Diffusion Coefficient Of Water Research Articles

Kinetics model of crystal nucleation and growth in supercooled water for designing ice-templating soft matter scaffold

Ice-templating technology has recently attracted extensive attention to achieve programed structure-property relationships in porous soft matter scaffolds. However, there is a huge gap existed between theoretical understanding and practical applications of nucleation kinetics and growth of ice crystals in supercooled water. This paper establishes a nucleation kinetics model of crystal growth in supercooled water, for designing ice-templating soft matter scaffolds with programmable structure-property relationship. A phase transition model was firstly formulated to characterize liquid-liquid phase transition of supercooled water, based on a two-state model and free-volume theory. Effects of diffusion coefficient and density of the supercooled water on ice nucleation kinetics and crystal growth were investigated, based on the classic nucleation theory. Analytical results showed excellent agreement with experimental data, with correlation indices of R2=90.7 % for diffusion coefficients and R2=94.0 % for densities, respectively. The model predicted a nucleation rate of 31.7 m−3∙s−1 at 200 K and peak nucleation rate and crystal growth rates appearing at 183 K and 227 K. Constitutive relationships among mechanical behaviors, ice nucleus radius, nucleation ratio, and crystallization growth rate, were developed for the ice-templating scaffolds, based on the affine model theory and verified with finite element analysis results (R2= 99.9 %) and experimental results (R2 = 95.8 %). Finally, the prediction results using the proposed model were further verified using the experimental data reported in the literature. This study provides a new methodology to describe the nucleation kinetics and growth of ice crystals in supercooled water and programmable structure-property relationships in ice-templating soft matter scaffolds.

Changes of Temperature and Moisture Distribution over Time by Thermo-Hydro-Chemical (T-H-C)-Coupled Analysis in Buffer Material Focusing on Montmorillonite Content

Bentonite is used as a buffer material in engineered barriers for the geological disposal of high-level radioactive waste. The buffer material will be made of bentonite, a natural clay, mixed with silica sand. The buffer material is affected by decay heat from high-level radioactive waste, infiltration of groundwater, and swelling of the buffer material. The analysis of these factors requires coupled analysis of heat transfer, moisture transfer, and groundwater chemistry. The purpose of this study is to develop a model to evaluate bentonite types and silica sand content in a unified manner for thermo-hydro-chemical (T-H-C)-coupled analysis in buffer materials. We focused on the content of the clay mineral montmorillonite, which is the main component of bentonite, and developed a model to derive the moisture diffusion coefficient of liquid water and water vapor based on Philip and de Vries, and Kozeny–Carman. The evolutions of the temperature and moisture distribution in the buffer material were analyzed, and the validity of each distribution was confirmed by comparison with the measured data obtained from an in situ experiment at 350 m in depth at the Horonobe Underground Research Center, Hokkaido, Japan.

Measurement of the rotational relaxation time of intracellular water in dried yeast and Jurkat cells by near infrared spectroscopy

Molecular mobility of intracellular water is a crucial parameter in the study of the mechanism of desiccation tolerance. As one of the parameters that reflecting molecular mobility, the viscosity of intracellular water has been found intimately related with the protection of the phospholipid membrane because it quantifies the diffusion ability of water and mass in the intracellular environment. In this work we measured the intracellular water relaxation time, which can be translated into water viscosity, by using a previously established NIR-dielectric method to monitor the drying process of baker's yeast and Jurkat cells with different desiccation tolerance. We found that intracellular saccharide can significantly decrease the intracellular water viscosity. Also, the intracellular water diffusion coefficient obtained from this method were found in good agreement with other reports.

Intrinsic Water Transport in Moisture-Capturing Hydrogels.

Moisture-capturing hydrogels have emerged as attractive sorbent materials capable of converting ambient humidity into liquid water. Recent works have demonstrated exceptional water capture capabilities of hydrogels while simultaneously exploring different strategies to accelerate water capture and release. However, on the material level, an understanding of the intrinsic transport properties of moisture-capturing hydrogels is currently missing, which hinders their rational design. In this work, we combine absorption and desorption experiments of macroscopic hydrogel samples in pure vapor with models of water diffusion in the hydrogels to demonstrate the first measurements of the intrinsic water diffusion coefficient in hydrogel-salt composites. Based on these insights, we pattern hydrogels with micropores to significantly decrease the required absorption and desorption times by 19% and 72%, respectively, while reducing the total water capacity of the hydrogel by only 4%. Thereby, we provide an effective strategy toward hydrogel material optimization, with a particular significance in pure-vapor environments.

Mechanism and Kinetics of Water Absorption of Plantain Fibre Reinforced Bio-Composites

Mechanical characteristics, dimensional stability, and bonding strength are all impacted by water sorption in polymer filler materials. The diffusion coefficient (D) of water through polymer composite, should be determined to understand the impact of the deterioration on service life and micro-leakage. In this study, the kinetics and properties of water absorption by short-term immersion in room-temperature plantain fibre reinforced epoxy bio-composites (PFRC), were studied. 5, 10, 20, and 30 percent, plantain fiber (PF) volume fractions of bio-composite specimens were made. Due to the high cellulose content of natural fibers (NF), the percentage of moisture absorption grew as the PF volume fraction increased. The mechanism and kinetics of PFRC's water absorption were found to follow the Fickian diffusion mode and had the propensity to behave in the Fickian mode.

Dynamic modeling of the occurrence, sources, and environmental behavior of polybrominated diphenyl ethers in Zhelin Bay, China

This study analyzed polybrominated diphenyl ethers (PBDEs) in Zhelin Bay, China, investigating their occurrence, sources, and environmental behavior. PBDE congeners were detected in all sampled media. The Σ13PBDE concentrations in the dissolved phase ranged from 1.04 to 41.40 ng/L, while the concentrations ranged in suspended particulate matter from 0.02 to 12.56 ng/L. In sediments, PBDE concentrations ranged from 1.41 to 8.57 ng/g. The higher proportion of PBDEs in the dissolved phase in the bay than in the estuary is attributable to the type of PBDE products used in the aquacultural process in Zhelin Bay. Moreover, correlation analysis between PBDE concentrations and environmental parameters showed that the primary factor influencing PBDE concentrations in Zhelin Bay sediments may shift from riverine inputs to aquaculture. Principal component analysis and positive matrix factorization revealed that PBDEs in the water of Zhelin Bay primarily originated from the degradation of octa-BDE, deca-BDE, and penta-BDE products employed in aquaculture. In contrast, the PBDEs in Zhelin Bay sediments mainly originated from riverine inputs. In addition, a level IV dynamic fugacity-based multimedia model was used to simulate the temporal variation of PBDE concentrations in Zhelin Bay. Modeled short-term trends showed a relatively swift transport of PBDE congeners in the water column to the atmosphere and sediments. Over the long term, sediment concentrations gradually decreased, in contrast to the less rapid declines observed in the atmosphere and water. Furthermore, this study revealed that the transport and transformation processes of PBDEs in the Zhelin Bay environment were considerably influenced by the diffusion coefficient in water, the water-side mass transfer coefficient at the water–sediment interface, the sediment resuspension rate, and the organic carbon–water partition coefficient.

Impact of water absorption on the creep performance of epoxy/microcrystalline cellulose composites

AbstractRecently, considerable effort has been made to study cellulose/epoxy composites. However, there is a gap when it comes to understanding the post‐conditioning anomalous effect of moisture uptake on their mechanical and dynamic‐mechanical properties, and on their creep behavior. In this work, up to 10.0 wt% microcrystalline cellulose (MCC) was incorporated into epoxy resin by simple mixing and sonication. Epoxy/MCC composites were fabricated by casting in rubber silicone molds, and rectangular and dog‐bone test specimens were produced. The moisture uptake, dynamic mechanical, chemical, tensile, and creep behavior were evaluated. The incorporation of MCC increased the water diffusion coefficient. The changes in storage modulus and glass transition temperature, combined with Fourier‐transform infrared spectroscopy analysis, evidenced that water sorption in epoxies causes both plasticization and additional resin crosslinking, although the latter is prevented by the addition of MCC. The creep strain of the composites increased by 60% after conditioning, indicating that plasticization induced by water sorption plays an important role in the long‐term properties of the composites.

Quality and Process Optimization of Infrared Combined Hot Air Drying of Yam Slices Based on BP Neural Network and Gray Wolf Algorithm

In this paper, the effects on drying time (Y1), the color difference (Y2), unit energy consumption (Y3), polysaccharide content (Y4), rehydration ratio (Y5), and allantoin content (Y6) of yam slices were investigated under different drying temperatures (50–70 °C), slice thicknesses (2–10 mm), and radiation distances (80–160 mm). The optimal drying conditions were determined by applying the BP neural network wolf algorithm (GWO) model based on response surface methodology (RMS). All the above indices were significantly affected by drying conditions (p < 0.05). The drying rate and effective water diffusion coefficient of yam slices accelerated with increasing temperature and decreasing slice thickness and radiation distance. The selection of lower temperature and slice thickness helped reduce the energy consumption and color difference. The polysaccharide content increased and then decreased with drying temperature, slice thickness, and radiation distance, and it was highest at 60 °C, 6 mm, and 120 mm. At 60 °C, lower slice thickness and radiation distance favored the retention of allantoin content. Under the given constraints (minimization of drying time, unit energy consumption, color difference, and maximization of rehydration ratio, polysaccharide content, and allantoin content), BP-GWO was found to have higher coefficients of determination (R2 = 0.9919 to 0.9983) and lower RMSEs (reduced by 61.34% to 80.03%) than RMS. Multi-objective optimization of BP-GWO was carried out to obtain the optimal drying conditions, as follows: temperature 63.57 °C, slice thickness 4.27 mm, radiation distance 91.39 mm, corresponding to the optimal indices, as follows: Y1 = 133.71 min, Y2 = 7.26, Y3 = 8.54 kJ·h·kg−1, Y4 = 20.73 mg/g, Y5 = 2.84 kg/kg, and Y6 = 3.69 μg/g. In the experimental verification of the prediction results, the relative error between the actual and predicted values was less than 5%, proving the model’s reliability for other materials in the drying technology process research to provide a reference.

Characterization of Water Absorption, Thickness Swelling and Diffusion Coefficient of Natural Fiber/Epoxy Bio-Composites for Applications in Aquatic Environment

The aim of this work was to study the suitability of wood flour, fluted pumpkin stem and rice husk flour/epoxy bio-composites for application in aquatic environment. The water absorption, thickness swelling and diffusion coefficient of wood flour, fluted pumpkin stem flour, rice husk flour/epoxy bio-composites were investigated. Composites were prepared by the hand layup method at varying weight percentages of filler reinforcement (10, 20 & 30%). The increase in the addition of the fillers enhanced the water absorption, thickness swelling and diffusion coefficient of the composites. However, after 14 days of immersion, all the composites attained an equilibrium state. It was observed that with 30wt% filler loading, the fluted pumpkin stem flour epoxy composites showed the highest water absorption of 40.5%, diffusion coefficient of 10.80x10-8m2/s, followed by the wood flour epoxy composite with water absorption of 35.3%, diffusion coefficient of 8.17x10-8m2/s, while rice husk flour epoxy composites had the lowest water absorption of 16.5%, diffusion coefficient of 6.12x10-8m2/s. The same trend was observed for the composites with 20 and 10 wt% filler loading. In terms of thickness swelling, the wood flour composite showed 1.62%, followed by fluted pumpkin stem flour composite 1.40% and rice husk flour composite 0.35% with 30wt% filler loading. A similar trend was observed for the composites with 20 and 10wt% filler loading. This study can be useful to comprehend the effect of water absorption on the performance of natural fiber composites and help in creating designer compositions for use in building, construction and automotive.

Dynamics of an aqueous suspension of short hyaluronic acid chains near a DPPC bilayer.

The synergy between hyaluronic acid (HA) and lipid molecules plays a crucial role in synovial fluids, cell coatings, etc. Diseased cells in cancer and arthritis show changes in HA concentration and chain size, impacting the viscoelastic and mechanical properties of the cells. Although the solution behavior of HA is known in experiments, a molecular-level understanding of the role of HA in the dynamics at the interface of HA-water and the cellular boundary is lacking. Here, we perform atomistic molecular dynamics simulation of short HA chains in an explicit water solvent in the presence of a DPPC bilayer, relevant in pathological cases. We identify a stable interface between HA-water and the bilayer where the water molecules are in contact with the bilayer and the HA chains are located away without any direct contact. Both translation and rotation of the interfacial waters in contact with the lipid bilayer and translation of the HA chains exhibit subdiffusive behavior. The diffusive behavior sets in slightly away from the bilayer, where the diffusion coefficients of water and HA decrease monotonically with increase in HA concentration. On the contrary, the dependence on HA chain size is only marginal due to enhanced chain flexibility as their size increases.

Pore‐Scale Modeling of Water and Ion Diffusion in Partially Saturated Clays

AbstractAn accurate mechanistic understanding of solute diffusion in partially saturated clays is critical for assessing the safety of deep geological repositories for radioactive waste. In this study, a pore‐scale numerical framework is developed to simulate water and ion diffusion in partially saturated clays. First, the two‐phase Shan‐Chen Lattice Boltzmann method is employed to establish the liquid‐gas distribution in a reconstructed three‐dimensional pore geometry of a clay. An equivalent solute method is also developed and validated to improve the numerical stability of the solution at the liquid/gas interface corresponding to steep variations of the concentration and diffusion coefficient of the water tracer. By using a mobility‐distance relationship from molecular simulations, Fick's law is numerically solved to simulate water diffusion in nanopores, while the coupled Poisson‐Boltzmann‐Nernst‐Planck equations are solved to simulate ion diffusion under the influence of the electrical double layer (EDL). Our model reveals that the decrease of relative effective diffusion coefficients during the desaturation is more pronounced for ions than for water, due to the additional transport pathway of water tracers in the gas phase. The obtained effective diffusion coefficients of tritiated water and ions agree well with reported data from compacted sedimentary rocks. By comparing the local electric potential and the distribution of ion concentrations in single pores, the simulation results suggest that the EDL in unsaturated clays has a more complex influence on ion distribution than under fully water‐saturated conditions. This study provides critical insights into the coupled transport processes of solutes in partially saturated clays.

ReaxFF molecular dynamics of graphene oxide/NaCl aqueous solution interfaces.

In this work, the interaction of NaCl aqueous solution with graphene (G), graphene oxide (GO), and graphite oxide (GTO) is studied using the ReaxFF module of Amsterdam Modeling Suite (AMS) software. We consider four models using the NaCl aqueous solution, containing a graphene sheet (G), a single sheet of GO with epoxide and hydroxyl groups on its surface, 4 layers of GO to model GTO, and a bulk NaCl solution as a reference. The structural and dynamical properties of G, GO, and GTO were quantified by analyzing the functional groups, radial distribution functions, density profiles and diffusivities of water and ions. Due to the reactive force field, the systems underwent spontaneous modification of surface functional groups during the first 750 ps after which the structure stabilizes (the energy stabilizes in less than 400 ps). Pristine graphene in contact with the NaCl solution formed hydroxyl groups on the edges, i.e., converted to partially reduced graphene oxide. The epoxy groups (Oe) on the initial GO were rather unstable, leading to a reduction of their number, however, there was an increase in the number of hydroxyl groups (Oh), mainly at the edges. The interactions of NaCl with the carbon-based sheets are rather weak, including GO and GTO which are decorated with numerous functional groups. Diffusion coefficients of water agree with the available data, but discrepancies in Na+ and Cl- diffusivity compared to other references underscore the need for further development in the dynamic parameters of the reactive force field used. In essence, our research provides specific data previously unreported, laying a foundation for advancing water desalination system design. The study's novelty lies in its realistic approach to graphene/graphene oxide modification, comprehensive characterization, and the application of the reactive force field to explore the graphene oxide-NaCl aqueous interface, contributing to the development of a practical membrane system for water desalination.

Electric-field-induced structure and dynamics of an ethanol-water mixture in hydrophobic-hydrophilic nanochannels.

Understanding the behavior of confined fluid mixtures under external electric fields is essential for advancing scientific knowledge and improving a wide range of technological applications, from energy systems to biological processes. An electric field has been widely used to investigate the phase transition of water and modification of interfacial water at the nanoscale. However, the structure and dynamics of the interfacial layer in complex confined fluid mixtures, such as ethanol-water mixtures, remain unexplored under the influence of an electric field. In this study, we explore the structural and dynamic behavior of binary ethanol-water mixtures confined within slit-like hydrophilic (mica) and hydrophobic (graphene) nanochannels under an external electric field using classical molecular dynamics (MD) simulations. We find two distinct interfacial water layers near the hydrophilic mica surface, and a more pronounced sharp peak appears near the hydrophobic graphene sheet with increasing electric field. The density maxima of the -OH and -CH3 groups of ethanol shift towards and away from the graphene surface with an increasing electric field. Our simulations reveal that the electric field strongly impacts the inter and intralayer hydrogen bonding among water and ethanol molecules. The diffusion coefficient of water slightly increases with the electric field and then reduces with an electric field for a lower concentration of ethanol. This finding reveals that the electric field influences the desorption of interfacial water near the hydrophilic mica surface, which can be an implication for diverse technological applications like modifying surface wettability.

The Utility of Apparent Water Diffusion Coefficient Maps for Evaluating the Presence of Myometrial Invasion in Patients with Endometrial Cancer.

To assess the utility of apparent diffusion coefficient maps (ADC) for diagnosing myometrial invasion (MI) in endometrial cancer (EC). This retrospective study included 164 patients (mean age, 56 years; range, 25-89 years) who underwent preoperative MRI for EC with <1/2 MI or no MI between April 2016 and July 2023. Five sequences were evaluated: T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), ADC, dynamic contrast-enhanced T1-weighted imaging (DCE-T1WI), and contrast-enhanced T1WI (CE-T1WI). Three experienced radiologists independently assessed the sequences for MI. For ADC, MI was determined if the endometrial-myometrial junction-tumor boundary had disappeared. Additionally, the assessment of MI was performed using the combination of T2WI, DWI, and ADC, as well as T2WI, DCE-T1WI, and CE-T1WI. The sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve (AUC) for the presence of MI were calculated and compared between the sequences and combinations. Inter-reader agreement was assessed using kappa (κ) statistics. The sensitivity of ADC was significantly higher than T2WI (P < 0.001) and DCE-T1WI (P = 0.018) for one reader and significantly higher than CE-T1WI (P = 0.045 and 0.043) for two readers. The specificity of ADC was significantly lower than T2WI (P = 0.015 and < 0.001) and CE-T1WI (P = 0.031 and 0.01) for two readers and significantly lower than DCE-T1WI (P = 0.031) for one reader. The AUC of ADC was significantly higher than T2WI (P = 0.048) and DCE-T1WI (P = 0.049) for one reader. The combination including ADC showed higher positive predictive value for all three readers compared to any sequence or combination including contrast enhancement. Additionally, ADC demonstrated the highest agreement rates. ADC had high sensitivity for MI and the highest agreement rate among all sequences. Thus, this sequence, combined with other sequences, can be crucial for a comprehensive evaluation of MI.

Thin‐Layer Drying Model, Drying Rate, and Effective Water Diffusion Coefficient of Pelleted Feed

In this study, classic thin‐layer drying models such as the Page model, Verma model, and Two‐term model were used to fit the thin‐layer drying data of feed. Based on this, a novel thin‐layer drying model for pelleted feed (modified Verma model) was proposed. The results indicate that the new model is the optimal choice for describing the drying kinetics of pelleted feed for growing pig and calf. The drying rate of pelleted feed is linearly correlated with the feed moisture content. The effective water diffusion coefficient for pelleted feed of growing pig and calf ranges from 1.86 × 10−10 to 2.75 × 10−9 m2/s and 3.32 × 10−10 to 3.87 × 10−9 m2/s, respectively. The activation energy (Ea) for moisture diffusion in both types of feed is 26.42 kJ/mol and 25.86 kJ/mol, respectively. By establishing predictive models for model parameters based on air temperature and air velocity variables, the new model demonstrates extrapolation capability, wide applicability, and practical value. This work lays the foundation for developing a similarly characterized deep‐bed cooling drying model for pelleted feed.

Finely tuned water structure and transport in functionalized carbon nanotube membranes during desalination.

Molecular dynamics simulations were performed to tune the transport of water molecules in nanostructured membrane in a desalination process. Four armchair-type (7,7), (8,8), (9,9) and (10,10) carbon nanotubes (CNTs) with pore diameters around 1 nm were chosen, their interior surfaces were modified with -OH, -CH3 and -F groups. Simulation results show that water transport in nanochannel depends on confined water structures which could be regulated by precisely controlled channel diameter and chemical functionalization. Increasing CNT diameter changes water structures from single-file-like to be square and hexagonal-like, then into a disordered pattern, resulting in a concave-shaped trend of water permeance. The -OH functional groups promote structural ordering of water molecules in (7,7) CNT, but disrupt water structures in (8,8) and (9,9) CNTs, and reduce the order degree of water molecules in (10,10) CNT, moreover, exert an attraction to enhance surface friction inside channel. The -CH3 groups induce more strictly single-file movement of water molecules in (7,7) CNT, turning water structures in (8,8) and (9,9) CNTs into two and triangular column arrangements, improving water transport, however, causing again square-like water structure in (10,10) CNT. Fluorinations of CNT make water structure more disordered in (7,7), (9,9) and (10,10) CNTs, while enhance the square water structure in (8,8) CNT with a lower water permeance. Through changing channel diameter and functionalization, the low tetrahedral order corresponds to a more single-file-like water structure, associated with rapid water diffusion and high permeability; an increase in tetrahedrality results in more ice-like water structures, lower water diffusion coefficients, and permeability. The results of this study demonstrate that water transport could be finely regulated via a functionalized CNT membrane.

Assessment of calcium alginate gels as wall materials for encapsulation systems.

Calcium alginate gels are widely used to encapsulate active compounds. Some characteristic parameters of these gels are necessary to describe the release of active compounds through mechanistic mathematical models. In this work, transport and kinetics properties of calcium alginate gels were determined through simple experimental techniques. The weight-average molecular weight ( = 192 × 103 Da) and the fraction of residues of α-l-guluronic acid ( = 0.356) of sodium alginate were determined by capillary viscometry and 1 H-nuclear magnetic resonance at 25 °C, respectively. Considering the half egg-box model, both values were used to estimate the molecular weight of calcium alginate as = 2.02 × 105 Da. An effective diffusion coefficient of water ( = 2.256 × 10-9 m2 s-1 ) in calcium alginate was determined using a diffusion cell at 37 °C. Finally, a kinetics constant of depolymerization ( = 9.72 × 10-9 m3 mol-1 s-1 ) of calcium alginate was obtained considering dissolution of calcium to a medium under intestinal conditions. The experimental techniques used are simple and easily reproducible. The obtained values may be useful in the design, production, and optimization of the alginate-based delivery systems that require specific release kinetics of the encapsulated active compounds. © 2023 Society of Chemical Industry.

Water Effective Diffusion Coefficient in Dairy Powder Calculated by Digital Image Processing and through Machine Learning Algorithms of CLSM Micrographs.

Rehydration of dairy powders is a complex and essential process. A relatively new quantitative mechanism for monitoring powders' rehydration process uses the effective diffusion coefficient. This research focused on modifying a previously used labor-intensive method that will be able to automatically measure the real-time water diffusion coefficient in dairy powders based on confocal microscopy techniques. Furthermore, morphological characteristics and local hydration of individual particles were identified using an imaging analysis procedure written in Matlab©-R2023b and image analysis through machine learning algorithms written in Python™-3.11. The first model includes segmentation into binary images and labeling particles during water diffusion. The second model includes the expansion of data set selection, neural network training and particle markup. For both models, the effective diffusion follows Fick's second law for spherical geometry. The effective diffusion coefficient on each particle was computed from the dye intensity during the rehydration process. The results showed that effective diffusion coefficients for water increased linearly with increasing powder particle size and are in agreement with previously used methods. In summary, the models provide two independent machine measurements of effective diffusion coefficient based on the same set of micrographs and may be useful in a wide variety of high-protein powders.

Simulation study on the coupled heat and mass transfer of CO2 in a heavy oil-water liquid system based on an improved lattice Boltzmann (LB) method

This study investigates the heat and mass transfer when low-temperature CO2 diffuses in a heavy oil–water liquid system based on an improved Lattice Boltzmann (LB) method. First, we determine the CO2 diffusion coefficients in heavy oil and water and the heat transfer coefficients of heavy oil and water using the pressure drop (DP) method and the laser flash (LF) method, respectively. Then, a numerical model that couples the heat and mass transfer in the system is established based on the improved LB method. The effect of low-temperature CO2 on the temperature field of the system and the effect of changes in the temperature field on CO2 diffusion are investigated. Finally, we develop a micro-model reproducing the heat and mass transfer of CO2 in water and heavy oil-saturated porous media to validate the accuracy of the numerical model. The results demonstrate that the CO2 diffusion coefficients in heavy oil and water linearly increase with the temperature increases. The heat transfer coefficients of heavy oil and water are insensitive to the changes in temperature. The heat transfer process has a great impact on the mass transfer of CO2 in the liquid system. The CO2 diffusion velocity slows down as the system temperature decreases because of the heat transfer (from 400 K to 300 K), leading to a reduction percentage of 300 % in the CO2 front movement velocity. Compared to the scenarios neglecting heat transfer, CO2 diffusion distance and amount decrease by 38 % and 50 %, respectively because of the changes in the temperature field of the system.

Hydrothermal aging of glass fiber epoxy‐carbon nanocomposites and its service life predictions based on tensile strength

AbstractThis paper investigates the hydrothermal aging of pultruded glass‐fiber reinforced epoxy nanocomposite rods with carbon nanofillers. The nanocomposites developed in this study are proposed for the core of high‐tension low‐sag conductors in power transmission. Nanocomposites were fabricated with a nanomodified matrix containing 0.2 wt.% of multi‐walled carbon nanotubes and 0.6 wt.% of graphene nanoplatelets. The epoxy nanocomposites tensile strength and life predictions were determined under different water aging conditions. Objective of the study is to evaluate the water absorption kinetics and its impact on tensile strength, microstructure and to compute the service life under hydrothermal aging by predictive techniques. Nanocomposites were aged in water at 30, 50, and 80°C for a duration of 3000 h, and the microstructure and chemical composition were investigated. Based on Arrhenius's theory, a service life prediction model based on the tensile‐strength of the nanocomposite is established for hydrothermal aging. The results have shown that the addition of carbon nanofillers to the epoxy matrix improves the hydrophobicity and reduces the water diffusion coefficient. Water absorptions of the nanocomposites are observed to follow Fick's law, and its influence on the mechanical properties of the nanocomposite is evident and is more significant in epoxy composites without carbon nanofillers. After 3000 h of immersion at 50 and 80°C, the tensile strength retention is above 85%. The hydrothermal environment accelerates the development of micro‐voids and cracks, which are initially formed and observed to be the primary reason for the degradation in mechanical strength under service conditions, in addition to debonding of the fibers.Highlights Carbon nanocomposites were aged at different temperatures and durations. Service life prediction model established based on Arrhenius's theory. Addition of carbon nanofillers enhances hydrophobicity and reduces water diffusion. Tensile strength retention above 85% after 3000 h of aging. Hydrothermal aging accelerates aging contributing to strength degradation.