below the threshold of the Eddington limit. Finally, we find that some systems with oxygen–neon (ONe) WDs in our calculation may evolve into detached binaries consisting of neutron stars and extremely low-mass He WDs, and further ultracompact X-ray binaries.

A molecular dynamic simulation on the memory effect of methane hydrate

The memory effect is one of the outstanding mysteries to be solved in the field of clathrate hydrates. In this study, a thaw-freeze cycle simulation tracing the evolution of residual hydrate cages was conducted in line with hydrate recrystallization in experiments. It has been demonstrated that the hydrate dissociates layer-by-layer parallel to the exposed surface of the hydrate phase inwards in three steps with different decomposition rates, i.e., firstly, hydrate rapidly decomposes due to its exposure to gas ambience. Secondly, an additional liquid phase mass transfer resistance is introduced for decomposing CH4 molecules into gas phase due to the water reservoirs emerged by decomposition of external hydrate, resulting in a decomposition stable stage until the hydrate phase vanished. Thirdly, gas-liquid two-phase completes separation. The critical nucleus size has been identified as a criterion to explicate the memory effect. The decreasing residual nuclei with increasing temperature and time during dissociation prolong the induction time. These findings can help to better understand the memory effect at the molecular scale.

Theoretical and Experimental Models to Evaluate the Possibility of Corrosion Resistant Concrete for Coastal Offshore Structures.

This study built theoretical and practical models to evaluate the corrosion resistance of concrete for coastal offshore structures in Vietnam. A mathematical model was developed in the form of a system of nonlinear partial differential equations characterizing the diffusion “free calcium hydroxide” in a solid of a concrete structure. The model describes the process of non-stationary mass conductivity observed in the “concrete structure—marine environment” system under non-uniform arbitrary initial conditions, as well as combined boundary conditions of the second and third kind, taking into account the nonlinear nature of the coefficients of mass conductivity k and mass transfer β. It was shown that the solution of the boundary value problem of non-stationary mass conductivity allows us to conclude about the duration of the service life of a concrete structure, which will be determined by the processes occurring at the interface: in concrete—mass conductivity, depending on the structural and mechanical characteristics of hydraulic structures, and in the liquid phase—mass transfer, determined by the conditions of interaction at the interface of the indicated phases.

Evolution behaviour of interfacial structure between quicklime and converter slag: slag-forming route based on FetO component

ABSTRACT In order to enable the steel companies to achieve carbon peaks and carbon neutrality, the f-CaO content in steel slag should be reduced. For this reason, this study investigates the interface reaction evolution of the quicklime and different slag in the ‘iron’ slagging route of the CaO-FetO-SiO2-MgO system at the converter steelmaking temperature. The microstructure of the reaction interface was observed by an electron microscope. The results showed that the interface reaction formed CaO-FeO solid solution, (Ca, Mg) olivine phase, and 2CaO·SiO2. The change in thickness of CaO-FeO and (Ca, Mg) olivine shows a clear trend with the change in slag components.Therefore, the dissolution mechanism of quicklime in the slag was discussed, and the liquid phase mass transfer coefficients in different slags were obtained. The results will provide a theoretical basis for the faster dissolution of lime in slag and reduction of f-CaO content in slag.

Three-Dimensional Open Water Microchannel Transpiration Mimetics.

The key problem that hinders the water transportation performance and application of microchannels is the annoying gaslock. Realizing liquid transport without the gaslock requires a specially designed pump and a channel system, as well as the reduction of gas concentration in liquids. In nature, to eat viscous nectar with high efficiency, hummingbirds use their open geometric tongue for nectar-sucking. Inspired by hummingbirds' tongue, we report a bionic open microchannel that discharges unwanted gas inside the microchannel from the opening without influencing its fluidic performance. The opening can also be used for extrusion of oil droplets in microchannels, indicating great potential applications in oil-water separation and chemical slow release, especially for bubble discharge in microchannels. Most significantly, a mimicked "leaf" with our bionic open microchannnels exhibits marvelous "transpiration" performance when irradiated by a laser. Our work provides a new strategy for the fabrication of open microchannels and sheds light on potential applications of multiphase phenomena in microchannels including oil-water separation, phase change heat and mass transfer, solar vapor generation, and precisely controllable drug delivery.

Nitrogen Solubility and Gas Nitriding Kinetics in Fe–Cr–Mo–C Alloy Melts under Pressurized Atmosphere

The precise control of nitrogen content in high nitrogen martensitic stainless steel is the guarantee of its excellent performance, and is a crucial issue for its manufacturing process using pressurized gas nitriding. In this paper, the effects of nitrogen pressure, temperature and alloy composition on nitrogen solubility and pressurized gas nitriding kinetics of Fe–Cr–Mo–C alloy melts were investigated. In order to correct the deviation of nitrogen solubility from Sieverts’ law under high nitrogen pressure, the first- and second-order interaction parameters of nitrogen on itself were obtained; accordingly, the nitrogen solubility model under pressure was established and well verified. The nitrogen solubility decreased with increasing temperature and C content, and increased with increasing Cr and Mo contents. The nitrogen mass transfer in liquid phase was the nitriding rate-determining step under different nitrogen pressures. The apparent mass transfer coefficient of nitrogen was approximately 0.0218 to 0.0230 cm·s−1, and showed a weak dependence with pressure. The apparent mass transfer coefficient of nitrogen increased significantly with the increase of temperature and electromagnetic stirring, and was rarely affected by the content of Cr, Mo and C. Considering the influence of pressure change on nitriding rate in pressurization stage, a novel kinetic model for gas nitriding under high pressure was established and exhibited effectiveness in practice.

3D Hydrodynamical Simulations of Helium-ignited Double-degenerate White Dwarf Mergers

The origins of Type Ia supernovae (SNe Ia) are still debated. Some of the leading scenarios involve a double detonation in double white dwarf (WD) systems. In these scenarios, helium shell detonation occurs on top of a carbon-oxygen (CO) WD, which then drives the detonation of the CO core, producing an SN Ia. Extensive studies have been done on the possibility of a double helium detonation, following a dynamical helium mass-transfer phase onto a CO-WD. However, 3D self-consistent modeling of the double-WD system, the mass transfer, and the helium shell detonation have been little studied. Here we use 3D hydrodynamical simulations to explore this case in which a helium detonation occurs near the point of Roche lobe overflow of the donor WD and may lead to an SN Ia through the dynamically driven double-degenerate double-detonation (D6) mechanism. We find that the helium layer of the accreting primary WD does undergo a detonation, while the underlying CO core does not, leading to an extremely rapid and faint nova-like transient instead of a luminous SN Ia event. This failed core detonation suggests that D6 SNe Ia may be restricted to the most massive CO primary WDs. We highlight the nucleosynthesis of the long-lived radioisotope 44Ti during explosive helium burning, which may serve as a hallmark both of successful as well as failed D6 events, which subsequently detonate as classical double-degenerate mergers.

Vibration-induced enhanced mass transfer within membrane contactors for efficient CO2 capture

Membrane gas-solvent contactors are a hybrid separation technology that has significant potential to replace conventional solvent columns in a range of industrial applications. One industry application where the technology has shown promise is for carbon dioxide capture. The performance of membrane gas-solvent contactors is limited by the mass transfer resistance on chemical species traversing from the gas to the solvent phases, with the boundary layer of the solvent phase representing the rate limiting stage. Here, enhancements to mass transfer were achieved by applying vibration to the membrane module. An increase in the overall liquid phase mass transfer coefficient (KL) was associated with both the frequency and amplitude of the vibration. A vibration amplitude displacement between 0 and 16% resulted in overall mass transfer being 10 to 21% higher than the non-vibrational case. Similarly, a vibrational frequency of 2.3 Hz corresponded to mass transfer enhancement of up to 20% higher than the non-vibrational case. This represents a significant improvement in the membrane contactor’s mass transfer performance for carbon dioxide separation. To quantify vibration improvement in membrane contactors, a mass transfer correlation for the solvent phase of the membrane contactor system was established, based on a vibrational dimensionless number. This correlation enabled the performance of membrane contactors under vibration conditions to be model and provide insight into the vibrational conditions that will enhance mass transfer. Subsequently, an analysis of the power requirement for module vibration was undertaken to demonstrate the most effective applications of vibrations.

Nitrox surface discharge used for water activation: the reactive species and their correlation to the bactericidal effect

Plasma activated water (PAW) is a promising green antibacterial agent and the bactericidal effect is complicatedly affected by electron bombardment, ultraviolet radiation, interface reaction, and cascade chemical reaction. In this paper, a case of preparing PAW by treating aqueous solutions with afterglow gas is constructed based on surface micro-discharge (SMD), which focuses on the effect of afterglow gas–liquid mass transfer and liquid phase chemistry on PAW sterilization. The correlation of the bactericidal effect of PAW to the reactive species was studied based on the model of methicillin-resistant Staphylococcus aureus. The production of reactive oxygen and nitrogen species (RONS) in PAW with the regulation of N2/O2 ratios in the working gas for SMD. The RONS in both gas and liquid phases and the physicochemical properties of PAW were measured through optical and chemical methods. In addition, the effects of liquid types, liquid conductivity, and storage time on the bactericidal effects of PAW were explored. The key species for bacteria inactivation were identified by equivalent mixed solutions and specific scavengers. The results demonstrated that control of the N2/O2 ratios in the working gas can effectively improve the RONS in plasma and PAW. The bactericidal effect of PAW is correlated with peroxynitrite, superoxide anion, and their synergistic effects in an acidic liquid environment. This study provides a new strategy for insight into the bactericidal mechanism of PAW in biomedical applications.

Intensified biogas upgrading via various wastewater using microchannel

In this article, several ideas have been proposed for CO2 separation and biogas upgrading using industrial wastewater. Synthetic gas (60% CH4, 40% CO2) has been upgrading in atmospheric pressure in a T-shaped microchannel using municipal, meat processing, water distillation, dairy, caustic, and fish pond wastewater. The municipal, fish pond, and meat processing wastewater contain ammonia, while dairy, and water distillation wastewater contains Ca2+, and Mg2+. Also, the caustic refinery wastewater contains NaOH, with higher alkalinity for CO2 separation. The effect of temperature, gas, and liquid flow rate were investigated. RSM analysis provided a function of three dependent variables of quadratic model for prediction of responses (CO2 removal efficiency and total mass transfer in gas phase) by each absorbent, and all models were meaningful. In addition, given that all R2 values were greater than 0.94, it was indicated that experimental values for removal of CO2 and mass transfer coefficient are favorably consistent with the values of the model. Maximum CO2 absorption was obtained at 30°C, liquid flow rate of 150 mL/hr, and biogas flow rate of 50 mL/min. According to the results obtained for mass transfer coefficient, these coefficients are at least 5 to 22 times greater than mass transfer coefficient in chemical absorption in normal absorption towers, such as packed towers.

Desulfurization behavior of Si-killed 316L stainless steel melt by CaO-SiO2-CaF2-Al2O3-MgO slag

The desulfurization behavior of 316L stainless steel (STS316L) melt with the CaO-SiO2-CaF2-Al2O3-MgO slag was investigated with different CaO/SiO2 (=C/S) ratio and CaF2 content at 1873 K. As the C/S ratio increased, the sulfide capacity increased, whereas the sulfide capacity of the high C/S (=1.7) slag was not affected by CaF2 content. The overall mass transfer coefficient (kO) increased with C/S ratio, but was constant above a critical C/S value, and it was also constant across varied CaF2 content at relatively high C/S (=1.7) condition. Since the metal condition of the present study was constant, the change in kO was caused by slag phase mass transfer coefficient (ks) and sulfur distribution ratio (LS), which were affected by the physicochemical properties of the slag. Since desulfurization reaction requires consideration of both kinetic and thermodynamic factors, the ‘logCS2−−logη’ (where CS2− is sulfide capacity and η is viscosity), was proposed as a meaningful physicochemical parameter. If the slag basicity is relatively high, at which the kO is equivalent regardless of slag compositions, the desulfurization reaction is controlled by metal phase mass transfer. However, if the slag basicity becomes lower, at which the kO significantly decreases, the desulfurization reaction is assumed to be controlled by slag phase mass transfer and/or mixed controlled process.

Concentration and temperature measurements by means of Raman spectroscopy in case of condensation with non-condensable gas

Abstract Condensation in presence of non-condensable gas is safety relevant in case of loss-of-coolant accidents in pressurised water reactors. Non-condensable gas reduces the heat and mass transfer in the vapour phase, especially with low steam velocities. Insufficient heated emergency core cooling water can cause thermal shocks at the reactor pressure vessel for example. Within the scope of a research project supported by the Bundesministerium für Wirtschaft (BMWI) experiments have been performed to study the effect of non condensable gases on direct contact condensation at horizontal stratified steam/water flow. The paper presents the laser-optical measurement technique linear Raman spectroscopy for determination of concentration profiles in the vapour phase and temperature profiles in the liquid phase with high local resolution. The film theory, described in this paper, allows the approximation of these measured concentration profiles and therefore the calculation of local heat and mass transfer. If homogenous condensation occurs, the fog density in the vapour phase can also be estimated by means of Raman spectroscopy. Steady state and transient experiments are presented.

Planet Hunters TESS IV: a massive, compact hierarchical triple star system TIC 470710327

ABSTRACTWe report the discovery and analysis of a massive, compact, hierarchical triple system (TIC 470710327) initially identified by citizen scientists in data obtained by NASA’s Transiting Exoplanet Survey Satellite (TESS). Spectroscopic follow-up observations obtained with the hermes spectrograph, combined with eclipse-timing variations (ETVs), confirm that the system is comprised of three OB stars, with a compact 1.10 d eclipsing binary and a non-eclipsing tertiary on a 52.04 d orbit. Dynamical modelling of the system (from radial velocity and ETVs) reveal a rare configuration wherein the tertiary star (O9.5-B0.5V; 14–17 M⊙) is more massive than the combined mass of the inner binary (10.9–13.2 M⊙). Given the high mass of the tertiary, we predict that this system will undergo multiple phases of mass transfer in the future, and likely end up as a double neutron star gravitational wave progenitor or an exotic Thorne–Żytkow object. Further observational characterization of this system promises constraints on both formation scenarios of massive stars as well as their exotic evolutionary end-products.

Microstructure and mechanical properties of (Ti,W)C cermets prepared by ultrafast spark plasma sintering

To explore the impact of the sintering rate on the microstructure and mechanical properties of cermets, the preparation of (Ti,W)C cermets by ultrafast sintering via spark plasma sintering (SPS) is reported. Compared with a slow heating rate, the electric field produced by an ultrafast heating rate enhances the liquid phase mass transfer of the metal binder phase, thus achieving rapid densification of (Ti,W)C cermets and effectively inhibiting abnormal grain growth. However, an excessive heating rate will lead to an “overflow” phenomenon, which reduces the grain growth difficulty and the bonding strength between grains. The results show that when the heating rate is 500 °C/min, the liquid phase mass transfer is moderate, the densification degree is the highest and the mechanical properties are excellent. The flexural strength, Vickers hardness and fracture toughness are 1340.90 ± 23.55 MPa, 18.42 ± 0.46 GPa and 11.96 ± 0.23 MPa∙m1/2, respectively.

Biodeterioration of Compost-Pretreated Polyvinyl Chloride Films by Microorganisms Isolated From Weathered Plastics.

Polyvinyl chloride (PVC) is a petroleum-based plastic used in various applications, polluting the environment because of its recalcitrance, large content of additives, and the presence of halogen. In our case study, a new, two-stage biodegradation technology that combined composting process used for PVC pretreatment with a subsequent PVC attack by newly-isolated fungal and bacterial strains under SSF conditions was used for biodegradation of commercial PVC films. The novelty consisted in a combined effect of the two biodegradation processes and the use for augmentation of microbial strains isolated from plastic-polluted environments. First, the ability of the newly-isolated strains to deteriorate PVC was tested in individual, liquid-medium- and SSF cultures. Higher mass-reductions of PVC films were obtained in the former cultures, probably due to a better mass transfer in liquid phase. Using the two-stage biodegradation technology the highest cumulative mass-reductions of 29.3 and 33.2% of PVC films were obtained after 110 days with Trichoderma hamatum and Bacillus amyloliquefaciens applied in the second stage in the SSF culture, respectively. However, FTIR analysis showed that the mass-reductions obtained represented removal of significant amounts of additives but the PVC polymer chain was not degraded.