Fluid Mixtures Research Articles

Modelling and Characterization of an Ice Storage for Optimized Operation

Ice storage systems (ISS) present a flexible option for the storage of thermal energy. However, due to the distinctive nature of the phase change, issues arise with ISS that are not present in conventional thermal energy storage systems. This mainly concerns the determination of the state of charge (SOC) of the ice storage during operation, as the SOC of conventional sensible thermal energy storages can be determined by a simple temperature measurement. Nevertheless, this method is not sufficient for ISS due to the constant temperature during phase changes. However, knowledge of the SOC is essential for optimum operation of the whole system. Therefore, this work deals with the modelling and experimental characterization of an ISS. The mathematical modelling is performed using a one-dimensional, discrete, dynamic model. The integration of fluid property models allows a continuous calculation of the thermodynamic properties of the fluid during the simulation. The model calculates the heat transfer coefficients, the heat flow, the transported energy and the current SOC of the ISS. Furthermore, the model has been designed to be as flexible as possible. Therefore, both icing and de-icing processes can be simulated (de-icing process shown in Figure (a)). Additionally, a variety of fluid mixtures, including water with distinct glycol proportions, can be simulated. In order to validate the results obtained in the simulation, an ice storage setup with stainless steel spiral heat exchanger has been equipped with appropriate measurement equipment. This includes temperature sensors at different locations of the ice storage tank as well as the measurement of all necessary fluid properties of the heat transfer fluid. Additionally, a capacitive sensor placed alongside the heat exchanger is employed to measure the current degree of icing in the storage (Figure (b)). Ice and water have different dielectric constants, which is utilized here to determine the ice thickness. Initial comparisons between the simulation and measurement results demonstrate a high degree of agreement. This work uses the local measurement and simulation data to make a global state of charge estimation for ISS.

In vitro evaluation of slow-release urea compounds.

The objective of this study was to evaluate the effects of different slow-release urea (SRU) compounds on ruminal fermentation, nutrient degradation, and nitrogen (N) utilization in a dual-flow continuous-culture system (experiment 1), as well as ammonia-N (NH3-N) release rate in a batch culture system (experiment 2). In experiment 1, 8 fermenters were used in a replicated 4 × 4 Latin square design with 4 treatments and 4 experimental periods. The treatments were formulated to contain the same amount of N, differing in the source of nonprotein N, such as control (CON), with noncoated urea at 0.62% DM; partial inclusion of SRU compound 1 (SRU1) at 0.51% DM; partial inclusion of SRU compound 2 (SRU2) at 0.51% DM; and partial inclusion of SRU compound 3 (SRU3) at 0.51% DM. Each period lasted 10 d. The last 3 d of each period were used for sample collection. Samples were collected for pH, lactate, VFA, NH3-N kinetics, nutrient degradability, and N metabolism. In experiment 2, a batch culture incubation was conducted as a complete randomized block design, using 3 Erlenmeyer flasks per treatment in 3 runs. Each treatment contained 1 of the 4 NPN sources used in experiment 1, (CON, SRU1, SRU2, SRU3) or without any NPN (blank, BK), and samples were collected at different time points for NH3 analysis. All flasks, except for BK, contained equal amounts of 21.56 mg N, and all flasks were inoculated with 260 mL of a 1:2 mixture of ruminal fluid and nutritive solution. Data of both experiments 1 and 2 were analyzed using the MIXED procedure of SAS. In experiment 1, there were no effects of treatment on pH or NH3-N kinetics. There were no effects of treatments on lactate kinetics; however, there was an interaction between treatment and time. For 24-h VFA pool, there were treatment effects on acetate, propionate, acetate:propionate ratio (A:P), and branched-chain (BC)VFA proportion. Compared with CON, SRU1 had lower A:P ratio and acetate proportion, with greater proportion of propionate, which could represent a favorable fermentation partner compared with CON. Treatment SRU1 had lower BCVFA proportion than the other treatments, which indicates less protein degradation. There were no treatment effects for nutrient degradability and N flow. Based on observations in experiment 1, SRU1 could have the potential of improving ruminal fermentation and N utilization. Moreover, the different SRU compounds had different fermentation patterns according to their VFA profiles. In experiment 2, there were significant effects for treatment and time, and a tendency for treatment by time interaction effect. The N release rate of SRU1 was similar to CON and faster than SRU2 and 3, and the differences in N release rates could be detected as early as at 0.75 h of incubation. Thus, SRU1 may not be as slow degrading when compared with SRU2 and 3. In conclusion, no effects were found on nutrient degradability and N utilization. However, the different SRU compounds had different N release rates, which could affect ruminal fermentation pattern in different diets.

Changes in chemical speciation and mobility of arsenic during the mixing of arsenic-bearing "snow-melting" system effluent and river water in the Ishikari Plain, Japan.

Changes in chemical speciation and mobility of arsenic during the mixing of arsenic-bearing "snow-melting" system effluent and river water in the Ishikari Plain, Japan.

A sharp volatile-rich cap to the Yellowstone magmatic system.

The stability of hazardous volcanic systems is strongly influenced by the uppermost magma storage depth and volatile exsolution1-3. Despite abundant evidence for an upper crustal magma reservoir beneath Yellowstone caldera4-7, its depth and the properties at its top have not been well constrained. New controlled-source seismic imaging illuminates a sharp reflective cap of the magma reservoir approximately 3.8 km beneath the northeastern caldera. Magma ascent to such low pressure is expected to drive volatile exsolution and potentially localized accumulation of bubbles near the top of the reservoir8,9, but this process typically remains hidden in contemporary volcanic systems. P-wave and P-to-S-wave reflections from the sharp top of the Yellowstone magma reservoir indicate that a mixture of supercritical fluid and magma fills the pore space at the cap of the approximately 3-8-km-deep low-shear-velocity layer imaged by seismic tomography6,7. The results are consistent with partial retention of bubbles exsolved from an upper crustal reservoir with ongoing magma supply from a volatile-enriched mantle source. Bubble accumulation can eventually lead to reservoir instability2,8, but the bubble volume fraction seismically estimated at the top of the reservoir today is lower than typical estimates of pre-eruptive conditions for rhyolites1,10,11, and measurements of the hydrothermal system document high fluxes of magmatic volatiles escaping to the surface12-15. We infer that the magma reservoir is in a stable state of efficient bubble ascent into the hydrothermal system on the basis of estimates that it is a crystal-rich (less than 30% porosity) reservoir for which dynamic modelling favours channelized bubble escape that prevents instability8.

A Thermodynamic Model for the Solubility of SO2 in Multi-Ion Electrolyte Solutions and Its Applications

A solubility model of SO2 in multi-ion electrolyte solutions has been developed by the activity-fugacity relation at vapor-liquid equilibria. The fugacity coefficient of SO2 in the vapor phase is calculated by the equation of state (EOS) of pure SO2, and the activity coefficient of SO2 in the liquid phase is calculated by the Pitzer activity coefficient theory. The model can reproduce the reliable solubility data of SO2 in pure water and multi-ion electrolyte solutions (Na+, K+, Cl−, SO42−) within or close to experimental uncertainties. Although the second-order and third-order interaction parameters between SO2 and Mg2+ and Ca2+ have been adopted by an approximation, the solubility model can also be extended to predict the SO2 solubility in seawater. In addition, combining with the EOS of a CO2-SO2 fluid mixture, the model can be used to predict the solubility of a CO2-SO2 mixture in aqueous electrolyte solutions. The calculated results are consistent with experimental data, which indicates that the solubility model has certain predictive ability.

Fluctuation amplitudes of a trapped particle in a near-critical binary fluid mixture

We assume that a binary fluid mixture, lying in the one-phase region near the demixing critical point, contains a Brownian particle trapped by a harmonic potential. A mixture component, preferred by the particle surface via a short-range interaction, concentrates near the surface to generate a thick adsorption layer. This layer, deformed by particle motion, increases the effective mass and restoring force, thereby reducing the equal-time correlation of the fluctuations of the particle position and that of the particle velocity. We calculate these fluctuation amplitudes using the reversible part of hydrodynamics on the basis of the free-energy density of a local functional theory, which is known to describe the critical properties well. The effects of the preferential adsorption are negligible when the stiffness of the trapping potential is sufficiently large. A typical stiffness below which the effects emerge is largely determined by the strength of preferential adsorption and shifts toward larger stiffness as the adsorption is stronger. Plots of the fluctuation amplitudes against the stiffness are approximately independent of the deviation of the temperature from the critical temperature. These properties should facilitate future experimental studies on this phenomenon.

Foam stabilization in salt solutions: The role of capillary drainage and Marangoni stresses.

Foam stabilization in salt solutions: The role of capillary drainage and Marangoni stresses.

Manipulation of meniscus rise for in situ multiphase nuclear magnetic resonance spectroscopy

Our earlier work demonstrated that nuclear magnetic resonance (NMR) spectroscopy is a viable technique for in situ analysis of vapor–liquid equilibria (VLE) of fluid mixtures and that inserting a capillary into the NMR sample tube allows the simultaneous collection of separate liquid- and vapor-phase spectra for composition determination. This is the result of a thin film of liquid wicking up due to capillary forces into the vapor space, which was not possible with the undisturbed meniscus in the absence of a capillary. The present study investigates the meniscus rise (i.e., capillary action) effect in detail. We use three-dimensional (3D) computational fluid dynamics to investigate the flow regime of the liquid wicking in the NMR tube considering the flow as inviscid, low-viscosity laminar, or viscous-laminar. Thus, we can predict the liquid-volume fraction as a function of the capillary diameter and fluid properties. These results are compared to, and validated against, x-ray computed tomography experiments, which provided detailed (8 μ m resolution) 3D imaging of the meniscus of decane in an NMR tube. Phase determination of liquid and vapor cyclopentane in an NMR spectrometer provided additional validation, although integrated over a 10-mm high detection volume. Both meniscus height and thickness are significant variables to modify; thus, in situ VLE studies with NMR can be improved. We demonstrate that the prediction of the effect of capillary geometry on NMR signals for liquid and vapor phases of a pure compound can be used for rapid optimization in NMR VLE measurements.

Open Boundaries, Anomalous Diffusion and the Darcy-Bénard Instability

The classical problem of the Darcy-Bénard instability in a horizontal porous layer saturated by a binary fluid mixture and subject to a non-uniform solutal concentration field is revisited. In particular, a generalised anomalous diffusion model departing from the classical Fickian diffusion and accounting for subdiffusion or superdiffusion phenomena is employed. At the porous layer boundaries, a uniform vertical concentration gradient is imposed, so that an unstable density stratification arises. The boundaries are modelled as open, meaning that uniform pressure conditions are prescribed. A linear stability analysis of the basic rest state is carried out, showing how the departure from the classical Fickian diffusion affects dramatically the conditions for the onset of the instability.

Far-from-equilibrium attractors in kinetic theory for a mixture of quark and gluon fluids

Far-from-equilibrium attractors in kinetic theory for a mixture of quark and gluon fluids

Efficient Phase Equilibrium Calculations of Shale Reservoir Fluids—Part I: New Fast and Robust Trust Region–Based Algorithm with Volume Variables at Isobaric-Isothermal Conditions

Summary Volume-based phase equilibrium calculations (PECs) are gaining increasing attention because the traditional Gibbs free-energy-based PECs encounter various convergence issues when capillary pressure is introduced. However, the conventional successive substitution iteration (SSI) is inapplicable without modification to volume-based PECs, thus necessitating a robust and efficient algorithm. In this study, we developed a unified trust region (TR) Newton-based algorithmic framework for volume-based PECs at isothermal-isobaric conditions, encompassing phase stability analysis (PSA) and flash calculations (FCs), with both formulated as minimization problems. Unlike traditional line search methods, which separately determine the step direction and length, the TR method integrates both processes to ensure faster and more reliable convergence. To further enhance robustness, we incorporate problem-specific constraint checks for PSA and FCs and solve TR subproblems using the near-exact approach. A key feature of our approach is the analytical generation of Hessian matrices using the Automatically Differentiable Expression Templates Library (ADETL), enabling high computational precision. Extensive testing on four fluid mixtures demonstrates that the TR-based algorithm is both rapid and robust, effectively addressing challenges such as the stability testing limit locus (STLL), spinodal curves in PSA, and critical regions in FCs. This work represents the first application of TR algorithms in volume-based PECs, providing a solid foundation for further developments, including the integration of capillary pressure. The proposed framework offers significant potential for compositional simulations of unconventional oil and gas reservoirs, ensuring accuracy and efficiency in complex PECs.

Density measurements of homogeneous phase fluid mixtures comprising CO2/propanol and CO2/butanol binary systems and correlation with PC-SAFT equation of state

Density measurements of homogeneous phase fluid mixtures comprising CO2/propanol and CO2/butanol binary systems and correlation with PC-SAFT equation of state

Modeling and numerical simulation of concentrated solar energy storage using fluidized bed systems

AbstractOne of the challenges to using concentrated solar energy (CSE) is the development of innovative fluids or mixtures of fluid and particle systems to efficiently adsorb concentrated solar radiation and transfer heat. In this article, the large‐eddy simulation (LES) model and a computational fluid dynamics (CFD) approach were used to simulate CSE absorption by a fluidized bed of silicon carbide (SiC). Drag‐forced modification was developed based on the Clark sub‐grid model for fluidized beds. The result of our two‐dimensional simulation agreed well with Tregambi et al. experimental data. Our simulation showed that the fluidized bed reduced the surface temperature by convective energy transfer, which is only on the surface for the incipiently fluidized bed and in the entire fluidized bed for the bubbling fluidized bed due to the mixing created by bubbles. The lower temperature on the surface significantly decreased the radiative energy loss from the surface to the environment.

Theory and Modeling of Transport for Simple Fluids in Nanoporous Materials: From Microscopic to Coarse-Grained Descriptions.

We present the state-of-the-art of theoretical modeling, molecular simulation, and coarse-graining strategies for the transport of gases and liquids in nanoporous materials (pore size 1-100 nm). Special emphasis is placed on the transport of small molecules in zeolites, active carbons, metal-organic frameworks, but also in nanoporous materials with larger pores such as ordered and disordered mesoporous oxides. We present different atomistic and mesoscopic methods as well as available theoretical formalisms to describe such a complex problem. Attention is given to the investigation of different molecular transport coefficients─including the self, collective and transport diffusivities─but also to the determination of free energy barriers and their role in overall adsorption/separation process rates. We further introduce other available approaches such as hierarchical simulations and upscaling strategies. This review focuses on simple fluids in prototypical nanoporous materials. While the phenomena covered here capture the main physical mechanisms in such systems, complex molecules will exhibit additional specific features. For the sake of clarity and brevity, we also omit multicomponent systems (e.g., fluid mixtures, electrolytes, etc.) and electrokinetic effects arising when charged systems are considered (ionic species, charged surfaces, etc.), both of which add to the complexity.

Gaseous PVTx Properties of the CO2-N2O Binary Mixture: Experiment and Simulation.

Anthropogenic greenhouse gases are mainly CO2, CH4, N2O, and fluorinated gases. However, due to the toxicity of the CO2-N2O mixture, there are few experimental pressure-volume-temperature-composition (PVTx) data available in the literature, which do not meet the temperature-pressure conditions for the applications of carbon capture and storage (CCS). In this work, the gaseous PVTx data of the CO2-N2O mixture with molar ratios of 0.6:0.4 and 0.8:0.2 were measured by using a constant-volume vapor phase density apparatus, over a temperature-pressure range of 298.15-473.15 K and 1.0-100.0 bar. The relative standard uncertainty of density ranged from 0.15 to 0.35%. Based on experimental data, a Helmholtz free energy equation of state (EOS) for the CO2-N2O mixture was developed, which can accurately reproduce the PVTx properties of the CO2-N2O fluid mixture. The EOS reveals that as the N2O content increases, the density of the CO2-N2O fluid mixture initially decreases and then increases. The overall trend shows that the density decreases with increasing temperature and increases with increasing pressure. The EOS can be used to quantitatively estimate the effect of impurity N2O on the CO2 storage capacity in the CCS process.

Non-ideal mixing of lipids: A molecular dynamics perspective.

Lipid membranes have complex compositions, and modeling the thermodynamic properties of multi-component lipid systems remains a remote goal. In this work, we attempt to describe the thermodynamics of binary lipid mixtures by mapping coarse-grained molecular dynamics systems to two-dimensional simple fluid mixtures. By computing and analyzing the density fluctuations of this model lipid bilayer, we determine the numerical value of the quadratic coupling term appearing in a model of regular solutions for the dipalmitoylphosphatidylcholine-dilinoleoylphosphatidylcholine pair of lipids at three different compositions. Our methodology is general and discussed in detail.

Periodic Phase‐Separation During Meniscus‐Guided Deposition

AbstractThe meniscus‐guided coating (MGC) of a binary fluid mixture containing a solute and a volatile solvent that undergoes spinodal decomposition is investigated numerically. Motivation is the evaporation‐driven deposition of material during the fabrication of organic thin film electronics. A transition in the phase‐separation morphology from an array of droplet‐shaped domains deposited periodically parallel to the slot opening to isotropically dispersed solute‐rich droplets with increasing coating velocity is found. This transition originates from the competition between the injection of the solution into the film and diffusive transport that cannot keep up with replenishing the depletion of solute near the domains. The critical velocity of the transition is determined by the ratio of two length scales: i) the spinodal length, which implicitly depends on the evaporation rate and the properties of the solution, and ii) a depletion length proportional to the ratio of the diffusivity of the solute and the coating velocity. For coating below the critical velocity, the domain size and deposition wavelength are proportional to a solute depletion length. This competition in the mass transport is inherent in any kind of unidirectional deposition of demixing solutions and the findings should therefore apply to many coating techniques and forced demixing processes.

Conservative, bounded, and nonlinear discretization of the Cahn-Hilliard-Navier-Stokes equations

Conservative, bounded, and nonlinear discretization of the Cahn-Hilliard-Navier-Stokes equations

Analisis Perbandingan Tegangan Pada Baterai Berbahan Baku Limbah Barubara dengan Kulit Pisang sebagai Energi Alternatif

Electrical energy is one of the foundations that supports modern progress in various aspects of social and economic life. The source of electrical energy currently used is still considered insufficient to meet human needs, so alternative energy is needed. Alternative energy is an environmentally friendly energy and can be renewed by utilizing waste. One of the promising alternative raw materials is the use of fly ash and bottom ash, which are waste from coal combustion in steam power plants. In the process of utilizing fly ash and bottom ash as raw materials for batteries, special processing and technology are required in order to produce effective and efficient products. On the other hand, the latest innovations show that banana peels, which are generally considered organic waste, also have the potential to be used as a raw material in making batteries. A battery consists of one or more electrochemical cells that are electrically connected and have terminals or contacts to provide electrical energy. As a research method, this emphasizes voltage, current and endurance tests. In this test, the voltage, current and endurance produced by the battery assembly are tested and compared after being given variations in the composition of raw materials. From the experimental results above, it is concluded that fly ash and bottom ash batteries with a mixture of electrolytes get the highest results with a voltage of 1.13 V and a current of 0.111 A then tested on a wall clock that lasted for 5 days. The battery with the highest durability is obtained by a battery containing fly ash and bottom ash with a mixture of electrolyte fluids, but a battery containing banana peels with a mixture of sea water can turn on the clock for 9 hours. Keywords— Fly ash, Bottom Ash, Battery, Banana Peel, Electrolyte

On the existence of prewetting in supracritical fluid mixtures.

We demonstrate the existence of a first-order prewetting transition of a supracritical model polymer solution adjacent to an attractive surface. The model fluid we use mimics (qualitatively) an aqueous polyethylene oxide solution and, like the actual solution, displays a closed loop 2-phase region with an upper and lower critical solution temperature. The model fluid is shown to undergo a prewetting transition at an adjacent attractive surface. For sufficiently strong surface affinities, the prewetting transition may occur even at temperatures below the lower critical solution temperature (supracriticality). This phenomenon follows from non-local thermodynamics when the length-scale of the relevant fluid structures of surface films are commensurate or smaller than the range of intermolecular interactions.