Solid Interfacial Area Research Articles

A novel approach for wettability estimation in geological systems by fluid–solid interfacial area measurement using tracers

Wettability plays a vital role in many applications of flow in porous media and affects Darcy scale flow parameters by influencing the fluid–solid interfacial area. Therefore, quantifying the fluid–solid interfacial area can provide a way to measure wettability at the Darcy scale. Here, we experimentally explore a dual-tracer method, which can also be scaled to large geological reservoirs to quantify the fluid–solid interfacial area during the multiphase flow through a porous medium for different wetting conditions. Using our experiments, we demonstrate the influence of different saturations, wettability and flow conditions on the solid–liquid interfacial area. When oil is in the residual phase, we observe that the solid–water interfacial area increases with the increase in water saturation for the water-wet and mixed-wet cases. However, the water–solid interfacial area decreases with an increase in water saturation for the oil-wet case. We increase the water saturation by increasing the water flow rate; therefore, the anomalous behaviour seen in the oil-wet case can be attributed to the rearrangement of oil and water at higher water flow rates. When both oil and water are flowing, the solid–water interfacial area increases with water saturation for all the wettability cases and increases in water wettability as anticipated.Synopsis: Wettability measurements at Darcy-scale give a broad idea of overall subsurface wetting conditions for application in CO2 sequestration, ground-water remediation or oil recovery.

Thermal and Manufacturing Design Considerations for Silicon-Based Embedded Microchannel-Three-Dimensional Manifold Coolers—Part 2: Parametric Study of EMMCs for High Heat Flux (∼1 kW/cm2) Power Electronics Cooling

Abstract Thermal management of power electronics modules is one of the limiting factors in the peak power capability of the traction inverter system and overall efficiency of the e-drive. Liquid cooling using embedded microchannels with a three-dimensional (3D)-manifold cooler (EMMC) is a promising technology capable of removing heat fluxes of >1 kW/cm2 at tens of kPa pressure drop. In this work, we utilize computational fluid dynamics (CFD) simulations to conduct a parametric study of selected EMMC designs to improve the thermofluidic performance for a 5 mm × 5 mm heated area with the applied heat flux of 800 W/cm2 using single-phase water as working fluid at inlet temperature of 25 °C. We implemented strategies such as: (i) symmetric distribution of manifold inlet/outlet conduits, (ii) reducing the thickness of cold-plate (CP) substrate, and (iii) increasing fluid–solid interfacial area in CP microchannels, which resulted in a reduction in thermal resistance from 0.1 for baseline design to 0.04 cm2 K/W, while the pressure drop increased from 8 to 37 kPa.

Group C+ particles: Efficiency augmentation of fluidized bed reactor through nano‐modulation

AbstractGroup C+ particles, Group C particles after nano‐modulation, with extremely large specific surface area, have been shown to exhibit extraordinarily good fluidization quality with superiorly high bed expansion, significantly increasing gas holdup in the bed. As a first attempt, Group C+ particles were used as catalysts in a fluidized bed reactor (C‐plus FBR) to evaluate the reaction performance and were compared to that using Group A particles. C‐plus FBR could achieve a much higher reaction conversion, up to 235% of that using Group A particles. The contact efficiency for Group C+ particles is much higher, being 330% more than that for Group A particles. The greater contact efficiency is due to both larger specific surface area and higher bed expansion, providing larger gas–solid interfacial area and longer gas residence time. Conclusively, Group C+ particles with superior fluidization quality and reaction performance do have huge potential in gas‐phase catalytic reactions.

Influencing factors of the coarsening behaviors for 7075 aluminum alloy in the semi-solid state

The kinetics of microstructural coarsening for the semi-solid wrought 7075 aluminum alloy was determined. The variation of the coarsening rate constant K with the increasing liquid fractions and the corresponding coarsening mechanisms were determined for the recrystallization and partial remelting-processed sample. The effect of plastic pre-deformation on the value K was considered for equal channel angular pressing-based stain-induced melting activation-processed sample. A succinct review of the attempts to understand the various parameters involved in grain growth in this study and some similar literature was also provided. The results show that the rate of grain growth depends on the liquid content, temperatures, alloy composition and processing routes. The volume fraction of liquid influences both the liquid–solid interfacial area and the mean diffusion distance. The actual coarsening rate constant is the summation of independent solid and liquid contribution to the atoms diffusion. Three different coarsening mechanisms, viz. coalescence, inhibited Ostwald ripening and classical Ostwald ripening, are dominant for the elevated liquid fractions, respectively. A greater strain in the solid state or shearing rate in the liquid state usually leads to a lower coarsening rate for the alloys in the semi-solid state due to the facilitated nucleation–growth rate ratio. Further, the wrought aluminum alloys exhibit lower coarsening rate than the cast aluminum alloys due to the inhibited coarsening process by the intermetallic precipitates.

Experimental study on the wettability of microtextured surfaces generated by the ultrasonic-assisted face turning

Surface texture technology is a useful method for controlling the wettability. In this paper, ultrasonic-assisted face turning is implemented to create a microscaled texture on the flat faces. The effect of process parameters on the wettability of untextured and textured patterns is investigated by the full factorial method. Experimental results showed that the ultrasonic-assisted face turning is an effective method to create microdimples (periodic ripples) on the flat faces. Considered factors are turning (cutting speed, feed) and ultrasonic (vibration direction and vibration amplitude) parameters, which control the configuration and dimensions of microstructures. Surfaces machined by ultrasonic-assisted face turning have more liquid–solid interfacial areas compared with those processed by conventional turning. By changing the process parameters, expansion of microdimples in the cutting direction changes, hence the ratio between the interfacial and projected area and adsorption between the surface and water increases. So, textured surfaces by the ultrasonic-assisted face turning have better wettability performance in comparison to the untextured surfaces.

Ion exchange of zeolite membranes by a vacuum ‘flow-through’ technique

Ion exchange of nanoporous (e.g., zeolite) membranes is of increasing importance in their applications as separation devices and catalytic reactors. Ion exchange processes in zeolite membranes are significantly limited by slow hydrated-ion transport rates and the low liquid–solid interfacial area available in comparison to ion exchange of zeolites in powdered form, thereby leading to long membrane processing and regeneration times. Here, we consider ion exchange processes in zeolite membranes in more detail, and show the much higher efficacy of a vacuum-assisted liquid–vapor ‘flow-through’ method in comparison to both the conventional ‘immersion/counter-diffusion’ method as well as a liquid–liquid flow-through method. Na-MFI zeolite disk membranes, made by both in situ and seeded growth, were ion-exchanged with Ga3+, Zn2+, and Pt2+ ions in the temperature range of 23–70°C and exchange times of 5–24h. The penetration of these ions into the zeolite membranes was investigated in detail by energy-dispersive X-ray (EDX) spectroscopy. Surprisingly, the quantity of exchanged ions in the membranes via the vacuum-assisted ‘flow-through’ technique is found to exceed that achieved by the other two methods by up to a factor of ten, with the liquid–liquid technique being the least efficient. Higher temperatures and longer ion exchange times increased the ion exchange efficiency in the vacuum-assisted method. Chemical analysis of the condensed permeate solution by inductively-coupled plasma (ICP) mass spectrometry revealed that both the original Na+ and replacement metal cations moved through the membrane in a co-current manner, unlike the conventional counter-current movement of ions in the immersion process. The Na+ ions in the membrane experience pressure-driven transport (along with water molecules) to the permeate side, and leave the membrane surface as hydrated vapor-phase cations, thereby allowing the maintenance of a high driving force for ion exchange. In contrast, the conventional counter-current flow technique leads to a decreasing concentration driving force with time. The liquid–liquid method, even though having the same ion concentration and applied pressure driving force as the liquid–vapor method, is very slow because of the large osmotic gradient opposing the permeation of ions and water from the feed to the permeate side. The liquid–vapor ion exchanged MFI membranes showed excellent integrity (as determined by H2 and CO2 permeation measurements).

Quantifying soil physical condition based on soil solid, liquid and gaseous phases

Soil is a three-component system comprised of solid, liquid, and gas phases distributed in a complex geometry that creates large solid–liquid, liquid–gas, and gas–solid interfacial areas. Three soil phase index (TSPI) was developed to characterize the physical condition of a medium-textured soil based on solid, liquid, and gaseous phases by utilizing the concept of diminishing marginal productivity expressed in the Cobb–Douglas (C–D) production function. The index was defined as TSPI=[(Xs−C) XlXg]N. Where C and N are the constants for a given soil, X is volumetric proportion of the soil phases, the subscripts S, L, and G denote solid, liquid and gaseous phases, respectively. The use of TSPI is exemplified with soils under a series of tillage and traffic practices. To evaluate this new concept, the effects of machinery compaction on TSPI values were compared to selected credible methods for characterizing compaction effects on soil structure. A strong positive relationship was observed. TSPI had a significant relationship with selected soil properties, such as bulk density, oxygen diffusion rate, redox potential, and grain yield which were measured in a field experiment reported in the literature. Furthermore, the correlation of TSPI and the soil physical parameter S which is defined as the slope of the soil water retention curve at its inflection point was investigated and a significant linear relationship was also found for soil with given water contents. Overall, the primary advantage of TSPI is that it allows characterizing and evaluating the effects of management practices (e.g., tillage and/or traffic) on the three soil phase condition. Additional testing is needed to evaluate the utility of the index for predicting soil productivity under a wide range of conditions.

Controllable synthesis of 3D NiχCo1−χ oxides with different morphologies for high-capacity supercapacitors

3D NiχCo1−χ oxides with different morphologies for high-capacity supercapacitors were controllably synthesized via an electrodeposition method combined with a simple post annealing process. The synthesis involves the co-electrodeposition of the bimetallic (Ni, Co) hydroxide precursor on a nickel foam scaffold and subsequent thermal transformation to NiχCo1−χ oxides. The crystalline structure, morphology and electrochemical performance of the 3D NiχCo1−χ oxides can be readily manipulated by simply varying the Co/Ni molar ratio in the electrodeposition electrolyte. With the increase of the Co/Ni molar ratio, the characteristic peak intensities and the signal sites were gradually changed from a NiO crystal dominant structure to NiCo2O4 and finally to a Co3O4 dominant structure. Moreover, the morphology also can be controlled by adjusting the Co/Ni molar ratio in the electrodeposition electrolyte. In addition, the Ni0.61Co0.39 oxide electrode shows a large specific capacitance of 1523.0 F g−1 at 2 A g−1 and 95.30% of that can be retained, even at a high current density of 30 A g−1. The superior rate capability should be attributed to the unique 3D network-like architecture, which can enlarge the liquid–solid interfacial area, facilitate the electron and ion transport, and further increase the utilization of the active material. To demonstrate its practical application, an asymmetric supercapacitor based on the Ni0.61Co0.39 oxide electrode as a positive electrode and activated carbon as a negative electrode was fabricated. Owing to the outstanding capacitive behavior of the Ni0.61Co0.39 oxide electrode, the asymmetric device delivers a prominent energy density of 36.46 W h kg−1 at a power density of 142 W kg−1, and which holds great promise for potential applications in energy storage.

Effect of foam stirrer design on the catalytic performance of rotating foam stirrer reactors

The liquid–solid mass transfer rate in a rotating foam stirrer reactor and in a slurry reactor is studied using the hydrogenation of styrene as a model reaction. The rotating foam stirrer reactor is a novel type of multi-phase reactor where highly open-celled materials, solid foams, are used as a catalyst support and as a stirrer. The design of the foam stirrer has a strong influence on the liquid–solid mass transfer rate. Using a donut-shaped foam block configuration, the liquid solid mass transfer coefficient, kLS, is five times lower than in a blade configuration. The reduced liquid circulation through the foam block structure is explained by a higher frictional pressure drop. The pore Reynolds number indicates that the flow is in the laminar regime for the foam block stirrer while it is turbulent for the blade stirrer. Local measurements of kLS indicate a mass transfer profile along the height of the foam block structure, allowing a pertinent choice of the catalyst location within the foam block and/or suggesting changes of the foam block design to avoid the bottom effects, for instance, using a conical foam block shape. However, the foam block stirrer offers higher liquid–solid interfacial area than a blade stirrer, resulting in higher kLSaLS. At a power input above 1000W/mL3 and using a 20ppi foam block with the top part catalytically active, the reaction rate is not liquid–solid mass transfer limited. Compared to a Rushton stirrer, the liquid–solid mass transfer rate is enhanced because of a high liquid–solid interfacial area and a fast refreshment of the catalyst surface. kLSaLS values of 0.5s−1 are obtained compared to 0.04s−1 for the slurry system. The same production rate as in the slurry reactor is achieved using 62% less catalyst. As the catalyst is immobilized on the stirrer, an additional advantage of the rotating foam stirrer reactor is the absence of a catalyst separation step. Attrition and agglomeration of the catalyst do not occur and the foam catalyst can be reused.

CoxNi1−x double hydroxide nanoparticles with ultrahigh specific capacitances as supercapacitor electrode materials

Cobalt nickel double hydroxides (CoxNi1−x LDHs) nanoparticles were synthesized by a polyvinyl pyrrolidone-assisted chemical co-precipitation method. It was found that the ratio between Co and Ni had a significant effect on their electrochemical activities. The specific capacitance of 2614Fg−1 was achieved when the atomic ratio of Co to Ni was equal to 0.57:0.43. This Co0.57Ni0.43 LDH sample had a BET specific surface area of 109.8m2g−1 and total pore volume of 0.6036cm3g−1, and its pore size distribution was mainly in the range of 1.5–5 nm, which led to the high liquid–solid interfacial area and further increased the utilization of the active materials. Additionally, the Co0.57Ni0.43 LDH electrode exhibited a good electrochemical stability with 86.4% of the initial capacitance over 1000 consecutive cycles at 5Ag−1.

An improved bounce-back scheme for complex boundary conditions in lattice Boltzmann method

In recent years, the lattice Boltzmann method (LBM) has been widely adopted to simulate various fluid systems, and the boundary treatment has been an active topic during the LBM development. In this paper, we present a novel approach to improve the bounce-back boundary treatment for moving surfaces with arbitrary configurations. We follow the framework originally proposed by Ladd [A.J.C. Ladd, Numerical simulations of particulate suspensions via a discretized Boltzman equation. Part 1. Theoretical foundation, Journal of Fluid Mechanics 271 (1994) 285–309]; however, the adjustment in the density distribution during the bouncing-back process at the boundary is calculated using the midpoint velocity inter-/extrapolated from the boundary and fluid velocities, instead of the real boundary velocity in the Ladd method. This modification ensures that the bouncing-back process and the density distribution adjustment both take place at a same location: the midpoint of a boundary lattice link, and thus removes the discrepancy of bouncing-back at the midpoint but density distribution adjustment at the boundary point in the original Ladd method. When compared with other existing boundary models, this method involves a simpler algorithm and exhibits a comparable or even better accuracy in describing flow field and flow-structure interaction, as demonstrated by several test simulations. Therefore, this boundary method could be considered as a competitive alternative for boundary treatment in LBM simulations, especially for particulate and porous flows with large fluid–solid interfacial areas.

Liquid−Solid Mass Transfer and Reaction in a Rotor−Stator Spinning Disc Reactor

The heterogeneously catalyzed oxidation of glucose is performed in a rotor−stator spinning disk reactor. One side of the rotor is coated with a Pt/C and Nafion catalytic layer, resulting in a liquid−solid interfacial area of 274 mi2 mR−3. At the lowest rotational disk speed, 26 rad s−1, the reaction is liquid−solid mass transfer limited; at the highest rotational disk speed, 180 rad s−1, the intrinsic kinetics are rate determining. The experimental overall reaction rates are fitted with a resistances in series model, with the activation energy, pre-exponential factor, and volumetric liquid−solid mass transfer coefficient as parameters. The volumetric liquid−solid mass transfer coefficient, kLSaLS, increases from 0.02 to 0.22 mL3 mR−3 s−1 for a rotational disk speed of 26 to 157 rad s−1. These values are high in comparison to conventional reactors, like packed beds, in spite of the low liquid−solid interfacial area used in this study. The values of the liquid−solid mass transfer coefficient kLS are 1 order...

Three-dimensional analysis of trickle flow hydrodynamics: Computed tomography image acquisition and processing

Computed tomography (CT) is a powerful technique that can be used to image multi-phase flow in three dimensions. In this study, X-ray CT is used to image trickle flow in a stationary packed bed with a spatial resolution of 118 μ m / pixel . Errors introduced during the radiograph acquisition and tomographic reconstruction of the volume image make it difficult to identify the three phases (gas, liquid and solid) and in particular the interfacial areas. A novel post-processing strategy based on the matrix convolution operation and a priori knowledge of the shape of the particles is developed that makes it possible to accurately identify the phase interfaces in an unbiased way. The result is a ternary three-dimensional image where each voxel is one of gas, liquid or solid. From this, the gas–liquid, gas–solid and liquid–solid interfacial areas can be calculated. The proposed procedure yields images that are superior to those obtained from the usually employed thresholding operation.

HdPro: a mathematical model of trickle-bed reactors for the catalytic hydroprocessing of oil feedstocks

A steady-state model for trickle-bed reactors was developed, primarily concerning hydroprocessing of light oil feedstocks containing volatile compounds. The case of a homogeneous plug flow fixed bed reactor with axial dispersion was considered. Catalyst particles were assumed to be isothermal and isoconcentrational. Mass balances, overall two-phase flow momentum balance and phase energy balances were written in detail. Hydrodynamic flow of the two phases and specifically the flow regime under which the bed was operated, the liquid holdup, the wetting efficiency of the solid particles, the two-phase flow pressure drop and the gas–liquid and liquid–solid interfacial areas were all predicted using carefully selected industrial engineering correlations. In addition, all necessary thermophysical properties, such as phase densities, viscosities, conductivities, diffusivities, interfacial tension, latent heats of vaporization, specific heats, and molar partial enthalpies were continuously calculated as functions of the system pressure, temperature and phase composition. A suitable numerical package was developed for this kind of calculations. Phase equilibrium was calculated with the aid of the same package and the non-ideal phase behavior was taken into account, as well. Mass transfer rates were calculated by the effective diffusivity method. Compared to a set of experimental data taken from the operation of a pilot scale hydrodesulfurization plant, excellent agreement was found. A user-friendly interface was developed to facilitate the use of the numerical package.

Liquid Flow Texture in Trickle-Bed Reactors: An Experimental Study

Modeling of trickle-bed reactors requires the knowledge of liquid flow texture. A dye-adsorption method was employed to study the liquid flow texture in the bed. Pictures of cross sections of the dismantled bed at different depths were taken. The texture in prewetted and nonprewetted beds of glass beads (nonporous) and alumina particles (porous) of different sizes was studied. To supplement the visual observation, exit liquid distribution and pressure drop were measured. The liquid flow texture was deduced from the visual observations and exit liquid distribution. The present study revealed several unexpected features. The behavior of a bed of porous particles was strikingly different from that of nonporous particles. The interpretation of the previous work on the hysteresis of pressure drop, gas−liquid and liquid−solid interfacial areas, and the implications of the observed liquid flow texture on modeling of trickle-bed reactors are discussed.