Selected Operations Involving Transport of a Single Fluid Phase through a Porous Medium

Dullien, F. A. L.

doi:10.1016/b978-0-12-223651-8.50010-9

Cited by 5 publications

(4 citation statements)

References 19 publications

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“…its liquid diffusion behavior and swelling mechanisms . The porosity of the SAP (e.g., open or closed pores) is known to influence liquid diffusion, where open pores have been shown to give a faster initial absorption than closed pores or solid structures. − Capillarity has been shown to be the main mechanism governing the initial volumetric flow of water within the porous SAP structures, ,,, where the minimization of energy due to the surface energy of the liquid, causes the liquid to move toward inner sections of the material. Laplace’s Law for capillary pressure ( C in Pa) given by where σ is the surface tension (N/m), g is the gravitational acceleration at the surface (m/s 2 ), h the height of the capillary (m), r the radius (m) and ρ is the density of the liquid (kg/m 3 ).…”

Section: Physico-chemistry Behind Liquid Absorption In a Polymermentioning

confidence: 99%

Advances in the Use of Protein-Based Materials: Toward Sustainable Naturally Sourced Absorbent Materials

Capezza

Newson

Olsson

et al. 2019

ACS Sustainable Chem. Eng.

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Superabsorbent polymers (SAPs) are important in the health-care and personal care industries. Products like bed pads and diapers improve the comfort and sanitary conditions for people all over the world, with SAPs reaching yearly production volumes of ca. 2 million tons. However, recent sustainability issues have questioned the high negative footprint of polymers from nonrenewable resources. Biomacromolecules, especially when functionalized, have properties that make them an attractive alternative for the production of biobased SAPs. Proteins are a particularly interesting alternative due to their high variability and because of their relatively low price, being available as side streams from the agricultural industries. Due to the harsh extraction conditions, these side stream proteins are not competing with the food industry and alternative source-effective uses are advantageous in a circular bioeconomy. As the properties of a SAP material come from a combination of neutralized functional groups to promote polar liquid uptake and intermolecular cross-links to prevent dissolution, proteins offer unique opportunities due to their variability in polymerization. An increased understanding of the protein characteristics and how these can be tuned through functionalization is therefore a prerequisite for the successful development of a commercial biobased SAP that utilizes industrial and nontoxic wastes toward more sustainable products. This review focuses on proteins as biomacromolecules with relevant characteristics for superabsorbent functions, and discusses the opportunities that they may offer toward sustainable SAPs utilizing nontoxic chemicals and following the green chemistry principles.

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Section: Physico-chemistry Behind Liquid Absorption In a Polymermentioning

confidence: 99%

Advances in the Use of Protein-Based Materials: Toward Sustainable Naturally Sourced Absorbent Materials

Capezza

Newson

Olsson

et al. 2019

ACS Sustainable Chem. Eng.

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“…Further classifications include empirical models, deterministic models based on Stokes flow, network models, statistical models, and flow-around-submerged-object models, among others [4]. Most of the theoretical models include an expression composed of the square of the effective diameter and a function of the porosity [5][6][7][8] Literature has a number of experimental techniques for measuring permeability. Constant pressure 1-D flow technique, constant flow rate 1-D flow method, radial flow method (point injection in 2D, line injection in 3D), etc.…”

Section: Introductionmentioning

confidence: 99%

“…where De is the effective diameter and ε is the porosity. This function of porosity 𝐹(ε) can be estimated for several models: Kezeny-Carman [3], Davies [8], Chen [7], Tomadakis and Robertson [6]. The functions for different model are listed in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Estimating the Permeability of a Porous Ceramic Tile

Hasan¹,

Borkot

Hasan

et al. 2023

Preprint

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Porous ceramics are widely used for water filtering, improving heat transfer, supporting catalysts, vaporizing liquids, etc. Residential tiles used for water sealing are made from ceramic as well. Moisture infusion analysis based on Richard's equation is necessary to improve tile quality, and this analysis depends heavily on estimating the tile permeability. The current research demonstrates three techniques for calculating ceramic-tile permeability. The first technique is a theoretical model that requires information about the material's effective diameter and porosity that was obtained via scanning electron microscopy (SEM). The second suggested technique is known as mercury intrusion porosimetry (MIP). The pore size, density, pore volume, and porosity of the ceramic tiles, among other characteristics, are evaluated using mercury in this procedure. The experiment's pressure was varied from 0.1 to 60000 psi. These criteria were used to determine the tile's permeability. The last strategy addressed in this research is the falling-head permeameter (FHP) approach. This procedure involves inserting the specimen into a sealed transparent rectangular conduit. Water is then allowed to pass through it. The rate at which the water level in the duct recedes over time is associated with permeability. All the approaches yield permeability values that are in the same order-of-magnitude of 10 -16 m 2 .

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“…The value of suction at the 'inflexion-point' (SWRC dry-IP) can be considered as the 'breakthrough' matrix potential at which air penetrates through the soil (White et al, 1970;Dullien, 1992). Particles are rearranged in a more compact distribution pattern, that is to say, close to the residual void ratio level.…”

Section: Stage-3-d (Aev To 'Dry-ip'/'sl')mentioning

confidence: 99%

Experimental and numerical analysis of the unsaturated soil shrinkage and swelling behaviour under different compaction conditions

Najdi

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(English) The thesis presents part of an ongoing nvestigation on the Thermo-Hydro-Mechanical (THM) behaviour and cracking of deformable unsaturated soils undergoing cycles of drying and wetting. An experimental approach was first adopted to understand the principal mechanisms of the THM behaviour. A main principal variable is the negative porewater pressure (suction). Suction is an essential component for the constitutive relations. Direct measurements at high suction range is only possible to this date using High Capacity Tensiometers (HCTs). As such, the novel Northumbria HCT (N-HCT), with an extended suction measuring range (3.5 MPa), was sought after. The N-HCT was employed, in conjunction with other established and proposed direct and indirect suction measurement techniques, to provide the full suction measurement range (saturation to dry conditions). Additionally, a unifying volumetric measurement technique is proposed, based on defining a mathematical model that describes a unique relationship between void ratio and water content, referred to as the Soil Shrinkage and Swelling Curves (SSCs). Having a well-defined SSC, along with the full suction range, allows obtaining complete Soil Water Retention Curves (SWRCs), in drying and wetting paths. SWRCs are a main characterising component of constitutive models for describing the porewater retaining capacity and flow. Obtaining the SWRCs and SSCs provides the relationship between the evolution of the three main variables of the unsaturated soil behaviour: porewater, suction, and void ratio. Additionally, the desaturation and saturation rates were computed. A novel approach is proposed to divide the soil drying into five stages, and the wetting to another four stages. Different yielding points are suggested to mark the transition between the proposed stages, with each holding a coupled hydromechanical significance. While some of the transitional points are conventional, the role of the inflexion point of the SWRC is yet to be established. A strong correlation between the latter and the shrinkage limit is determined and verified for various soils from the literature encompassing different soil types, fabrics, and textures. Finally, the implication on the mechanical constitutive relations and the geotechnical designs is studied. The principal aim of this thesis was to construct a full numerical model that can replicate, to high accuracy, the THM behaviour of soils exposed to free atmospheric conditions. Having such a fully capable model would significantly reduce the uncertainties during the design process of any infrastructure and earthworks project using soils as engineered material (embankments, slopes, landfills). The constitutive equations and their corresponding parameters must be well-defined. The experimental campaign helped caliberate the mechanical component, the SWRCs, and the hydraulic, relative, and thermal conductivities for the soils being simulated. The applied atmospheric conditions on the soil surface are translated into imposed numerical boundary conditions. This entails all relevant atmospheric factors: wind (to transfer coefficients), temperature (heat flux), relative humidity (vapour concentration), rainfall (infiltration rate), and solar radiation (heat flow rate). The developed model successfully captures the THM behaviour and the cracking intensity of the soil exposed to different atmospheric conditions. The simulations were carried out on seven different laboratory specimens in an environmental chamber with controlled atmospheric conditions and one larger-scale field experiment exposed to free atmosphere. Having a developed model capable of simulating soils prepared at a wide variety of different initial conditions and exposed to varying imposed atmospheric conditions can prove to be a valuable feature to predict cracking and shrinkage behaviour for advanced designs of infrastructures using soils as engineering materials. (Español) Esta tesis presenta parte de una investigación en curso sobre el comportamiento termo-hidro-mecánico (THM) y el agrietamiento de suelos no saturados deformables sometidos a ciclos de secado y humectación. Primero se adoptó un enfoque experimental para comprender los principales mecanismos del comportamiento THM de los suelos no saturados. La presión de poros negativa (succión matricial) es una variable principal que caracteriza las diferentes leyes y parámetros constitutivos de los suelos no saturados. Las mediciones directas para rangos de succión altos solo son posibles actualmente utilizando tensiómetros de alta capacidad (HCT). Para ello se han desarrollado los nuevos tensiómetros Northumbria HCT (N-HCT), con un rango extendido (3.5 MPa). Los N-HCT se han empleado con otras técnicas de directas e indirectas ya establecidas o propuestas, para proporcionar el rango completo de la succión (saturación hasta las condiciones secas). Además, se ha propuesto una técnica de medición volumétrica unificadora, basada en la definición de un modelo matemático para las curvas de retracción e hinchamiento del suelo (SSC). Tener una SSC bien definida, junto con las mediciones de rango completo de succión permite obtener las curvas de retención (SWRC), para las trayectorias de secado y mojado. Las SWRC son principales componentes de los modelos constitutivos para describir la capacidad de retención de humedad y las características de flujo. La obtención de las SWRC y las SSC proporciona la relación entre la evolución de las tres variables principales: agua intersticial, succión e índice de poros. Por otra parte, se han calculado también las velocidades de desaturación y saturación. Finalmente, se propone un enfoque novedoso para dividir el secado del suelo en cinco etapas, y el mojado en otras cuatro etapas. Se sugieren diferentes puntos de transición con significado hidromecánico acoplado. Algunos de los puntos son bien conocidos, el papel del punto de inflexión de la SWRC aún no se ha establecido. Se ha verificado una buena correlación entre este último y el límite de retracción para varios suelos a partir de la literatura que abarca diferentes tipos de suelo, estructuras y texturas. Finalmente, se ha estudiado la implicación sobre las relaciones constitutivas mecánicas. El objetivo principal ha sido la obtención de un modelo numérico que pueda replicar, con una alta precisión, el comportamiento THM de los suelos expuestos a condiciones atmosféricas externas. Tener un modelo tan capaz reduciría significativamente las incertidumbres durante el proceso de diseño de proyectos de infraestructura (terraplenes, revestimientos, taludes, vertederos). La campaña experimental implementada proporcionó el componente mecánico, las SWRC y las conductividades hidráulicas y térmicas de las ecuaciones constitutivas y sus parámetros correspondientes para los suelos a simular. Las condiciones atmosféricas aplicadas en la superficie del suelo deben traducirse adecuadamente en condiciones de contorno impuestas, implementando todos los factores relevantes: viento (coeficientes de transferencia), temperatura (flujo de calor), humedad relativa (concentración de vapor), precipitaciones (velocidad de infiltración) y radiación solar (velocidad del flujo de calor). La formulación relevante se obtuvo comparando con las ecuaciones de balance de energía clásicas y con las de la meteorología. El modelo desarrollado reproduce con precisión el comportamiento THM y permite estimar la intensidad de agrietamiento del suelo expuesto a diferentes condiciones atmosféricas para probetas de laboratorio y un ensayo de campo a mayor escala expuesto a condiciones atmosféricas libres. Un modelo capaz de simular suelos preparados con una amplia variedad de condiciones iniciales diferentes, y expuestos a diferentes condiciones atmosféricas es una herramienta valiosa para predecir el comportamiento del agrietamiento y retracción en el proceso de diseños avanzados de infraestructuras.

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Selected Operations Involving Transport of a Single Fluid Phase through a Porous Medium

Cited by 5 publications

References 19 publications

Advances in the Use of Protein-Based Materials: Toward Sustainable Naturally Sourced Absorbent Materials

Advances in the Use of Protein-Based Materials: Toward Sustainable Naturally Sourced Absorbent Materials

Estimating the Permeability of a Porous Ceramic Tile

Experimental and numerical analysis of the unsaturated soil shrinkage and swelling behaviour under different compaction conditions

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