Mesoscale Pores Research Articles

Hierarchical core-shell ZIF-11@ZIF-8 composite nanocatalyst for high-yield simultaneous transesterification-esterifications of sunflower oil to produce biodiesel

Decreasing the mass transfer resistance is a promising technique to prepare an efficient catalyst for improving biomass macromolecules conversion in biodiesel production. In this study, hierarchical core–shell composite nanocatalysts were prepared through a solvothermal technique using zeolitic imidazolate framework-8 (ZIF-8) and ZIF-11 metal–organic frameworks (MOFs). The nanocatalysts were characterized by XRD, FT-IR, BET, FE-SEM, EDS, XPS, TEM, NH3-TPD, and CO2-TPD analyses. The results showed high crystallinity, high surface area (1446.86 m2/g), high pore volume (0.65 cm3 g−1), and mesoscale pore size (2.37 nm). Furthermore, TEM images confirmed the formation of core–shell structure for the composites. The catalytic activity was evaluated in the transesterification of sunflower oil at different operating conditions. The highest biodiesel yield (96.4 %) and full free fatty acid (FFA) conversion were obtained over the ZIF-11@ZIF-8 nanocatalyst at the optimum operating conditions: 120 °C, catalyst concentration of 8 wt%, methanol to oil ratio of 40:1, and 10 h. The ZIF-11@ZIF-8 nanocatalyst showed high thermal and chemical stability after several sequence cycles, leading to high reusability.

Interplay of physical and textural properties in porous, nanostructured hard‑carbons as electrode materials for non-Faradic energy storage devices

This work presents a systematic investigation on the non-Faradic energy storage ability of non-graphitizable, porosity engineered hard‑carbon nanostructures as electrode materials. The persistent challenge of inducing and tuning porosity in hard‑carbon nanostructures is overcome here, by utilizing dendritic fibrous nano silica (DFNS) as a sacrificial template for uniform and conformal deposition of carbon through thermal chemical vapor deposition, leading to the formation of porosity tuned, nanostructured hard‑carbon florets (NCF). This strategy enables precisely crafted six varieties of NCF with varying yet monodisperse dimensions (NCF 90, NCF 350, NCF 366, NCF 430, NCF 540 and NCF 600), SSA (494–719 m2/g) and textural features such as pore volume (0.67–1.24 cm3/g) and pore diameter (3.83–5.65 nm). In contrast to current understanding, NCF 366 with defect length of 16 nm, defect density of 2.65 × 1011 cm−2, micro- to mesoscale pore ratio of 0.16 and specific surface area of 535 m2/g achieves the highest energy density of 14.6 Wh/kg and power density 10.0 kW/kg, when compared to NCF 90 with higher SSA (719 m2/g) and pore volume (1.24 cm3/g). Thus, this work manifests the critical contributions of tuning the pore structures and optimizing the relative contributions from multi-scale pore structures to achieve high-performing energy storage devices.

Growth Kinetics and Porous Structure of Surfactant-Promoted Gas Hydrate.

Surfactants present in tiny amounts in the aqueous phase are known to be efficient gas hydrate promoters; yet, the promotion mechanisms are still not fully understood. Understanding and directing those mechanisms is key to the implementation of gas-hydrate-based applications such as gas storage and separation, secondary refrigeration or water treatment, and desalination. In this work, the growth at the water/gas interface and the porous structure of surfactant-promoted methane hydrate are observed by optical microscopy and Raman imaging in glass capillaries used as optical cells. Hollow crystals are continuously generated and expelled from the methane/water meniscus into the water or surfactant solution, where they ultimately form the skeleton of a porous medium filled with the solution. Unprecedented information is gathered over a range of scales from the molecular scale (crystal structure and cage filling) to the mesoscale (crystal morphologies, growth habits and pore sizes) and macroscale (rates and amounts of water and gas converted into hydrate and hydrate porosity). Following an early steady-state growth regime, a sudden order-of-magnitude increase of the conversion rate occurs, which is related to gaseous methane microbubbles being directly incorporated across the meniscus in the aqueous solution and later converted to methane hydrate. An assessment and comparison are made of the mechanisms and performance of two common anionic surfactants known to be efficient gas hydrate promoters, SDS (sodium dodecyl sulfate) and AOT (dioctylsulfosuccinate sodium or AerosolOcTyl). AOT provides a quicker but more limited conversion into hydrate than SDS, suggesting that it is more appropriate for continuous flow processes while SDS is better suited for gas storage applications. Raman spectra reveal that cage filling by methane of structure I methane hydrate is not affected by surfactants.

3D Printed Microlattices of Transition Metal/Metal Oxides for Highly Stable and Efficient Water Splitting

AbstractDeveloping affordable electrocatalysts is crucial for driving the sustainable energy transition to green hydrogen. Here, a generalizable method known as polymer infusion additive manufacturing is reported for transforming 3D‐printed photopolymers into core–shell micro lattice electrodes for electrocatalytic water splitting with transition metal/metal oxides/carbon heterointerfaces. The optimized free‐standing architectures integrate Cu/CuOx on carbon (Cu/CuOx/C) microlattices, yielding high electrocatalytic activity (overpotential of 145 mV at 10 mA cm−2 and a Tafel slope of 134 mV dec−1) and excellent durability for the hydrogen evolution reaction (HER) (>100 h), surpassing state‐of‐the‐art Cu foams. Additionally, for the oxygen evolution reaction (OER), Co/CoOx on carbon (Co/CoOx/C) microlattices display exceptional activity with the lowest overpotential (1.40 V to gain 10 mA cm−2) among all reported PGM‐free electrodes. The study explores the gas phase mass‐transport properties of these 3D microlattices via microscopic imaging of bubble evolution, finding that the outstanding electrocatalytic performance and long‐term stability of microlattice electrodes leverages their mesoscale (100–300 µm) pores, providing accessibility of electrolytes, maximizing utilization of active sites, and ensuring rapid evolution of gas bubbles. Thus, a simple but pioneering method is introduced for manufacturing 3D mesostructured electrocatalysts with deep control of liquid and gas phase mass‐transport, enhancing the efficacy of alkaline water electrolysis.

Exploring synergistic effects and hydration mechanisms in metakaolin-blended cement system with varying metakaolin and wollastonite content

The quest for sustainable construction practices has led to a growing interest in reducing cement consumption, with supplementary cementitious materials emerging as a promising solution. While reactive admixtures have been extensively studied, there is a noticeable research gap regarding inert admixtures, a critical component of cementitious systems. This paper introduces a novel metakaolin-blended cement system, optimizing the metakaolin, wollastonite, and ground quartz ratios to enhance microstructure and performance. Within this complex quaternary system, we conduct a comprehensive investigation, including assessments of compressive strength, setting times, heat release during hydration, R3 test. Furthermore, we explore hydration products and microstructure through thermogravimetric analysis, X-ray diffraction, backscattered electron imaging, and mercury intrusion porosimetry. The results indicate the influence of wollastonite on clinker reactions and hydration. Although wollastonite slightly increases meso-scale pores, its fibrous shape enhances the overall microstructure. Substituting 50% of metakaolin with wollastonite not only enhances the pozzolanic reactivity but also leads to improved long-term strength. Moreover, the synergistic effect of wollastonite and metakaolin allows for precise tailoring setting times and modulate hydration kinetics, thereby enhancing the overall performance of the cementitious system.

The effect of chemical vapor infiltration process parameters on flexural strength of porous α$\alpha$‐SiC: a numerical model

AbstractThe flexural strength variability of ‐ based ceramics at elevated temperatures creates the need for an Integrated Computational Materials Engineering (ICME) framework that relates the strength of a specimen directly to its manufacturing process. To create this ICME framework, a model must first be developed which establishes a relationship between the chemical vapor infiltration (CVI) process and parameters, the resulting mesoscale pores, and the overall macroscale flexural strength. Here, a nonlinear single‐pore model of CVI is developed used in conjunction with a four‐way coupled thermo‐mechanical damage model. The individual components of the model are tested and a sample system under a four‐point bending test is explored. Results indicate that specimens with an initial porosity greater than 30% require temperatures below 1273 K to maintain structural integrity, while those with initial porosities less than 30% are temperature‐independent, allowing for optimization of the CVI processing time without compromising strength.

In English

Silicas of MCM-41‑type with reactive functional groups are widely used as starting substrates in large variety of post‑synthetic chemical modification pathways. Therefore, variation of their structural characteristics in the process of templated sol‑gel synthesis or post-synthetic treatment is of great importance. The aim of this work was to elucidate the influence of template agent selection on structural features of MCM-41‑type materials with surface silanol and 3‑chloropropyl groups. For this purpose, template-assisted sol-gel condensation of structure forming silanes (tetraethyl orthosilicate and 3‑chloropropyltriethoxysilane) was carried out in the presence of decyltrimethylammonium bromide as structure-directing agent. The capability of cyclic oligosaccharide (β-cyclodextrin) to interact with surfactant micelles in the process of hydrothermal sol-gel synthesis and to influence the formation of mesoporous structure of silica materials was studied. The IR spectroscopy was applied to carry out control under the complete removal of template moieties from pores by extraction procedure and to confirm introduction of 3‑chloropropyl groups into the surface layer of synthesized silicas. Arrangement of mesoscale pores and structural parameters were estimated from the results of X‑ray diffraction and low-temperature adsorption-desorption of nitrogen. It has been found that β‑cyclodextrin as component of hybrid template has positive effect on porous structure of 3-chloropropyl-functionalized MCM-41-type silica causing increase of surface area accompanied with preservation of pore ordering. Moreover, both ionic surfactant and oligosaccharide components of hybrid template act as porogens during sol-gel condensation of structure forming silanes enable to prepare silica materials with micro-mesoporosity. Proposed approach can be useful in synthesis of MCM‑41‑type silicas with surface linker groups and controlled structural characteristics (pore size, geometry and ordering), which have great potential as substrates in design of sophisticated materials.

Optimizing Fast Charging and Wetting in Lithium-Ion Batteries with Optimal Microstructure Patterns Identified by Genetic Algorithm

To sustain the high-rate current required for fast charging electric vehicle batteries, electrodes must exhibit sufficiently high effective ionic diffusion. Additionally, to reduce battery manufacturing costs, wetting time must decrease. Both of these issues can be addressed by structuring the electrodes with mesoscale pore channels. However, their optimal spatial distribution, or patterns, is unknown. Herein, a genetic algorithm has been developed to identify these optimal patterns using a CPU-cheap proxy distance-based model to evaluate the impact of the added pore networks. Both coin-cell and pouch cell form factors have been considered for the wetting analysis, with their respective electrolyte infiltration mode. Regular hexagonal and mud-crack-like patterns, respectively, for fast charging and fast wetting were found to be optimal and have been compared with pre-determined, easier to manufacture, patterns. The model predicts that using cylindrical channels arranged in a regular hexagonal pattern is ∼6.25 times more efficient for fast charging as compared to grooved lines with both structuring strategies being restricted to a 5% electrode total volume loss. The model also shows that only a very limited electrode volume loss (1%–2%) is required to dramatically improve the wetting (5–20 times) compared to an unstructured electrode.

Study on pore structure and permeability sensitivity of tight oil reservoirs

The tight oil reservoir is rich in microscale pores, which has a significant impact on oil and water distribution and seepage. In this paper, first, the microscale pore-throat structure characteristics of tight oil reservoir is analyzed, and the injection medium sensitivity characteristics of the pore-throat structure is explored. Second, considering the dynamic evolution characteristics of permeability, the injection medium influence mode of permeability in tight reservoirs is elucidate. Results show that: (a). The average porosity ratio of microscale pores and small pores (64.35 %) is higher than that of mesoscale pores and large pores (35.65 %), indicating that there are more microscale pores and small pores developed in the reservoir. (b). The mineral content of reservoir rock is 23.93 % quartz, 8.48 % potassium feldspar, 27.28 % plagioclase, 17.63 % calcite, 5.65 % dolomite and 17.03 % clay mineral. (c). Acidic fluids have a weak improvement effect on the porosity of tight sandstone. The average total porosity change rate after interaction with 3 % HF is 8.06 %. (d). Acidic fluids have weak improvement on reservoir pore structure and strong improvement on reservoir permeability. Alkaline fluids have a strong improvement effect on reservoir fluids, but have a moderate to weak improvement effect on reservoir permeability.

The compressive strength and damage mechanisms of pervious concrete based on 2D mesoscale pore characteristics

The compressive performance of pervious concrete depends largely on its pore characteristics. To study the effect of pore characteristics on the compressive strength of pervious concrete, different porosity specimens of pervious concrete were prepared. The Compression test and porosity test was performed on the pervious concrete specimens with a side length of 100 mm. A 2D numerical model of pervious concrete was developed by mesoscale pore characteristics of pervious concrete. The stress distributions and damage modes of pervious concrete during compression were analyzed by conducting uniaxial compressive simulation tests on the established model. The results indicate that the number of pores and maximum pore size of pervious concrete increase as the design porosity increases. The equivalent pore size follows a Gaussian distribution and the characteristic pore size is typically between 1 and 4 mm. The simulation results also indicate that porosity affects the stress distribution of pervious concrete mainly based on the solid phase percentage and contact area. The increase of the number of small pores (when the porosity is certain) is conducive to improving the uniformity of stress transmission, thereby enhancing the compressive strength of pervious concrete.

A Porous Gelatin Methacrylate‐Based Material for 3D Cell‐Laden Constructs

Inside Back Cover: Neuroblastoma cancer cells aggregating inside the mesoscale pores of a bioprinted construct. The combination of tailored porous materials with 3D bioprinting techniques enables to control both the micro and macro architecture of cell-laden constructs. The generation of improved in vitro mimics of in vivo tissues (healthy or diseased) would help precision medicine and the development of patient specific therapeutic approaches. This is reported by Elisa Cimetta and co-workers in article number 2200357.

A Porous Gelatin Methacrylate-Based Material for 3D Cell-Laden Constructs.

3D constructs are fundamental in tissue engineering and cancer modeling, generating a demand for tailored materials creating a suitable cell culture microenvironment and amenable to be bioprinted. Gelatin methacrylate (GelMA) is a well-known functionalized natural polymer with good printability and binding motifs allowing cell adhesion; however, its tight micropores induce encapsulated cells to retain a non-physiological spherical shape. To overcome this problem, blended GelMa is here blended with Pluronic F-127 (PLU) to modify the hydrogel internal porosity by inducing the formation of larger mesoscale pores. The change in porosity also leads to increased swelling and a slight decrease in Young's modulus. All blends form stable hydrogels both when cast in annular molds and bioprinted in complex structures. Embedded cells maintain high viability, and while Neuroblastoma cancer cells typically aggregate inside the mesoscale pores, Mesenchymal Stem Cells stretch in all three dimensions, forming cell-cell and cell-ECM interactions. The results of this work prove that the combination of tailored porous materials with bioprinting techniques enables to control both the micro and macro architecture of cell-laden constructs, a fundamental aspect for the development of clinically relevant in vitro constructs.

Influence of Meso-Scale Pore Structure on Mechanical Behavior of Concrete under Uniaxial Compression Based on Parametric Modeling.

Existing concrete random aggregate modeling methods (CRAMMs) have deficiencies in in the parameterization of the mesoscale pore structure. A novel CRAMM is proposed, whose pore structure is determined by the pore gradation, total porosity, sub-porosity, and pore size of each pore gradation segment. To study the influence of pore structure on the mechanical properties of concrete, 25 mesoscopic concrete specimens with the same aggregate structure but different meso-scale pore structures are constructed and subjected to uniaxial compression tests. For the first time, the influence of sub-porosity of each pore gradation segment, average pore radius (APR), pore specific surface area (PSSA), and total porosity on concrete failure process, compressive strength, peak strain, and elastic modulus were quantitatively and qualitatively analyzed. Results indicate that the pore structure makes the germination and propagation of the damage in cement mortar show obvious locality and affects the formation and expansion of macroscopic cracks. However, it does not accelerate the propagation of the damage in cement mortar from the periphery to the center of the specimen, nor does it change the phenomenon that the ITZ is more damaged than other meso-components of concrete before peak stress. Macroscopic cracks occur in the descending section of the stress–strain curve, and the sudden drops in the descending section of the stress–strain curve are often accompanied by the generation and expansion of macroscopic cracks. The quadratic polynomial, exponential, and power functions can well fit the relationship between total porosity and compressive strength and the relationship between PSSA and compressive strength. The linear, exponential, and power functions can well reflect the relationship between total porosity and compressive modulus and the relationship between compressive modulus and PSSA. For concrete specimens with the same total porosity, the elastic modulus and strength show randomness with the increase in the sub-porosity of macropores and are basically not affected by the APR. Based on the grey relational analysis, the effects of pore structure parameters on the elastic modulus and compressive strength are in the same order: total porosity > T [k1,k2] > T [k2,k3] > T [k3,k4] > T [k4,k5] > AVR > PSSA. The order of influence of the pore structure parameters on the peak strain is: T [k2,k3] > T [k1,k2] > T [k3,k4] > T [k4,k5] > APR > PSSA > total porosity.

Size-Controlled Nanoparticles Embedded in a Mesoporous Architecture Leading to Efficient and Selective Hydrogenolysis of Polyolefins.

A catalytic architecture, comprising a mesoporous silica shell surrounding platinum nanoparticles (NPs) supported on a solid silica sphere (mSiO2/Pt-X/SiO2; X is the mean NP diameter), catalyzes hydrogenolysis of melt-phase polyethylene (PE) into a narrow C23-centered distribution of hydrocarbons in high yield using very low Pt loadings (∼10-5 g Pt/g PE). During catalysis, a polymer chain enters a pore and contacts a Pt NP where the C-C bond cleavage occurs and then the smaller fragment exits the pore. mSiO2/Pt/SiO2 resists sintering or leaching of Pt and provides high yields of liquids; however, many structural and chemical effects on catalysis are not yet resolved. Here, we report the effects of Pt NP size on activity and selectivity in PE hydrogenolysis. Time-dependent conversion and yields and a lumped kinetics model based on the competitive adsorption of long vs short chains reveal that the activity of catalytic material is highest with the smallest NPs, consistent with a structure-sensitive reaction. Remarkably, the three mSiO2/Pt-X/SiO2 catalysts give equivalent selectivity. We propose that mesoscale pores in the catalytic architecture template the C23-centered distribution, whereas the active Pt sites influence the carbon-carbon bond cleavage rate. This conclusion provides a framework for catalyst design by separating the C-C bond cleavage activity at catalytic sites from selectivity for chain lengths of the products influenced by the structure of the catalytic architecture. The increased activity, selectivity, efficiency, and lifetime obtained using this architecture highlight the benefits of localized and confined environments for isolated catalytic particles under condensed-phase reaction conditions.

Mesoscale Pore Structure of Blended Pastes by Water Vapour and N2 Sorption: Sensitivity to Drying and Evaluation of Hydration Degree with Gems

Mesoscale Pore Structure of Blended Pastes by Water Vapour and N2 Sorption: Sensitivity to Drying and Evaluation of Hydration Degree with Gems

Highly-porous Super-Growth carbon nanotube sheet cathode develops high-power Lithium-Air Batteries

Lithium-Air Battery (LAB) is expected to develop ultra-high energy density batteries, but the low rate performance and poor cycle life of present LAB cells hinder practical development. Here we report that a highly porous carbon nanotube (CNT) cathode dramatically enhances the rate capability of LAB. Single-walled CNTs (SWCNTs) with wavy patterns prepared from the Super-Growth (SG) method successfully provided CNT sheets with high porosity of up to 94%. The pore structure was characterized by two distinct pores in size, namely, highly extended mesoscale (approximately 5–200 nm) pores formed inside CNT bundles that provide large surface area for oxygen reduction reaction (ORR) and inter-bundle gaps in a micrometer scale that works for oxygen diffusion path. This porous CNT sheet cathode significantly increased the discharge rate of LAB cells, specifically enabling a high discharge current density of 3.0 mA/cm2 securing practical cell capacity of 3.3 mAh/cm2, which is comparable to the current LiB technology that provides ∼3 mAh/cm2 cell capacity at ∼1C rate (∼3 mA/cm2) discharge. Furthermore, this highly porous cathode was also effective for extending the cycle life of LAB cells. Such bimodal pore architecture of the CNT sheet cathode paves the new strategy for developing high-power energy-dense LAB.

Simulation of Permeation of Saturated Cement Paste Based on a New Meso-scale Pore Network Model

This paper presents the simulation of the permeation of saturated cement paste based on a novel pore network model. First, a 2D hydration model of cement particles was developed by extending the work of Zheng et al. 2005 to provide the background for the network construction. Secondly, the establishment of the pore network model and simulation of permeation of saturated cement paste were carried out. The irregular pores between any two hydrated cement particles were linearized with clear distances as the diameters of pores. The straight tubular pores were interconnected with one another to form the network model. During this process, the weighted Voronoi diagram was employed to operate on the graphical expression of the hydrated cement particles. Water permeation in saturated cement paste was simulated to verify the pore network model. Finally, the factors including water–cement ratio, reaction temperature, reaction time and cement particle size that would influence water permeation were numerically investigated.

Multi-structural evolution of conductive reactive powder concrete manufactured by enhanced ohmic heating curing

This work presented an enhanced ohmic heating (OH) curing method to promote the ultra-high strength of conductive hybrid carbon fibers reinforced RPC (HCF-RPC). This novel curing method was conducted at normal pressure and temperature, but its curing performance was comparable to the autoclave (AC) curing that required strict equipment to provide high pressure and temperature. Hybrid carbon fibers (CFs) and carbon nanofibers (CNFs) were synergistically applied to enhance electric conductivity and heating efficiency of HCF-RPC. Effects of enhanced OH curing on the multi-structural evolution of RPC were clarified and further compared with AC and high temperature stream (HTS) curing. The results showed that enhanced OH curing endowed the curing temperature of ~180 °C to stimulate the compressive strength of HCF-RPC to 104.5 MPa with ultrashort curing duration of 3 h. XRD and TG analyses demonstrated the promoted hydration effect of enhanced OH curing, additional hydration products (tobermorite and xonotlite) were only detected in the enhanced OH and AC cured samples. Furthermore, 29Si NMR data revealed longer average chain length in the enhanced OH cured sample than that of the AC cured sample. Additionally, a refined micro- and meso-scale pore structure was observed in the enhanced OH cured samples from MIP and BET analyses. This work presents enhanced OH curing as an effective method to replace traditional heat treatment methods to rapidly prepare RPC structure.

Ordered Mesoporous Alumina with Tunable Morphologies and Pore Sizes for CO2 Capture and Dye Separation.

We describe a versatile and scalable strategy toward long-range and periodically ordered mesoporous alumina (Al2O3) structures by evaporation-induced self-assembly of a structure-directing ABA triblock copolymer (F127) mixed with aluminum tri-sec-butoxide-derived sol additive. We found that the separate preparation of the alkoxide sol-gel reaction before mixing with the block copolymer enabled access to a relatively unexplored parameter space of copolymer-to-additive composition, acid-to-metal molar ratio, and solvent, yielding ordered mesophases of two-dimensional (2D) lamellar, hexagonal cylinder, and 3D cage-like cubic lattices, as well as multiscale hierarchical ordered structures from spinodal decomposition-induced macro- and mesophase separation. Thermal annealing in air at 900 °C yielded well-ordered mesoporous crystalline γ-Al2O3 structures and hierarchically porous γ-Al2O3 with 3D interconnected macroscale and ordered mesoscale pore networks. The ordered Al2O3 structures exhibited tunable pore sizes in three different length scales, <2 nm (micropore), 2-11 nm (mesopore), and 1-5 μm (macropore), as well as high surface areas and pore volumes of up to 305 m2/g and 0.33 cm3/g, respectively. Moreover, the resultant mesoporous Al2O3 demonstrated enhanced adsorption capacities of carbon dioxide and Congo red dye. Such hierarchically ordered mesoporous Al2O3 are well-suited for green environmental solutions and urban sustainability applications, for example, high-temperature solid adsorbents and catalyst supports for carbon dioxide sequestration, fuel cells, and wastewater separation treatments.

Insights into evaporation from the surface of capillary porous media gained by discrete pore network simulations

Reliable prediction of the drying rate from the surface of a porous medium remains a scientific challenge due to complex interactions between the gas-side boundary layer and porous medium structure. One way to tackle this issue is to opt for a mesoscale pore network model. Two parameter functions (i.e. surface vapor pressure–surface saturation, and the surface vapor transport coefficient–surface vapor concentration relationship) are assessed from the pore network modeling, which can be used in the frame of a continuum model to couple the porous medium with the boundary layer. Moreover, emendation factors are introduced to link the normalized evaporation rate from the wet part of the porous medium surface with the surface wetness or surface saturation. Their evaluation shows that the normalized evaporation rate contributed from wet patches tends to surface saturation with increasing intensity of drying, whereas a similar but weaker trend can be observed with surface wetness. This correlation provides, especially in case of enhanced and non-isothermal drying processes, a simple method for coupling the wet surface region with the gas-side boundary layer in a two-equation continuum model. We have also evaluated the evaporation rate from the wet surface region by inserting pore network modeling data into a modified version of Schlünder's model. The results are not encouraging the derivation of continuum model boundary conditions according to Schlünder, neither for the whole medium surface nor for its wet part.