Water Vapor Migration Research Articles

Breaking the limits of ambient air conditions in evaporative cooling with vacuum-assisted hollow fiber membrane technology

Conventional direct evaporative cooling systems suffer from persistent issues like air–water cross-contamination, mold growth, and scaling of paddings. Moreover, their widespread application in humid climates is hindered by ambient air conditions. This research presents a promising solution in the form of a vacuum-assisted hollow fiber membrane-based evaporative water cooler (VMEWC). It shifts from relying on air state to vacuum pressure for cold water production. A numerical model was established to reflect the coupled heat and mass transfer characteristics, employing Knudsen diffusion to describe water vapor migration within membrane pores. Experimental tests were performed on the constructed VMEWC system, revealing strong alignment between simulation and measured data, with a 2.2 % error in outlet water temperature predictions. Numerical studies explored the effects of six parameters (inlet water temperature, water velocity, shell-side pressure, fiber length, fiber inner diameter, and overall membrane structure parameter) on VMEWC’s outlet water temperature (Tw2), cooling capacity per unit volume (Qv), and coefficient of performance (COP). The results emphasized that elevated inlet water temperature, reduced shell-side pressure, and a large overall membrane structure parameter effectively enhanced the overall performance of VMEWC. Under specific conditions, Qv and COP reached impressive values of 3753.1 kW/m3 and 13.6, respectively. This work provides a novel and practical perspective, offering references for advancing efficient and sustainable refrigeration technologies.

Long‐Term Performance on Drought Mitigation of Soil Slope Through Bio‐Approach of MICP: Evidence and Insight from Both Field and Laboratory Tests

AbstractDrought is a serious global environmental issue that causes water resource scarcity and threatens agriculture and food supplements. This study aims to investigate the long‐term performance of an eco‐friendly technique‐microbial induced carbonate precipitation (MICP) on drought mitigation at field and laboratory scales. Seven in‐situ slopes treated with different MICP rounds and cementation solution concentrations were subjected to 16‐month weathering. Tests were conducted to evaluate the evaporation characteristics, water retention capacity, and CaCO3 distribution. Laboratory soil samples were further prepared to provide evidence related to underlying weathering mechanisms. The results show that MICP has a time‐dependent performance on drought mitigation. After MICP treatment, soil performs a remarkable evaporation suppression ability and the evaporation rate can decrease by 50%. This is attributed to the soluble salts which increase soil water retention capability and dense hard crust which inhibits water vapor migration into the atmosphere. However, the soluble salts and crust are sensitive to weathering thus leading to degradation of MICP. Suffering 16‐month weathering, the MICP‐induced CaCO3 decreases by more than 60%. The evaporation rate of soil increases with MICP rounds and cementation solution concentrations and can reach nearly two times of untreated soil. MICP‐treated field soil exhibits weaker water retention capacity than untreated soil because MICP alters soil microstructure which expands macropores and decreases volume of micropores. Connected macropores act as favorable evaporation channels and accelerate evaporation. To ensure MICP long‐term effects, periodical treatments are necessary. The most effective MICP treatment scheme is four to six treatment rounds and 1.0 M cementation solution.

The roles of different migration mechanisms in the transport of H2O–CH4 gas mixture in shales

Studying the roles of different migration mechanisms in shale matrix gas transport is beneficial for shale gas extraction and CO2 sequestration. The roles of different transport mechanisms in shale H2O–CH4 gas mixture transport were investigated considering their contributions to fluid flux. A permeability model coupling multiple gas migration mechanisms was developed by combining the pore network-related effective medium approximation, which was validated using process data from simultaneous H2O–CH4 transport in shales. The results showed that the gas transport mechanisms dominating methane and water vapor migration in shale differed. Slip flow and Knudsen diffusion contributed approximately 99% to methane migration. Water vapor surface diffusion as well as slip flow and Knudsen diffusion primarily contributed to the water vapor permeability before and after a time point, respectively. Water vapor and methane permeability generally decreased with time. The equilibrium water vapor and methane permeabilities ranged from 2.7699×10−22–12.312×10−22 m2 and 0.2640×10−21–4.9036×10−21 m2, respectively. The methane surface diffusion permeability increased slowly with time before approaching methane monolayer adsorption (before ∼100 s). An increase in relative humidity (approximately 300–3600 s) can promote the transport of water vapor. Water vapor and methane adsorption, especially the condensation of adsorbed water, could largely explain the decrease in shale gas permeability.

Study on the coupling mechanism of water-heat-vapor-salt-mechanics in unsaturated freezing sulfate saline soil

Understanding the internal regularity of unsaturated freezing sulfate saline soil is of utmost importance concerning the durability and stability of cold region engineering in sulfate saline soil areas. One-sided freezing experiments were performed on unsaturated sulfate saline soils with varying salt and moisture contents and temperature gradients to investigate the interplay of water-vapor-salt migration, heat transfer, ice-water and water-vapor phase transformations, salt crystallization, and salt-frost heave. This study presented a novel water-heat-vapor-salt-mechanics coupling model that considers water-vapor-salt migration and its feedback on soil deformation. The results signify that the water accumulation at the top surface of unsaturated freezing sulfate saline soil is primarily due to water vapor migration. Water-vapor-salt migration, ice-water phase transition, and salt crystallization form more ice and salt crystals, filling the air-filled pores and causing significant salt-frost heave. Water vapor transfer and accumulation further exacerbate the soil deformation for unsaturated freezing sulfate saline soil. The calculating results agree with the test data and demonstrate the efficacy of the proposed five-field coupling model. These findings hold significant implications for developing practical solutions for mitigating the negative impacts of salt-frost heave induced by water-vapor-salt transfer in unsaturated freezing sulfate saline soil on construction projects.

Distribution and transformation characteristics of water vapor field in the fissured rock mass and its ecological significance

Opencast mining has produced a large number of high and steep rock slopes, leading to serious safety and environmental challenges. Extreme water scarcity conditions severely impede the survival and development of natural and artificial vegetation when carrying out ecological restoration work. The water vapor field within rocks is a significant but often neglected component of the terrestrial hydrologic cycle and can provide a hidden but critical source of water for plants. However, there is a lack of understanding of the distribution characteristics of the water vapor field within rocks and the pattern of liquid water formation as well as whether it is quantitatively significant and ecologically relevant. This study conducted monitoring experiments on the water vapor field of fissured rock mass and studied the distribution and transformation characteristics of water vapor field in the fissured rock mass and its ecological significance. The results showed temperature and absolute humidity gradually decreased with horizontal depth in spring and summer, and the opposite in autumn and winter. Relative humidity increased rapidly and stabilized with horizontal depth in the spring and summer, and increased rapidly in the autumn and winter, before decreasing slightly. The driving force of water vapor migration is the water vapor partial pressure gradient. In spring and summer, water vapor migrated from air along the fissures to the deep part of the rock mass, while the opposite was true in autumn and winter. While the water vapor migrated through the fissured rock mass, water vapor saturation zones would be produced locally, where potential condensate is generated. The fissure network functioned as a sustained system of water supply pipelines, and the plant roots that grew into the fissures could absorb the condensate, continuously supplying the growth and development of the rock slope plants. This study provides a comprehensive understanding of the rock water vapor field and its effects on ecosystems in arid and semi-arid areas, which can guide the restoration of ecosystems on rock slopes.

Study on coupled heat-water-vapor transfer in buffer material based on SPH method

To study the hydrothermal evolution law in buffer materials, based on the heat balance equation of unsaturated soil and the quality control equation of water migration, a coupled heat-water-vapor model of unsaturated soil is proposed. This model comprehensively considers the transition process of water vapor, the heat transfer caused by water flow and vapor migration, as well as the influence of temperature potential on water flow and vapor migration. The smoothed particle hydrodynamics (SPH) method can be used to calculate their evolution process conveniently. In the solution, the vapor content of heat balance equation is solved first, and then the water content and temperature field are solved, so as the coupling of temperature field between water and vapor field is implemented. The rationality of the model is verified by the tested results of soil column test. According to the established theoretical model, the heat-water-vapor three-field coupling problem of the buffer material in the repository was simulated and studied, and the hydrothermal evolution law inside the buffer material was revealed. On this basis, the influence of the change of groundwater pressure and heat source temperature on the hydrothermal evolution law of buffer material was further analyzed.

Analysis of liquid–vapor mixed migration mechanism in unsaturated soil based on the effect of temperature on soil microstructure

Moisture migration in unsaturated soils is a result of the interaction between temperature and soil microstructure. In order to reveal the mechanism of moisture increase of subgrade soils under diurnal cycle conditions, a series of macro and microscopic tests were carried out on the unsaturated silty clay and sand soil, including liquid–vapor mixed migration tests simulating a one-dimensional subgrade, environmental scanning electron microscope (ESEM), and matrix suction test. Then, the soil microstructure in microscopic images was investigated using the particle (pores) and cracks analysis system (PACS). Next, the relationship between the thermal effects of the soil–water characteristic curve (SWCC) and changes in soil microstructure was analyzed. Finally, the change mechanism of liquid–vapor mixed migration based on the change in soil microstructural under thermal effects was analyzed. The results showed under the diurnal cycle, both the silty clay and sand soil columns appeared in the phenomenon of a “diurnal cycle of water vapor migration”, which led to moisture accumulation at the top of the soil layer. In silty clay soil column, moisture was primarily driven by water vapor pressure and migrated upwards. Additionally, moisture redistribution led to changes in soil microstructure, which in turn influenced the process of moisture migration. The moisture content in the upper soil layer increased making both inter-aggregate and intra-aggregate pores decrease. The moisture content in the lower soil later decreased, leading to the water-holding capacity of the lower soil layer to increase. So, the moisture migration gradually decreased at night. In the sand soil column, moisture migration was mainly driven by gravity potential and migrated downwards. Moisture redistribution made inter-aggregate pore and matrix suction of the upper soil layer increase, leading to an increase in moisture migration at night.

Chitosan-based films blended with moringa leaves and MgO nanoparticles for application in active food packaging

This study aims to address the issue of environmental pollution caused by non-biodegradable petroleum-based food packaging by exploring the application of biodegradable films. Film casting was employed to fabricate food packaging films from chitosan (CS) and polyvinyl alcohol (PVA) polymers blended with moringa extract (MoE) and various concentrations of magnesium oxide nanoparticles (MgO NPs). The films were characterized through multiple techniques, including UV spectroscopy, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), and Fourier-transform Infrared Spectroscopy (FTIR). The study investigated the physicomechanical properties, water solubility, water vapor transmission rate, oxygen permeability, migration test, biodegradability, contact angle, anti-fogging, antibacterial and antifungal activity, and application of the films for food packaging. The results showed that blending CS/PVA films with MoE and MgO NPs significantly improved their mechanical properties. The highest tensile strength of 98 MPa was observed in the CPMMgO-0.5 film. The solubility of the films was low, with CPMMgO-0 and CPMMgO-0.25 demonstrating the lowest solubility as weight decreased by 3.41 % and 3.47 %, respectively. The water vapor transmission rate and oxygen permeability decreased with increasing MgO NP concentrations, with the CPMMgO-0.5 film exhibiting the lowest values. The films also demonstrated good biodegradability, anti-fogging ability, antibacterial and antifungal activity, and low water solubility, enabling bead encapsulation over 14 days in good condition. Moreover, the thermal stability of the films was improved, extending the shelf life of bread. Therefore, the fabricated films provide a promising alternative to non-degradable plastic packaging, which heavily contributes to environmental pollution.

Hollow fiber membrane integrated water cooler: A novel liquid cooling solution

To address the issues of water–air cross-contamination, liquid droplet carryover, and high maintenance costs of traditional water-mediated evaporative cooling systems, the hollow fiber membrane integrated water cooler (MWC) is proposed as a novel liquid cooling solution. The MWC incorporates hydrophobic porous membranes that enable water vapor migration while avoiding direct contact between liquid water and air. In addition, the MWC offers advantages over conventional evaporative cooling paddings in terms of high specific surface area, corrosion resistance, and anti-scaling. To evaluate the cooling performance of a countercurrent MWC, an experimental bench was built to test its outlet water temperature under various operating conditions. The developed numerical model was verified with the measured data. Then, the influence of nine critical parameters, including operating conditions and membrane module specifications, on the outlet water temperature and cooling efficiency of the countercurrent MWC was numerically investigated. The results show that evaporative heat dissipation contributes to more than 80% of the total heat exchange in MWC. Cold and dry ambient air, high inlet water temperature, low water velocity, and high air/water ratio contribute to superior cooling capability. Moreover, the cooling performance of MWC improves with increasing fiber length, inner diameter, packing fraction, and decreasing membrane thickness. In addition, the MWC offers a cooling capacity per unit volume of up to 1094.72 kW/m3, an order of magnitude greater than conventional wet cooling towers. Overall, this work presents theoretical guidelines for optimizing the operating conditions and configuration of countercurrent MWCs.

Cellulose Nanofibers/Pectin/Pomegranate Extract Nanocomposite as Antibacterial and Antioxidant Films and Coating for Paper.

Bio-based polymer composites find increasing research and industrial interest in different areas of our life. In this study, cellulose nanofibers (CNFs) isolated from sugar beet pulp and nanoemulsion prepared from sugar beet pectin and pomegranate extract (PGE) were used for making films and used as coating with antioxidant and antimicrobial activities for paper. For Pectin/PGE nanoemulsion preparation, different ratios of PGE were mixed with pectin using ultrasonic treatment; the antibacterial properties were evaluated to choose the formula with the adequate antibacterial activity. The antioxidant activity of the nanoemulsion with the highest antimicrobial activity was also evaluated. The nanoemulsion with the optimum antibacterial activity was mixed with different ratios of CNFs. Mechanical, greaseproof, antioxidant activity, and antibacterial properties of the CNFs/Pectin/PGE films were evaluated. Finally, the CNFs/Pectin/PGE formulation with the highest antibacterial activity was tested as a coating material for paper. Mechanical, greaseproof, and air porosity properties, as well as water vapor permeability and migration of the coated layer from paper sheets in different media were evaluated. The results showed promising applicability of the CNFs/Pectin/PGE as films and coating material with antibacterial and antioxidant activities, as well as good stability for packaging aqueous, fatty, and acidic food products.

Experimental study on the mechanism of ice layer formation in fractured rock masses in cold regions

The formation and growth of ice layers in fractured rock masses is one of the main causes of frost weathering in bedrock in cold regions. The mechanism of ice layer formation in fractured rock masses was simulated in this study by conducting frost weathering tests on a simulated rock mass with a vertical through fracture, which was fabricated by splicing two cement blocks. The test results were used to propose a novel mechanism for ice layer formation in terms of the initial crack-frost effect in which moisture mainly migrates in vapor form. The continuous accumulation and growth of these frosts eventually forms an ice layer that expands the crack, and the fractured rock simulation model undergoes frost-heaving damage. The frost layer on the rock wall in the negative temperature region is similar to the frosting process on the cold surface of thermodynamic studies. The relative humidity (RH) gradient and temperature gradient were shown to be the factors affecting water vapor migration, where the former plays a direct and dominant role, and the temperature gradient has a very limited direct effect on vapor migration.

Thermal-Moisture Dynamics at Different Underlying Surfaces in Permafrost Regions of the Central Tibetan Plateau by considering the Effect of Rainfall

The Qinghai-Tibetan Plateau (QTP) has undergone an increase in rainfall and a drastic alteration in the moisture-heat regime in active layers and engineering. To investigate the water and heat responses of natural ground and engineering to rainfall, the differences in energy on the ground surface and the thermal-moisture dynamics of different permafrost underlying surfaces were discussed. Based on the meteorological data in 2013 observed at the Beiluhe observation station, three types of underlying surfaces (i.e., natural ground, asphalt pavement, and gravel pavement) were selected to compare the differences in energy balance at the ground surface, water-energy transport process, and coupling mechanism in active layers under rainfall conditions by a coupled water vapor-heat model of the unsaturated frozen soil. The results show that the asphalt pavement greatly increases the surface net radiation and soil surface heat flux, decreases the surface evaporation latent heat, and cuts off the moisture migration between the atmosphere and the active layer. The gravel pavement significantly increases the surface evaporation latent heat to lower the soil surface heat flux, and the amount of moisture in shallow soil is strongly influenced by rainfall and evaporation. Therefore, the moisture migration and accumulation under the asphalt pavement are dominated by the water vapor flux under thermal gradients, whereas the liquid water under the water potential gradients is the major source of moisture migration under the gravel pavement. The heat transfer in the shallow active layer is dominated by heat conduction. The effect of heat conduction, water vapor migration, and phase transition on the soil temperature is evident for the asphalt pavement, while the impact of liquid water migration on the shallow soil temperature for the gravel pavement is significant in the thawing period. As a result, the soil temperature relationship between different underlying surfaces is asphalt pavement>gravel pavement>natural ground. The thickness of the active layer gradually decreases. Although rainfall infiltration promotes the liquid water convection of the gravel pavement, the decrease in heat flux is less than the increase in thermal conductivity. In general, the construction of asphalt pavement and gravel pavement accelerates the degradation of permafrost. The results can provide theoretical and simulated guidance for the stability prediction and analysis of various underlying surfaces in the central QTP where rainfall is increasing.

Heat, water and vapor coupled migration in loess under uniaxial freezing condition

Water vapor migration induces frost damage to airport runways and highways in loess areas. In this study, the freezing point, soil-freezing characteristic curve (SFCC) and soil-water characteristic curve (SWCC) of Xining loess were measured. While the temperature and water profiles of loess columns under three temperature gradients were obtained by uniaxial freezing tests. Results show that the freezing point of loess is positively correlated with water content in the range of 2.6%–34%, which was well fitted by the Boltzmann function. Unfrozen water content declines more pronounced with temperature at higher water contents and power functions were fitted for SFCC. At higher water contents or lower cold-end temperatures, water migration in soil column is more significant. The above functions were introduced to the non-isothermal heat-water-vapor coupled migration model and numerically implemented in COMSOL Multiphysics. It was verified by comparing with uniaxial freezing test data. Under a given temperature gradient, the lower the freezing point, the smaller the frozen depth, the more insignificant the liquid water migration, and the lower volume fraction of ice. Vapor migration is less affected by freezing point but by vapor density and flux.

Study on the frost heave behavior of the freezing unsaturated silty clay

The frost heave behavior of unsaturated soils is related to the water-vapor redistribution, whereas the water-vapor migration processes cannot be directly observed due to the limitations of measurement techniques. To reveal the frost heave behavior of the unsaturated silty clay, five specimens for unsaturated silty clay were prepared. One-side freezing tests for the five specimens were carried out under uniform conditions. The test durations are 12 h, 24 h, 48 h, 96 h, and 192 h, respectively, and the water content profiles in the freezing process were studied by testing final water content profile of each specimen as the profile at that time. The heat-water-vapor migration and frost heave behavior of the freezing unsaturated silty clay were interpreted. The results showed that the temperature variations can be divided into three stages (a sharply cooling stage, a slowly cooling stage, and a steady stage) according to the change rate of temperature, and the duration times of the first and the second stage are short. A mix migration of liquid water and water vapor in unsaturated soils can be experimentally determined during the freezing, and a thin ice forms at the top of the specimens due to the vapor migration and condensation. Meanwhile, the liquid water in unfrozen zone mainly migrates to frozen fringe, and segregated ice forms in the freezing unsaturated soil once enough water accumulates at the frozen fringe. In addition, the frost heave of the specimens is discrete under the uniform test conditions. We selected the relative error and absolute error of the frost heave as evaluation indexes, and further evaluated the repeatability of the test results. Evaluation results showed that the one-side freezing test results are repeatable, and it is an useful testing method to study the heat-water-vapor migration through one-side freezing tests with different test durations under uniform testing conditions. Moreover, the confusion that the frost heave mainly occurred in the top layer of high-speed railway subgrade was explicit solved by the behavior revealed in this paper.

Influence of subgrade filling types on covering effect in seasonally frozen soil area

The existence of a large area of expressway pavement in seasonally frozen soil region causes the moisture in roadbed filler to migrate upward and accumulate under the action of external temperature gradient and road barrier which aggravates the frost heave and thaw settlement of the subgrade. The formation process of subgrade covering effect in seasonally frozen soil area is reproduced by laboratory experiment. The water-vapor-heat model of unsaturated soil is established to simulate the formation process and difference of different subgrade filling cover effect in a certain area of Lanzhou. The results show that under the effect of seasonal temperature changes， soil water accumulates to the bottom of the impervious layer， and the accumulation phenomenon intensifies with freezing-thawing cycles. When the subgrade fillings are sandy soil， silty soil and silty clay， the maximum frozen depths are 1.21， 0.97 and 0.89 m， respectively， due to the difference in thermal conductivity and soil moisture diffusivity of the fillings. Water vapor migration dominates the water transport in shallow ground， which is most significant in silty soil. Water accumulations of sandy soil， silty clay and silty soil subgrade are 0.68%， 2.86% and 12.56%， respectively. The accumulation depth becomes shallower in turn. It is important to prevent and control the subgrade hazards caused by water vapor migration in the existing subgrade engineering. <fig fig-type="abstract-image" id="F1" orientation="portrait" position="float"><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="SP.J.1249-2022-39-1-59/733994E6-A745-493b-B2C8-B61D2BDE06B2-F001.jpg"/></fig>

Adding Kaffir Lime (Citrus hystrix) Leaf Essential Oil to Gelatin Coating for Extending the Shelf Life of Red Snapper Fillet

Red Snappers contain high content protein and water which makes them highly perishable. However, they are widely processed into the fillet. One of the disadvantages of filleting is the short shelf life due to the high water content turning the fillets into an ideal media for bacteria. The edible coating protects the meat from perishability by reducing the water vapor, aroma, and lipid migration. One of the potential protein sources for coating is gelatin. The essential oil content that has a role in inhibiting bacterial growth is citronellal. The present study aimed to determine the effects of adding Kaffir limes (Citrus hystrix) leaf essential oil to a gelatin coating on the shelf life of red snappers’ fillet. An experiment was conducted using a completely randomized design with four treatment groups based on the concentration of Citrus hystrix essential oil and five replications (n = 3 per group). In this regard, the treatments were named P0 (0% of Citrus hystrix), P1 (1% of Citrus hystrix), P2 (1.5% of Citrus hystrix), and P3 (2% of Citrus hystrix). The investigated parameters included total plate count, sensory quality, and acidity. Data analysis was performed using ANOVA followed by Duncan’s multiple range test. The results showed that the addition of 1.5% and 2% Citrus hystrix essential oil decreased the number of bacteria, and led to a higher sensory quality. In conclusion, The addition of Citrus hystrix essential oil in the gelatin-coating process can be used as a method of processing the fishery products to extend the shelf life of red snappers’ fillet at room temperature and inhibit bacterial growth.

A Computational Model of Water Migration in a Closed System of Unsaturated Expansive Clay

Expansive clay behaves like mechanical performances of multi-fissures, and deterioration with the changing moisture. To ensure the safe operation of foundation, the effects of intensive water migration on earth constructions founded on semiarid area, have therefore been received much more attention together with the global warming and climate changes. Herein, analytical models considering respectively liquid water and water vapor migration were presented to address changes in moisture content of unsaturated expansive clay under various water content gradients. Moreover, measured data obtained from migration experiments performed under various water content gradients in a closed system, were utilized to check the validity of analytical equations. Results indicate that the migration of both water vapor and mixed water shows nonlinear relationships with time and location. For the expansive clay with low moisture content, major components of migration water was water vapor, which accounted for 83.61–88.62%; while for the clay with higher water content, the liquid water was dominant migration of water due to more free water around the soil particles. The proposed model is helpful to investigate moisture migration law in the unsaturated expansive clay.

Use of basil leaf ethanol extract in alginate base edible film

Alginate is usually obtained by extracting from brown seaweed, mainly Sargassum sp which grows almost along the coasts of the islands in Indonesia. One of the efforts to utilize alginate was by employing as raw material in the production of edible film. The disadvantage of films made from carbohydrates is that they are not very good at regulating water vapor migration. One way to improve performance of edible film in inhibiting water vapor transmission is to add vegetable oil. In this study, the effect of adding basil leaf ethanol extract was observed to improve the performance of alginate-based edible film. Basil leaf extract was added at concentrations of 0.5%, 1% and 1.5%. The resulting edible films were observed for chemical characteristics (moisture content), physical characteristics (thickness, tensile strength, water vapor transmission rate, elongation, brightness, solubility) and antibacterial performance. The results showed that the concentration of basil leaf extract had a significant effect on moisture content, thickness, tensile strength, water vapor transmission rate (WVTR), and elongation values. Edible films do not have antibacterial activity against Staphylococcus aureus and Escherichia coli. The addition of basil leaf extract at a higher concentration resulted in an alginate-based edible film with lower moisture content, higher water solubility, higher thickness, higher tensile strength, lower WVTR, and lower elongation percentage.

Influence of amorphous metallic fibers on spalling properties of high-strength concrete exposed to high temperature

This study examined the effect of amorphous metallic (AM) fibers on the spalling properties of high-strength concrete. Nine specimens with concrete strengths of 100 MPa and 120 MPa were evaluated with mix proportions of polypropylene (PP) fibers of 0.15% and 0.25% by concrete volume, and proportions of AM fibers of 0.3% and 0.5% by concrete volume. These specimens were then heated in accordance with the ISO-834 heating curve. The movement of water vapor through a pore network formed by molten PP fibers was found to be a dominant factor controlling the spalling of high-strength concrete. Spalling control was not found to be significantly affected by the addition of 0.3% AM fibers; however, when 0.5% AM fibers was added, cracking was limited and so were paths for water vapor migration, increasing the likelihood of a moisture clog and creating the differential internal pressure often blamed for concrete spalling.

Isothermal diffusion of water vapor in unsaturated soils based on Fick’s second law

In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.