Packing Contact Research Articles

Exploration of the adsorption and desorption performance of volatile organic compounds by activated carbon with different shapes based on fixed-bed experiments

Activated carbon (AC) has been widely used in volatile organic compounds (VOCs) treatment of industrial exhaust gases. Rather than modifying specific pore size distributions and surface properties, altering the shape of AC offers a more feasible approach to enhance its adsorption performance. This study investigates the adsorption-desorption performance of two different shaped ACs with highly similar properties for the removal of VOCs. The clover-shaped AC (CSAC) has a 27.46% lower internal void fraction and a 39.10% higher external void fraction compared to cylindrical AC (CAC), resulting in denser packing and longer contact time with VOCs. Adsorption experiments showed the CSAC has 40% longer adsorption breakthrough (BT) times for ethanol, ethyl acetate, and n-hexane on average, and 20% higher saturation adsorption capacity per unit volume. CSAC also has higher partition coefficients, with the highest values for ethanol, ethyl acetate, and n-hexane being 0.0187, 0.0382, and 0.0527 mol kg−1·Pa−1, respectively. The desorption process for selected VOCs is non-spontaneous and endothermic. Optimal desorption conditions were identified as an inlet space velocity of 3535 h−1, a desorption temperature of 150 °C, and a pulsed inlet method. To investigate the possibility of the application of CSAC in real-world scenarios, xylene was chosen as a representative industrial VOC. Results showed CSAC has 20% higher BT time and saturation adsorption capacity for xylene compared to CAC under different bed heights. The desorption efficiency for xylene on both ACs is below 40%. With increasing xylene inlet concentration, the mass transfer zone (MTZ) height initially increases but stabilizes beyond 1704 mg m−3. At identical bed heights, the MTZ height of CSAC is 29% shorter than CAC, indicating a higher bed utilization efficiency.

Exploring the role of particle-form polydispersity in the fabric of granular packing: Insights from DEM simulations with ellipsoidal particle assemblies

Granular materials, such as sand, exhibit a wide range of particle sizes and shapes, known as polydispersity. This study aims to investigate the effects of particle-form (first-level approximation of particle shape) polydispersity on a fabric of granular packing using DEM simulations of ellipsoidal particle assemblies. A framework for DEM simulations is proposed to investigate the particle-form polydispersity, and an overall polydispersity index (OPI) is introduced to quantify its magnitude. Various parameters are employed to quantify the fabric, including packing density, coordination number, contact force, and fabric anisotropy. The results highlight that the particle-form polydispersity notably affects the packing density and mean coordination number of the granular packings. Furthermore, a prediction model for the packing density and mean coordination number of polydisperse packings is proposed based on the correlations fitted from the monodisperse packing data.

Numerically investigation of the neutron irradiation swelling on the mechanical and structural evolution of beryllium pebble bed

Pebble bed is employed in the blanket system to achieve neutron multiplication and tritium breeding. Neutron irradiation among the pebble bed is inevitable when the tokamak device is in normal operation. Particles could be swelled and the formation of bubbles or pore on the surface could aggravate the roughness of particles the surface under irradiation. It has great impact of pebble bed structure. In this paper, the mechanical and structure characteristics of the Beryllium (Be) pebble bed in the Helium Coolant Ceramic Breeding (HCCB) blanket were investigated. Furthermore, the evolution process of the pebble bed with mesoscale is analyzed as well. The Discrete Element Method (DEM) with Particle Flow Code (PFC) software is utilized to simulate the variation of particles under neutron irradiation with different roughness of particle surfaces and irradiation doses. Meanwhile, 0, 1%, 2%, 4% and 6% irradiation of single particle in radius direction with 0, 0.1, 0.3 and 0.5 friction coefficients were assumed. The evolution of the local packing factor, coordination number, contact force and force chain are given, and the fabric analysis is also given. The results show that the irradiation swelling of the particles and the deterioration of the surface have great impacts on the structure and mechanical properties of the pebble bed under neutron irradiation. Particle swelling could improve the packing factor and coordination number of the pebble bed, and the contact force distribution. The deterioration of the particle surface reduces the coordination number and shortens the force chain length. This paper presents the working condition under neutron irradiation which could provide reference for the design and evaluate of the blanket pebble bed.

Relative Kinetics of Solid-State Reactions: The Role of Architecture in Controlling Reactivity.

Countless inorganic materials are prepared via high temperature solid-state reaction of mixtures of reagents powders. Understanding and controlling the phenomena that limit these solid-state reactions is crucial to designing reactions for new materials synthesis. Here, focusing on topotactic ion-exchange between NaFeO2 and LiBr as a model reaction, we manipulate the mesoscale reaction architecture and transport pathways by changing the packing and interfacial contact between reagent particles. Through analysis of in situ synchrotron X-ray diffraction data, we identify multiple kinetic regimes that reflect transport limitations on different length scales: a fast kinetic regime in the first minutes of the reaction and a slow kinetic regime that follows. The fast kinetic regime dominates the observed reaction progress and depends on the reagent packing; this challenges the view that solid-state reactions are necessarily slow. Using a phase-field model, we simulated the reaction process and showed that particles without direct contact to the other reactant phases experience large reduction in the reaction rate, even when transport hindrance at particle-particle contacts is not considered.

Classification of the Packing Contact Elements of Mass-Exchange Towers with Second-Order form of the Surfaces (Survey of Patents)

Classification of the Packing Contact Elements of Mass-Exchange Towers with Second-Order form of the Surfaces (Survey of Patents)

A recurring packing contact in crystals of InlB pinpoints functional binding sites in the internalin domain and the B repeat.

InlB, a bacterial agonist of the human receptor tyrosine kinase MET, consists of an N-terminal internalin domain, a central B repeat and three C-terminal GW domains. In all previous structures of full-length InlB or an InlB construct lacking the GW domains (InlB392), there was no interpretable electron density for the B repeat. Here, three InlB392 crystal structures in which the B repeat is resolved are described. These are the first structures to reveal the relative orientation of the internalin domain and the B repeat. A wild-type structure and two structures of the T332E variant together contain five crystallographically independent molecules. Surprisingly, the threonine-to-glutamate substitution in the B repeat substantially improved the crystallization propensity and crystal quality of the T332E variant. The internalin domain and B repeat are quite rigid internally, but are flexibly linked to each other. The new structures show that inter-domain flexibility is the most likely cause of the missing electron density for the B repeat in previous InlB structures. A potential binding groove between B-repeat strand β2 and an adjacent loop forms an important crystal contact in all five crystallographically independent chains. This region may represent a hydrophobic `sticky patch' that supports protein-protein interactions. This assumption agrees with the previous finding that all known inactivating point mutations in the B repeat lie within strand β2. The groove formed by strand β2 and the adjacent loop may thus represent a functionally important protein-protein interaction site in the B repeat.

Effects of fixed wall and pebble size ratio on packing properties and contact force distribution in binary-sized pebble mixed beds at the maximum packing efficiency state

The binary-sized pebble mixed beds at the maximum packing efficiency state were numerical simulated by the DEM simulation to investigate the effect of fixed wall and pebble size ratios. The evolution of the distribution of packing fraction and porosity, radial distribution function and contact force were given and analyzed with emphasis on the effects of the fixed wall and pebble size ratio. The results showed that the fixed wall will result in a reduction of average packing fraction and an obvious wall effect in local porosity distribution. With the increase of the pebble size ratio, the volume fraction of the wall affected regions gradually decrease. The variation of the local packing fraction of the binary-sized pebble bed is mainly determined by the partial packing fraction of large pebbles and the partial packing fraction of small pebbles, respectively, in the regions close to the fixed wall. Furthermore, the fixed wall has little effect on the radial distribution function and contact force. However, the pebble size ratios have great influence on the radial distribution function and the contact force in binary-sized pebble bed at the maximum packing efficiency state. With the increase of the pebble size ratio, the radial distribution functions of the whole pebble beds are consistent with that of small pebbles, and approach to that of the mono-sized pebble bed. In addition, with the increase of the pebble size ratio, a higher contact force can be obtained in pebble beds.

Effect of Pebble Size Distribution and Wall Effect on Inner Packing Structure and Contact Force Distribution in Tritium Breeder Pebble Bed

In the tritium breeding blanket of nuclear fusion reactors, the heat transfer behavior and thermal-mechanical response of the tritium breeder pebble bed are affected by the inner packing structure, which is crucial for the design and optimization of a reliable pebble bed in tritium breeding blanket. Thus, the effect of pebble size distribution and fixed wall effect on packing structure and contact force in the poly-disperse pebble bed were investigated by numerical simulation. The results show that pebble size distribution has a significant influence on the inner packing structure of pebble bed. With the increase of the dispersion of pebble size, the average porosity and the average coordination number of the poly-disperse pebble bed gradually decrease. Due to the influence of the fixed wall, the porosity distribution of the pebble bed shows an obvious wall effect. For poly-disperse pebble bed, the influenced region of the wall effect gradually decreases with the increase of the dispersion of pebble size. In addition, the gravity effect and the pebble size distribution have an obvious influence on the contact force distribution inside the poly-disperse pebble bed. The majority of the contact force are weak contact force that is less than the average contact force. Only a few of pebbles have strong contact force that is greater than average contact force. This investigation can help in analyzing the pebble crushing characteristics and the thermal hydraulic analysis in the poly-disperse tritium breeder pebble bed.

Analysis and prediction of the tensile strength of aluminum alloy composite using statistical and artificial neural network technique

In this research work, aluminum alloy (Al-20Fe-5Cr) matrix-based aluminum oxide (Al2O3) reinforced composites were developed through the powder metallurgy (P/M) process. Effect of compaction pressure (200, 250 & 300 MPa) and wt.% of Al2O3 (0, 10, 20 & 30 wt.) on tensile strength and percentage elongation has been analyzed through statistical and artificial neural network techniques (ANN). The mixture of Al-alloy powder particles and Al2O3 particles were synthesized in a centrifugal ball mill for 20 min. Compaction of synthesized powder was carried in the standard tensile die using a uniaxial hydraulic pressing machine. Sintering was performed at temperature 580 ± 20 °C for one hour in an argon gas environment using an electric tubular furnace. It was found that tensile strength enhanced significantly with the addition of Al2O3up to 20 wt.% and then declined sharply for the 30 wt.% of Al2O3at all compaction pressures. The highest tensile strengths were found for each wt.% of Al2O3 at compaction pressure 300 MPa compare to other compaction pressures. Tensile strength increased from 105 to 158 MPa with the addition of 20 wt.% Al2O3 and decreased to 142 MPa for 30 wt.% at 300 MPa compaction pressure. The improvement resulted from better compaction, leading to more plastic deformation, better packing, and high effective contact area. However, the percentage of elongation decreased from 23.2% to 2.2% with an increment of wt.% of Al2O3 for compaction pressure 200 MPa, while for 300 MPa, its value drops from 25.8% to 6.5%. This depreciation can be reasoned for the reduction in ductile matrix content and dilute flowability of the Al matrix, which occurred due to brittle Al2O3. The statistical analysis using ANOVA revealed that the compaction pressure is the primary control factor influencing tensile strength by 90.3%. The feed-forward network with a back-propagating gradient-descent error minimization training approach and mean squared error (MSE) as performance function was employed to model and predict tensile strength. The developed 3-layered multilayer perceptron (MLP) with 2–10–2 network architecture established a correlation between the inputs and outputs with minimum error (MSE) below 1% and maximum correlation coefficient (R) close to 1.

3D shape quantification and random packing simulation of rock aggregates using photogrammetry-based reconstruction and discrete element method

Rock aggregates are commonly used granular material in building engineering. The 3D reconstruction of realistic rock aggregates is significant for the study of their mechanical properties in numerical simulation. This paper aims to create an efficient particle reconstruction system and analyse the effects of particle shapes on the random packing properties of rock aggregates. First, a photographic system is established to obtain 2D images of rock aggregates from multiple shooting directions, and the photogrammetric technology is employed to reconstruct the 3D model of the rock aggregate. A total of 1000 realistic 3D models of rock aggregates are obtained. Second, four shape indexes, i.e., elongation index (EI), flatness index (FI), convexity index (CI), and roundness (RD), are employed to characterize the shapes of the obtained rock aggregates. The results of statistical analysis show that the probability distribution of rock aggregates’ shape indexes can be well fitted by Gaussian function. Third, the initial samples with different EI and FI values are generated through a series of computational algorithms based on MATLAB and then are imported into PFC3D for discrete element simulation. Subsequently, random packing of rock aggregates is carried out by two different methods, i.e., the gravity falling method (GFM) and the isotropic compression method (ICM). The results show that the EI and FI have significant influences on packing density, coordination number, fabric anisotropy, and contact force between the samples.

Analysis of the Performance Improvement Effect of Combined Packing for Oil and Gas Well Packer

Packer is a commonly used downhole tool for oil and gas wells. In order to understand the working performance of combined packing, a finite element analysis is performed on the double expansion-compression-expansion combined seal packers to find the effect of combined seal. Taking packers sealed in casing with a diameter of 114.3mm and a wall thickness of 12.7mm as an example, finite element models are established for double expansion and expansion-compression combined seal packers respectively. By applying packer-setting pressure to the finite element models and processing the strain-stress data resulting from finite element analyses, the distribution rules of packing stress and contact pressure between the packing and the inner casing wall for different combined seal packers are obtained. The working performance of the single expansion seal packer and the double expansion and expansion-compression combined seal packers is compared and analyzed. According to the results of finite element analyses, both double expansion combined seal and expansion-compression combined packings can be in effective contact with the casing under a packer-setting pressure of 15MPa, and the contact pressure between the combined seal packing and the inner casing wall is larger than that of a single seal packing. The combined seal packer therefore can actually improve the sealing and packoff effect of the packer. The expansion-compression combined seal has the highest pressure bearing capacity, which is 50% higher than that of the single expansion packer. The lower packing of the double expansion combined packer and the expansion packing of the expansion-compression combined seal packers should be appropriately strengthened and thickened to improve the packing performance of the combined seal packer. The results of contrastive analysis reveal the improvement effect of the sealing and packoff performance of the combined seal packers, which can be used as a reference for the improved design of such packer.

Automatic control system for operation modes and calibration of technological parameters of evaporation cooling apparatuses

The paper provides the scheme and algorithm of the automatic system controlling the operation modes of evaporation cooling apparatuses for industrial recirculating water of local recirculating water supply systems. The authors have described the principle of parameter registration and the automatic calibration of the main parameters at the commissioning stage and during the operation of heat and mass transfer technological equipment. The authors have developed a new approach to the use of elastically deformable heat and mass transfer packing blocks and wastes from metalworking machines as packing contact devices for evaporation cooling apparatuses. Compressed blocks of metal shavings can be volumetrically elastically deformed which allows adjusting operation modes automatically and solving partly a very serious problem of disposing industrial wastes from machine-building enterprises. The article also covers developing of evaporation cooling apparatuses.

Systematic profiling of staralog response to acquired drug resistant kinase gatekeeper mutations in targeted cancer therapy.

Kinase-targeted therapy has been widely used as a lifesaving strategy for cancer patients. However, many patients treated with targeted cancer drugs are clinically observed to rapidly develop acquired resistance. Kinase gatekeeper mutation is one of the most chief factors contributing to the resistance, which modulates the accessibility of kinase's ATP-binding pocket. Previously, the pan-kinase inhibitor Staurosporine and its analogs (termed as Staralogs) have been reported to exhibit wild-type sparing selectivity for some kinase gatekeeper mutants, such as EGFR T790M, Her2 T798M and cSrc T338M. Here, we describe an integrative approach to systematically profile the molecular response of 15 representative Staralogs to 17 kinase gatekeeper mutations in targeted cancer therapy. With the profile we are able to divide gatekeeper mutations into three classes (i.e. classes I, II and III) and to divide Staralogs into two groups (i.e. groups 1 and 2) using heuristic clustering. The class I and II mutations confer consistent sensitivity and resistance for all Staralogs, respectively, while the class III mutations address divergent effects on different Staralogs. The mutations to Ile residue can generally reduce Staralog affinity by inducing unfavorable steric hindrance, whereas the mutations to Met and Leu residues would improve Staralog affinity by establishing favorable S···π interaction, van der Waals packing and/or hydrophobic contact. The group 1 and 2 Staralogs are primarily determined by carbonyl or hydroxyl substitution state at the position 7 of Staralog core, where points to kinase gatekeeper residue and can thus be directly influenced by gatekeeper mutation.

In Situ X-ray Tomography and 3D X-ray Diffraction Measurements of Cemented Granular Materials

In situ x-ray tomography and three-dimensional (3D) x-ray diffraction analysis have been combined to investigate the mechanical behavior of noncemented and lightly cemented quartz particles under quasistatic confined uniaxial compaction. The motivation for this study is to understand the particle-scale origin of the mechanical behavior of cemented particulate materials and to isolate what makes this behavior distinct from that of noncemented particulate materials. Tomography measurements elucidated the particle packing structure, contact fabric, cementation, and particle fragmentation, while 3D x-ray diffraction measurements provided insight into particle rotations and particle-resolved strain and stress tensors. The cemented sample was found to exhibit higher resistance to individual particle fragmentation and significantly restrained particle motion, compared with the noncemented sample, likely due to the cement bridges between particles. This reduction in particle fragmentation and motion may explain the significantly enhanced macroscopic stiffness of the cemented sample, as well as the strong alignment of intraparticle principal stresses with the macroscopic strain direction. These findings advance particle-scale understanding of cemented granular media and provide motivation for further research focused on developing fundamental understanding of the constitutive response of these materials.

Experimental plant for studying hydrodynamics and heat and mass exchange processes in packing contact devices

The paper provides a description of the developed experimental plant for studying hydrodynamic and heat and mass exchange processes in packing devices of all kinds of configuration, examples of the obtained data and original classification methods for processing experimental data. The authors describe hydrodynamic characteristics allowing carrying out classification studies and obtaining the necessary data to complete the developed methods for calculating mass exchange devices: the retaining capacity of packing devices at liquid and gas phases in particular. The authors provide the criteria function X=f(Rem) which gives a direction for industrial application of packing contact devises. The function is based on the analysis and generalization of the experimental data obtained in express studies of single-phase filtration curves. The paper also covers an example of the experimental data of the response function in case of recognizing flow structures of contact phases which allow obtaining necessary data to complete the developed diffusion models of mass exchange processes and implement calculations of mass exchange packing with a high precision.

In situ investigation of stress-induced martensitic transformation in granular shape memory ceramic packings

Stress-induced martensitic transformation can occur in granular shape memory materials when individual particles experience high stresses and transform from a high-symmetry austenite phase to a low-symmetry martensite phase. This involves a highly heterogeneous distribution of the driving force and very low mechanical constraint for martensite nucleation, so the transformation behavior can be dramatically different from the well-documented case of monolithic solids. In this work, we investigate the stress-induced martensitic transformation in granular shape memory ceramic packings, which consist of single-crystal micro-particles of ZrO2-12 at%CeO2 and ZrO2-15 at%CeO2. Through in situ neutron diffraction, we study how the phase fraction, lattice strain, and integral peak broadness evolve during external loading, unloading, and subsequent heating. Several peculiar features are discovered, including (i) a continuous mode of transformation with a wide range of transformation loads, (ii) co-evolution of the packing structure, contact deformation, and martensitic transformation, and (iii) a strong correlation between the peak broadening and the transformed phase fraction. In addition, we show the first direct evidence of reversible stress-induced martensitic transformation in granular materials. We finally discuss the mechanism for martensite nucleation and growth in granular packings and show how that leads to the observed transformation characteristics.

A fast adhesive discrete element method for random packings of fine particles

Introducing a reduced particle stiffness in discrete element method (DEM) allows for bigger time steps and therefore fewer total iterations in a simulation. Although this approach works well for dry non-adhesive particles, it has been shown that for fine particles with adhesion, system behaviors are drastically sensitive to the particle stiffness. Besides, a simple and applicable principle to set the parameters in adhesive DEM is also lacking. To solve these two problems, we first propose a fast DEM based on scaling laws to reduce particle Young’s modulus, surface energy and to modify rolling and sliding resistances simultaneously in the framework of Johnson-Kendall-Roberts (JKR)-based contact theory. A novel inversion method is then presented to help users to quickly determine the damping coefficient, particle stiffness and surface energy to reproduce a prescribed experimental result. After validating this inversion method, we apply the fast adhesive DEM to packing problems of microparticles. Measures of packing fraction, averaged coordination number and distributions of local packing fraction and contact number of each particle are in good agreement with results simulated using original value of particle properties. The new method should be helpful to accelerate DEM simulations for systems associated with aggregates or agglomerates.

Ring Packing Contact Elements of Mass Transfer Devices (review of patents)

A classification of the ring packing contact components of heat and mass transfer devices, the chief example of which is the Raschig ring, is proposed. Examples of designs of domestically produced and foreign unordered and ordered ring packing contact components along with their advantages and drawbacks are considered.

Effect of number of granulometric fractions on structure and micromechanics of compressed granular packings

The role of number of grain size fractions on structural and mechanical properties of uniaxially compressed granular packings with a uniform particle size distribution in terms of number of particles and with various particle size dispersities was studied using the discrete element method. The study addressed packing density, coordination number, contact forces, global stress, and energy dissipation in assemblies composed of frictional spheres. Packing density was found to change with increasing number of granulometric fractions in mixtures with a small ratio of the diameters of the largest to smallest particles. Results indicated a certain value of particle size ratio below which the number of particle size fractions strongly affected packing density. The average coordination number decreased with increasing number of fractions. Detailed analysis of the effect of particle size dispersity on mechanical coordination number, including particles with no less than four contacts, revealed that, contrary to the average coordination number, the mechanical coordination number increased with increasing ratio of the diameters of the largest to smallest particles in the sample. The composition of polydisperse samples strongly affected stress distribution and energy dissipation in granular packings.

New 3D-stereoconfigurated cis-tris(fluorenylphenylamino)-benzene with large steric hindrance to minimize π–π stacking in thin-film devices

Highly fluorescent trans- and cis-tris(fluorenylphenylamino)benzene stereo-isomeric derivatives, trans- and cis-tris(DPAF-C9), respectively, were designed and synthesized to minimize facile planar fluorene ring stacking in the solid state during thin-film device fabrications. Resulting tris-cup cis- and tris-chair trans-conformers were hypothesized to be capable of reducing direct packing contact of light-harvesting fluorene moieties from each other that should reduce the aggregation-related self-quenching effect derived from the π–π stacking packing arrangement. By the fact of closely matching photophysical characteristics of them to those of poly(N-vinylcarbazole) (PVK), we applied the former conformer as the secondary blue hole-transporting material in the study of its electroluminescence properties, using a tricomponent system of PVK‒cis-tris(DPAF-C9)‒tris(2-phenylpyridine)iridium (III) [Ir(ppy)3], as an example. Accordingly, several prototype single-layered or multilayered devices were fabricated with their electroluminescence and external quantum efficiency demonstrated. These analogous 3D-stereoconformers can also be used in other fluorescence-related thin-film applications.