Dispersive Mixing Research Articles

Investigation of the thermal structure in the atmospheric boundary layer during evening transition and the impact of aerosols on radiative cooling

AbstractThe evening transition is crucial in various phenomena, including boundary‐layer stability, temperature inversion, radiation fog, vertical mixing, and pollution dispersion. We have explored this transition using data from 80 days of observations across two fog seasons at the Kempegowda International Airport, Bengaluru (KIAB). Through field experiments and simulations integrating aerosol interaction in a radiation–conduction model, we elucidate the impact of aerosols on longwave cooling of the atmospheric boundary layer (ABL). Field observations indicate that, under calm and clear‐sky conditions, the evening transition typically results in a distinct vertical thermal structure called the lifted temperature minimum (LTM). We observe that the prevailing profile near the surface, post‐sunset is the LTM profile. Additionally, the occurrence of LTM is observed to increase with decreases in downward and upward longwave flux, soil sensible heat flux, wind speed, and turbulent kinetic energy measured at 2 m above ground level (AGL). In such scenarios, the intensity of LTM profiles is governed primarily by the aerosol‐induced longwave heating rate (LHR) within the surface layer. Furthermore, the presence of dense clouds leads to increased downward flux, causing the disappearance of LTM, whereas shallow fog can enhance LTM intensity, as observed in both field observations and simulations. Usually, prevailing radiation models underestimate aerosol‐induced LHR by an order of magnitude compared with actual field observations. We attribute this difference to aerosol‐induced radiation divergence. We show that the impact of aerosol‐induced LHR extends hundreds of meters into the inversion layer, affecting temperature profiles and potentially influencing processes such as fog formation. As the fog layer develops, LHR strengthens at its upper boundary. However, we highlight the difficulty in detecting this cooling using remote instruments such as microwave radiometers.

EFFECT OF N-PHENYLAMINOPROPYL POLYHEADRAL OLIGOMERIC SILSESQUIOXANE DISPERSION METHOD ON STRUCTURE-PROPERTY RELATIONSHIPS FOR THERMOSTABLE POLYCYANURATE-BASED NANOCOMPOSITES

In this work, the effect of the method of dispersion of a reactive N-phenylaminopropyl polyhedral oligomeric silsesquioxane (NPAP-POSS, 0.025 wt.%) with eight secondary amino groups, in dicyanate ester of bisphenol E (DCBE) on the chemical processes occurring in reactive DCBE/NPAP-POSS blends during dispersion, as well as on the chemical structure, viscoelastic, thermophysical, and thermal properties of heat-resistant organic-inorganic PCN/NPAP-POSS nanocomposites was investigated. The synthesis of the nanocomposite samples was carried out in two stages. In the first stage, to improve the efficiency of nanofiller dispersion, high-speed mechanical or ultrasonic mixing of NPAP-POSS with DCBE was used at different temperatures (T = 65 °C, T = 165 °C), which ensured the chemical interaction of the components. In the second stage, PCN/NPAP-POSS nanocomposites were synthesized by in situ high-temperature reactive molding by dynamic heating the samples in the temperature range of T = 20–300 °C. Using dynamic mechanical thermal analysis (DMTA) for PCN/NPAP-POSS nanocomposites synthesized by high-speed mechanical or ultrasonic mixing at a temperature of T = 65 °C, an unusually significant increase (by 26.5–28.5 °C compared to PCN) in the glass transition temperature (Tg) of the samples even at ultra-low NPAP-POSS content. This phenomenon demonstrates the so-called nanoscale effect. It was also found that the method of nanofiller dispersion affects the increase (compared to unfilled PCN) of the storage modulus (E’) and other viscoelastic properties, as well as the apparent network density (v) and the apparent average molecular weight (Mc) between crosslinks in the hybrid network matrix of the nanocomposites. Differential scanning calorimetry (DSC) also showed that the dispersion method changes the thermophysical properties of the synthesized PCN/NPAP-POSS nanocomposites. This effect is associated with the formation of additional organic-inorganic crosslinks due to the chemical embedding of NPAP-POSS nanoparticles and the formation of the hybrid PCN/NPAP-POSS network. Fourier transform infrared (FTIR), 1H NMR, and 13C NMR spectroscopy confirmed that during nanofiller dispersion in DCBE/NPAP-POSS reactive blends, a chemical interaction occurs between the –O–C≡N groups of DCBE and the secondary –NH groups of NPAP-POSS. This interaction is confirmed by the appearance of corresponding absorption bands and signals (chemical shifts) in the spectra indicating the formation of intermediate isourea fragments and triazine rings of polycyanurates. It was concluded that ultrasonic dispersion of the nanofiller is the most effective under these synthesis conditions for PCN/NPAP-POSS nanocomposites as it ensures the highest degree of cyanate group conversion in DCBE at the final stages of synthesis (confirmed by DMTA data), thereby extending the range of working temperatures within which the samples retain their mechanical and physical properties. Using thermogravimetric analysis (TGA), it was found that all nanocomposites exhibit high resistance to thermo-oxidative degradation (Td > 440 °C), which is largely unaffected by the method of nanofiller dispersion and is determined by the chemical structure of the densely cross-linked PCN/NPAP-POSS hybrid network.

Component Distribution, Shear-Flow Behavior, and Sol-Gel Transition in Mixed Dispersions of Casein Micelles and Serum Proteins.

The shear flow and solid-liquid transition of mixed milk protein dispersions with varying concentrations of casein micelles (CMs) and serum proteins (SPs) are integral to key dairy processing operations, including microfiltration, ultrafiltration, diafiltration, and concentration-evaporation. However, the rheological behavior of these dispersions has not been sufficiently studied. In the present work, dispersions of CMs and SPs with total protein weight fractions (ωPR) of 0.021-0.28 and SP to total protein weight ratios (RSP) of 0.066-0.214 and 1 were prepared by dispersing the respective protein isolates in the permeate from skim milk ultrafiltration and then further concentrated via osmotic compression. The partition of SPs between the CMs and the dispersion medium was assessed by measuring the dry matter content and viscosity of the dispersion medium after separating it from the CMs via ultracentrifugation. The rheological properties were studied at 20 °C via shear rheometry, and the sol-gel transition was characterized via oscillatory measurements. No absorption of SPs by CMs was observed in dispersions with ωPR = 0.083-0.126, regardless of the RSP. For dispersions of SPs with ωPR ≤ 0.21, as well as the dispersion medium of mixed dispersions with ωPR = 0.083-0.126, the high shear- rate-limiting viscosity was described using Lee's equation with an SP voluminosity (vSP) of 2.09 mL·g-1. For the mixed dispersions with a CM volume fraction of φCM ≤ 0.37, the relative high shear-rate-limiting viscosity was described using Lee's equation with a CM voluminosity (vCM) of 4.15 mL·g-1 and a vSP of 2.09 mL·g-1, regardless of the RSP. For the mixed dispersions with φCM > 0.55, the relative viscosity increased significantly with an increasing RSP (this was explained by an increase in repulsion between CMs). However, the sol-gel transition was independent of the RSP and was observed at φCM ≈ 0.65.

Analysis of the Dispersive and Distributive Mixing Effect of Screw Elements on the Co-Rotating Twin-Screw Extruder with Particle Tracking.

Compounding is an important step in processing base polymers and is used to incorporate various additives into a polymer. For this purpose, different screw elements are used for dispersive and distributive mixing on a co-rotating twin-screw extruder. Optimising the screw configuration requires precise knowledge of the screw elements' mixing properties, which have not been thoroughly investigated. This study analyses the mixing behaviour of individual screw elements regarding dispersive and distributive mixing using 3D CFD flow simulations with subsequent particle tracking. For distributive mixing, the particle distribution behind the screw elements in the XY plane is analysed and the mixing index MQ, which relates the standard deviation and the mean value of the triangular areas between the particles, is calculated. For dispersive mixing, the maximum shear stress on the particle path and the integral of the shear stress over the residence time of each individual particle are determined. The results show that screw element geometry and rotation speed have a significant influence on dispersive and distributive mixing. In addition, better dispersive mixing is achievable with highly viscous materials. These findings enable the optimisation of the mixing zone of a co-rotating twin-screw extruder for the efficient mixing of mineral fillers.

Tuning thermal stability of fluorine-free foam by nano-MDH inorganic flame retardant

Foams enhanced by nanoparticles (NPs) have become an important way to develop new type of fluorine-free firefighting foams. This study focuses on thermal stability of foams generated by the mixed dispersion of CoatOsil-77 silicone and BS-12 hydrocarbon surfactants as foaming agent and nano-magnesium hydroxide (nano-MDH) as foam stabilizer. The interaction between nano-MDHs and surfactants were studied. Thermal stability of nano-MDH enhanced foam was explored by investigating drainage and volume attenuation of foam and heat transfer in vertical foam blanket. Stabilization mechanism of nano-MDH enhanced foam under heat was clarified. Results show that nano-MDHs have a weak interaction with the BS-12 molecules and almost has no interaction with the CoatOsil-77 molecules. Initial foam height of mixed dispersion increases at the presence of nano-MDHs, but further increase in the concentration of nano-MDH decreases its foaming ability. At room temperature, foam drainage and coarsening are accelerated by low concentration nano-MDH (1 wt%) and delayed by high concentration nano-MDH (>1 wt%). Meanwhile, foam was strengthened by rising nano-MDH content after exceeding 1 wt%. Drainage and volume attenuation of foam and heat transfer in vertical foam blanket were significantly delayed and the corresponding thermal stability was strengthened by nano-MDHs. This study can offer a possibility for tuning thermal stability of fluorine-free foams based on nano-MDHs.

Effect of Mixing Methods and Black Conductive Fillers on Properties of Natural Rubber Composites

Carbon black, graphite, carbon nanofibers, carbon nanotubes, and metal fillers increase composite conductivity in natural rubber, which is electrically insulating. Depending on dispersion, conductive filler lowers insulating material resistivity. These materials are frequently used for electromagnetic/radio frequency interference (EMI/RFI) shielding, conductive flexible seals gaskets, and conductive mats used to prevent electrostatic damage to electronic devices. These elastomers could be used to make flexible solar cells or mechanical-to-electricity devices. Temperature, mixing time, shear rate, and cross-linking during vulcanization affect rubber electrical conductivity of composite. To study shear rate effects, vulcanizate of Natural Rubber-based composites filled with carbon black, millable carbon fiber powder, and synthetic graphite powder was prepared by open mixing (two roll mill) and close mixing (internal mixer). We compared how shear rate affects cure, stress-strain, and volume resistivity of conductive filler-based Natural Rubber composites. Increment in clearance of two roll mill during addition of rubber additives along with rubber of reduced the shearing force resulted in less dispersive and distributive mixing and stagnant points due to band formation on roll surface compared to intermix where compound movement had no stagnation point and long wings pushed material axially and two nogs pushed material in other chamber. Compared to two roll mill samples, the compound reached every point of the mixing chamber for best homogeneity, reducing cure time and improving stress-strain and volume resistivity.

Controls insensitizing the norm of solution of a Schrödinger type system with mixed dispersion

The main goal of this manuscript is to prove the existence of insensitizing controls for the fourth-order dispersive nonlinear Schrödinger equation with cubic nonlinearity. To obtain the main result we prove a null controllability property for a coupled fourth-order Schrödinger cascade type system with zero-order coupling which is equivalent to the insensitizing control problem. Precisely, employing a new Carleman estimates, we first obtain a null controllability result for the linearized system around zero, and then the null controllability for the nonlinear case is extended using an inverse mapping theorem.

Significantly Enhanced Oxidation Resistance and Electrochemical Performance of Hydrothermal Ti3C2Tx MXene and Tannic Acid Composite for High-Performance Flexible Supercapacitors.

The electrochemical performances of Ti3C2Tx MXene are severely restricted by the easy oxidation and restacking. Herein, tannic acid (TA) is introduced into Ti3C2Tx dispersion, and the mixed dispersion is further subjected to a simple hydrothermal treatment to prepare the hydrothermal Ti3C2Tx and TA composite (h-Ti3C2Tx@h-TA). Due to the decomposition of TA into gallic acid (GA), hydrothermal TA (h-TA) is a mixture of TA and GA. The strong interaction between h-TA and MXene mainly involves chemical interaction between the hydroxyl groups in h-TA and the surface/edge Ti atoms, along with numerous hydrogen bonds. The h-TA intercalation weakens MXene restacking and increases interlayer spacing, thereby improving ion transport pathways and accessibility. The chemical interaction between the hydroxyl groups of GA and the Ti atoms significantly enhances oxidation resistance and pseudocapacitive active sites. Therefore, the h-Ti3C2Tx@h-TA film electrode shows significantly enhanced capacitance (848 F·g-1 at 1 A g-1) and cycling stability (100% retention after 20 000 cycles). Moreover, flexible sandwiched supercapacitors with symmetrical h-Ti3C2Tx@h-TA electrodes exhibit a high energy density of 30.1 Wh kg-1 at a high power density of 300 W kg-1, outperforming those of Ti3C2Tx-based film electrodes and sandwiched supercapacitors reported so far. The extrusion-printed microsupercapacitors with h-Ti3C2Tx@h-TA electrodes demonstrate high areal capacitance (135 mF cm-2 at 5 mV s-1) along with energy storage performance (6.74 μWh cm-2 at 506 μW cm-2) and cycling stability (98.8% retention after 41 460 cycles), all while maintaining excellent flexibility. These impressive results indicate the great application potential of the hydrothermal Ti3C2Tx MXene and tannic acid composite in flexible energy storage devices.

Magneto-Stokes flow in a shallow free-surface annulus

In this study, we analyse ‘magneto-Stokes’ flow, a fundamental magnetohydrodynamic (MHD) flow that shares the cylindrical-annular geometry of the Taylor–Couette cell but uses applied electromagnetic forces to circulate a free-surface layer of electrolyte at low Reynolds numbers. The first complete, analytical solution for time-dependent magneto-Stokes flow is presented and validated with coupled laboratory and numerical experiments. Three regimes are distinguished (shallow-layer, transitional and deep-layer flow regimes), and their influence on the efficiency of microscale mixing is clarified. The solution in the shallow-layer limit belongs to a newly identified class of MHD potential flows, and thus induces mixing without the aid of axial vorticity. We show that these shallow-layer magneto-Stokes flows can still augment mixing in distinct Taylor dispersion and advection-dominated mixing regimes. The existence of enhanced mixing across all three distinguished flow regimes is predicted by asymptotic scaling laws and supported by three-dimensional numerical simulations. Mixing enhancement is initiated with the least electromagnetic forcing in channels with order-unity depth-to-gap-width ratios. If the strength of the electromagnetic forcing is not a constraint, then shallow-layer flows can still yield the shortest mixing times in the advection-dominated limit. Our robust description of momentum evolution and mixing of passive tracers makes the annular magneto-Stokes system fit for use as an MHD reference flow.

Gas–liquid mixing performance of a non‐Newtonian fluid in a multiple‐impeller agitated tank

AbstractBACKGROUNDThis target is to decide power input and gas hold‐up for gas–liquid mixing aqueous CMC solutions. The analysis considers the impact by varying the impeller speed and gas flow rates in a stirred tank bioreactor of three kinds of multiple impellers. The effects of the impeller type, rheology, and operating conditions were investigated on power drawn, relative power demand (RPD), gas holdup, and volumetric mass transfer coefficient.RESULTCompared to the Rushton turbine (6RT) and 4‐pitch blade (4PBT) impeller, the propeller (3PP) impeller presented a minimal event of the gassing on the RPD. 4PBT impeller has shown a higher gas hold‐up compared to the Rushton turbine and propeller impellers. The aerated agitated tank was established a dimensionless correlation for the RPD as a function of flow number and web number. Besides, the gas–liquid agitated system was also introduced a dimensionless correlation to compute the overall gas hold‐up as a function of specific power consumption. For the maximum dispersion mixing intensity, the impeller structure with low RPD looks to be more adequate. Further, maximizing gas holdup in the structures with high RPD is advantageous. The effects of impeller speed, gas superficial velocity, and rheology on the volumetric mass transfer coefficient were examined.CONCLUSIONThe volumetric mass transfer coefficient increased with an increase in impeller speed, gas superficial velocity, and power consumption per unit volume and decreased as rheology increased. The averaged kLa for each multiple‐impeller was correlated well with the specific gassed power consumption and gas superficial velocity. © 2024 Society of Chemical Industry (SCI).

Analyzing Homogeneity of Highly Viscous Polymer Suspensions in Change Can Mixers.

The mixing of highly viscous non-Newtonian suspensions is a critical process in various industrial applications. This computational fluid dynamics (CFD) study presents an in-depth analysis of non-isothermal mixing performance in change can mixers. The aim of the study was to identify parameters that significantly influence both distributive and dispersive mixing in these mixers, which are essential for optimizing industrial mixing processes. The study employed a numerical design of experiments (DOE) approach to identify the parameters that most significantly influence both distributive and dispersive mixing, as measured by the Kramer mixing index (MKramer) and the Ica Manas-Zloczower mixing index λMZ¯. The investigated parameters included mixing time, number of arms, arm size ratio, revolutions per minute (RPM), z-axis rotation, z-axis movement, and initial and mixing temperatures. The methodology involved employing the bootstrap forest algorithm for predicting the mixing indices, achieving an R2 of 0.949 for MKramer and an R2 of 0.836 for λMZ¯. The results indicate that the z-axis rotation has the greatest impact on both distributive and dispersive mixing. An increased number of arms negatively impacted λMZ, but had a small positive effect on MKramer. Surprisingly, in this study, neither the initial temperature of the material nor the mixing temperature significantly impacted the mixing performance. These findings highlight the relative importance of operational parameters over traditional temperature factors and provide a new perspective on mixing science.

Computational study on cilia transport of Prandtl nanofluid (blood-Fe3O4) enhancing convective heat transfer along microorganisms under electroosmotic effects in wavy capillaries

Purpose This study aims to focuse on the flow behavior of a specific nanofluid composed of blood-based iron oxide nanoparticles, combined with motile gyrotactic microorganisms, in a ciliated channel with electroosmosis. Design/methodology/approach This study applies a powerful mathematical model to examine the combined impacts of bio convection and electrokinetic forces on nanofluid flow. The presence of cilia, which are described as wave-like motions on the channel walls, promotes fluid propulsion, which improves mixing and mass transport. The velocity and dispersion of nanoparticles and microbes are modified by the inclusion of electroosmosis, which is stimulated by an applied electric field. This adds a significant level of complexity. Findings To ascertain their impact on flow characteristics, important factors such as bio convection Rayleigh number, Grashoff number, Peclet number and Lewis number are varied. The results demonstrate that while the gyrotactic activity of microorganisms contributes to the stability and homogeneity of the nanofluid distribution, electroosmotic forces significantly enhance fluid mixing and nanoparticle dispersion. This thorough study clarifies how to take advantage of electroosmosis and bio convection in ciliated micro channels to optimize nanofluid-based biomedical applications, such as targeted drug administration and improved diagnostic processes. Originality/value First paper discussed “Numerical Computation of Cilia Transport of Prandtl Nanofluid (Blood-Fe3O4) Enhancing Convective Heat Transfer along Micro Organisms under Electroosmotic effects in Wavy Capillaries”.

Normalized solutions for Chern–Simons–Schrödinger system with mixed dispersion and critical exponential growth

This paper focuses on the existence of normalized solutions for the Chern–Simons–Schrödinger system with mixed dispersion and critical exponential growth. These solutions correspond to critical points of the underlying energy functional under the ‐norm constraint, namely, . Under certain mild assumptions, we establish the existence of nontrivial solutions by developing new mathematical strategies and analytical techniques for the given system. These results extend and improve the results in the existing literature.

Investigation of the Aggregation of Aβ Peptide (1-40) in the Presence of κ-Carrageenan-Stabilised Liposomes Loaded with Homotaurine.

The kinetics of amyloid aggregation was studied indirectly by monitoring the changes in the polydispersity of mixed dispersion of amyloid β peptide (1-40) and composite liposomes. The liposomes were prepared from the 1,2-dioleoyl-sn-glicero-3-phoshocholine (DOPC) phospholipid and stabilised by the electrostatic adsorption of κ-carrageenan. The produced homotaurine-loaded and unloaded liposomes had a highly negative electrokinetic potential and remarkable stability in phosphate buffer (pH 4 and 7.4). For the first time, the appearance and evolution of the aggregation of Aβ were presented through the variation in the standard percentile readings (D10, D50, and D90) obtained from the particle size distribution analysis. The kinetic experiments indicated the appearance of the first aggregates almost 30 min after mixing the liposomes and peptide solution. It was observed that by adding unloaded liposomes, the size of 90% of the particles in the dispersion (D90) increased. In contrast, the addition of homotaurine-loaded liposomes had almost minimal impact on the size of the fractions of larger particles during the kinetic experiments. Despite the specific bioactivity of homotaurine in the presence of natural cell membranes, this study reported an additional inhibitory effect of the compound on the amyloid peptide aggregation due to the charge effects and 'molecular crowding'.

A bilateral semi-resolved CFD-DEM approach for cost-effective modelling in a rotary drum

It is of significance to numerically describe particle-flow interphase flow details at a feasible computational cost. Inspired by the semi-resolved Computational Fluid Dynamics-Discrete Element Method (CFD-DEM), an improved bilateral semi-resolved CFD-DEM approach (BSM) approach is developed in this work. Compared with the conventional divided particle volume method (DPVM) and recent semi-resolved CFD-DEM (SM) approach, the BSM approach allows a higher-resolution mesh and achieves higher accuracy as well as applicability when simulating the transient flow with sharp gradients of solid volume fraction and velocity etc. Then the BSM approach is applied to a rotary drum to demonstrate the effectiveness by investigating the internal hydrodynamics details. The typical flow behaviours are detailed; then the effects of the restitution and friction on the internal flow are analysed with details to demonstrate its effectiveness in terms of repose angle, active–passive zone, solid residence time, particle mixing and axial dispersion. The results show a positive correlation of the active depth, mixing degree, and particle dispersion with the friction, while restitution increasing depicts no significant effects on this particulate flow. This work provides an improved numerical tool for understanding the multiphase transient flows involving sharp gradients.

Taylor dispersion and phase mixing in the non‐cutoff Boltzmann equation on the whole space

AbstractIn this paper we describe the long‐time behavior of the non‐cutoff Boltzmann equation with soft potentials near a global Maxwellian background on the whole space in the weakly collisional limit (that is, infinite Knudsen number ). Specifically, we prove that for initial data sufficiently small (independent of the Knudsen number), the solution displays several dynamics caused by the phase mixing/dispersive effects of the transport operator and its interplay with the singular collision operator. For ‐wavenumbers with , one sees an enhanced dissipation effect wherein the characteristic decay time‐scale is accelerated to , where is the singularity of the kernel ( being the Landau collision operator, which is also included in our analysis); for , one sees Taylor dispersion, wherein the decay time‐scale is accelerated to . Additionally, we prove almost uniform phase mixing estimates. For macroscopic quantities such as the density , these bounds imply almost uniform‐in‐ decay of in due to phase mixing and dispersive decay.

Mixing performance in an asymmetrical non-twin kneading element channel

Abstract The kneading elements play a crucial role in the distributive and dispersive mixing in the conventional co-rotating twin screw extruders. A novel kind of asymmetrical dual-speed co-rotating non-twin kneading elements (NTKE) with a zero staggered angle was designed to introduce symmetry break to improve mixing. Finite element method was applied to solve the time-dependent flow field where mesh superposition technique was used to impose the boundary conditions of moving parts and further to avoid the remeshing at every time steps. The flow and mixing of several fluids obeying the Carreau constitutive model with the different power law exponents were investigated numerically and compared with the conventional co-rotating twin kneading elements (TKE). Distributive mixing was evaluated through evolution of tracer droplets and decaying of variance index with time. Moreover, the dispersive mixing was examined in terms of the statistical distributions of mixing index. An integral function with regard to the mixing index was proposed to evaluate the proportion of tracer particles subjected to the elongation.

P‐260: Late‐News Poster: Doping Ratio Control of Organic Composite Layer in OELDs by Spectroscopic Ellipsometry

The OLEDs industry needs a reliable nondestructive process control method for measuring the correct thickness of layers and estimation of doping or mixing ratio. Using spectroscopic ellipsometry, we applied for thickness and doping ratio monitoring for emission layer (EML) and mixed electron transport layer (mETL) grown on glass by evaporator. Optical properties of EML host and dopant, mETL host and mixing material have been investigated. We present the effect of doping on optical constants dispersions of EML and mETL layers in the photon energy range 1.2 to 5.0 eV. We adopted the Effective Medium Theory (EMT) to monitoring mixing ratio and dispersion equation to monitoring doping ratio. In result developed monitoring tool can measure imperceptible difference doping ratio.

Modelling and numerical analysis on residence time distribution characteristics in continuous high-pressure hydrothermal reactor

Residence time distribution (RTD) is significant for reflecting fluid mixing and materials dispersion inside continuous high-pressure hydrothermal reactor. In this work, a model is proposed to precisely fit RTD data in continuous hydrothermal reactor, and the model parameters can be used to analyze the characteristics of RTD. A series of RTD data under different working conditions are obtained by numerical simulation and analyzed by the proposed model to investigate the effects of natural convection, momentum ratio and forced flow on RTD. It is found that appropriate natural convection and momentum ratio are beneficial to fluid mixing and materials dispersion. On the other hand, excessive natural convection and too high or too low branch inflow may lead to the extension of average residence time and materials delay or stagnation. Forced flow is negatively correlated with average residence time but has little influence on materials dispersion and delay.

Synergies of storing hydrogen at the crest of CO2${\rm CO}_{2}$ or other gas storage

AbstractThere are mutual benefits in storing in sedimentary reservoirs jointly with another gas serving as a cushion gas, such as the of a carbon capture and storage (CCS) operation or the natural gas of seasonal storage or left in a depleted hydrocarbon reservoir. When occupies the crest of the reservoir, the presence of either gas is beneficial to the other. reinforces the sealing efficiency of the caprock due to its very favorable interfacial properties with respect to brine and rock‐forming minerals. storage safety and capacity are also increased with cushion gases such as , which alleviate the buoyancy pressure at the top of the gas column. The potential drawback of this storage scheme is gas/gas mixing, which can, however, be strongly reduced if, by an appropriate choice of well completion and placement, is positioned in the upper zones of the reservoir, and its injection rate is kept below a critical value corresponding to the incipient fingering instability of the gas mixing zone. This value, which depends on reservoir permeability, the dip angle of the mixing front, and how density varies with viscosity in the mixing front, turns out to be well above practical injection rates. Therefore, dispersive mixing is the only cause of front spreading, which is acceptable for not‐too‐heterogeneous reservoirs. The mutual benefits identified in this study are the strongest when the cushion is made up of dense , which suggests that the crest of offshore storage reservoirs is a good candidate for storage. © 2024 The Authors. Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.