Moisture Transfer Research Articles

Fractional-Order Modeling of Heat and Moisture Transfer in Anisotropic Materials Using a Physics-Informed Neural Network.

Mathematical models of heat and moisture transfer for anisotropic materials, based on the use of the fractional calculus of integro-differentiation, are considered because such two-factor fractal models have not been proposed in the literature so far. The numerical implementation of mathematical models for determining changes in heat exchange and moisture exchange is based on the adaptation of the fractal neural network method, grounded in the physics of processes. A fractal physics-informed neural network architecture with a decoupled structure is proposed, based on loss functions informed by the physical process under study. Fractional differential formulas are applied to the expressions of non-integer operators, and finite difference schemes are developed for all components of the loss functions. A step-by-step method for network training is proposed. An algorithm for the implementation of the fractal physics-informed neural network is developed. The efficiency of the new method is substantiated by comparing the obtained numerical results with numerical approximation by finite differences and experimental data for particular cases.

Predictability of extreme southwest monsoon rainfall over Myanmar by using a physics-based empirical modeling approach

The study examines the ability to predict extreme rainfall days (ERDs) in Myanmar, a country frequently affected by severe flooding due to intense rainfall. We used a physics-based model combined with real-world data to forecast ERDs based on the atmospheric ERA5 reanalysis data and records rainfall from 79 different stations in Myanmar. The findings reveal that ERDs are more common in specific regions of Myanmar during certain seasons and are associated with particular atmospheric conditions. In June and July, El Niño's rapid growth phase—which was linked to a large anticyclone anomaly over the Indian Ocean—caused an increase in ERDs in central Myanmar. The region experiences higher rainfall as a result of this anomaly's enhanced moisture transfer. Similar to this, a zonal SLP dipole in eastern Myanmar contributes to higher ERDs from April to September. Additionally, the study finds indicators of possible causation, such as SST anomalies and the SIO dipole index, that are precursors to higher ERDs. Using these physical indicators, prediction models with strong TCC values for monsoon core region and northern Himalayas foothill region of Myanmar at different times demonstrated notable accuracy. The study finds a strong correlation between summer ERDs and monsoon rainfall, indicating that predicting mean rainfall accurately is essential for forecasting ERDs. To comprehend and forecast future changes in these relationships, more research is necessary due to the non-stationarity of predictor-predictand interactions. The discovery clarifies important atmospheric variables that impact extreme rainfall episodes in Myanmar and advances our understanding of these occurrences.

Enhancing moisture transfer and quality attributes of tomato slices through synergistic cold plasma and Osmodehydration pretreatments during infrared-assisted pulsed vacuum drying

The present study examines the impacts of combined cold plasma treated water (PW) and osmodehydration (OD) pretreatment (PO), and operation parameters like PW duration and voltage of treatment on the dehydration, functional and sensory characteristics of sliced tomato fruits subjected to simultaneous infrared-assisted pulsed vacuum drying (IR-PVD). From the results, PO pretreatment modified the surface structures by the formation of microchannels and cavities through impingements from the reactive species (RS), and was improved due to increased treatment duration and voltage, and resulted in accelerating the transfer of moisture from the slices to the surroundings during the dehydration process. Consequently, PO pretreatment achieved an enhancement in the moisture diffusivity by up to 64.83%, shortened the total drying time by up to 40%, and presented substantial improvements in the physicochemical properties including vitamin C, lycopene, colour, total soluble solids, phenolic and flavonoid contents, and overall human acceptability. However, significant decreases in rehydration and hardness properties were shown compared with control, and higher rehydration by up to 21.66% at higher treatment duration and voltage when compared with OD pretreatment. Overall, PO pretreatment incited an effective moisture removal and retention of vital physicochemical and bioactive constituents in the slices due to the activities of plasma injected RS. This study provides an empirical basis for the application of PO during IR-PVD of fruits and vegetables and demonstrated as a suitable energy-saving alternative for improving the conventional OD of foods in the industry.

Shell structure impacts Camellia oleifera fruit splitting during dehydration

This study aims to enhance the processing efficiency of Camellia oleifera fruit by exploring the potential relationship between the splitting characteristics during the dehydration process and the structure of the C. oleifera shell. The analysis focused on understanding the structural changes, moisture transfer, and shrinkage strain of the C. oleifera shell during the shelling processes. The results indicate that the essence of shelling C. oleifera fruit is the uneven shrinkage strain of the shell after dehydration, with the uneven shrinkage of the mesocarp being the primary driving force for the separation of seeds from the shell. Because the cuticle prevents moisture transfer and epidermal cells limit shell shrinkage, the exocarp can restrict the efficiency of the shell shrinkage strain. By damaging the exocarp structure, the shelling efficiency of C. oleifera fruit can be increased by more than 50 % under both natural drying and hot air drying. Moreover, under hot air drying, the shelling efficiency of C. oleifera fruit with a damaged exocarp at a low temperature (55 ℃) is 12.5 % higher than that of undamaged fruit at a high temperature (75 ℃). This study provides new insights into improving the shelling efficiency of C. oleifera fruit.

The Effects of Polyester Filament Number and Accompanying Hydrophilic Fiber Type on Moisture Management and Drying of Double-Layered Knitted Fabrics

This study aims to investigate the moisture transfer and drying behavior of the double-layered fabrics knitted using polyester yarns with a combination of cotton and viscose yarns. As well as the fiber type on both faces, the effect of the number of filaments of the polyester yarns was also researched. For this purpose, double-layered interlock fabrics were knitted, and the resultant samples were characterized by moisture management, drying, water vapor permeability, and heat conduction tests. It was indicated that the fabrics knitted by polyester yarns on the inner side and cotton fabrics on the outer side resulted in a very good overall moisture-management capacity. The same applied to the drying speed; even faster drying was achieved than the 100% polyester double-layered samples. The increase in the filament number led to a decrease in both moisture management and drying rate. Moreover, it was determined that the use of viscose yarn was not suitable.

FEATURES OF WASHING WATER-SOLUBLE PHOSPHORUS-AMMONIUM SALTS OF FIREPROOF WOOD COATING

The article analyzes fire-resistant materials for wooden building structures and establishes the need to develop reliable methods of researching the process of washing out flame retardants from the surface of the building structure, which are necessary for the creation of new types of fire-resistant materials. Therefore, there is a need to determine the conditions for the formation of a barrier for leaching and to establish a mechanism for inhibiting the transfer of moisture to the material. In this regard, a mathematical model of flame retardant leaching has been developed, when a polymer shell made of organic material is used as a coating, which allows evaluating the effectiveness of the polymer shell based on the amount of flame retardant washed out. According to experimental data and theoretical dependences, the dynamics of release of flame retardants from the fire-resistant layer of the coating, which does not exceed 1.0%, is calculated, and accordingly provides fire protection of wood. The results of determining the loss of mass of the sample during exposure to water indicate an ambiguous effect of the nature of the protection on leaching. In particular, this assumes the availability of data sufficient for qualitatively carrying out the process of inhibiting moisture diffusion and identifying, on its basis, the moment in time when the decline in coating efficiency begins. Experimental studies have confirmed that a sample of fire-resistant wood after exposure to water for 30 days withstood the influence of heat flow. In particular, the loss of wood mass after temperature exposure was less than 6%, and the temperature of flue gases did not exceed 185 ºС. Thus, there are reasons to assert the possibility of targeted regulation of wood fire protection processes through the use of polymer coatings capable of forming a protective layer on the surface of the fire retardant material, which inhibits the rate of flame retardant leaching.

Numerical modeling of biophilic design incorporating large-scale waterfall into a public building: Combined simulation of heat, air, and water transfer

Biophilic design, which integrates nature into built environments, fosters beneficial human–nature interactions. It has gained traction as a promising solution to achieve a better trade-off between sustainability and occupants' well-being. However, despite its potential, quantitative assessment of biophilic design, particularly water elements, remains limited. This study addresses this gap using a two-step approach that quantifies the effects of biophilic water design on indoor hygrothermal conditions. We first developed a numerical model that couples building energy simulations with computational fluid dynamics to accurately predict the heat, air, and water transfer phenomena caused by waterfalls and ponds, and a novel mathematical model that precisely calculates water evaporation using water potential as the driving force of moisture transfer. Then, using this proposed method, we performed a numerical analysis of an actual public building as the reference space. This analysis quantitatively evaluated the effects of water elements on a hygrothermal environment and their impact on energy conservation. A series of comparisons and discussions based on the simulation results demonstrated the model's capability to accurately simulate the hygrothermal environment influenced by waterfalls and ponds. Moreover, the study confirmed and quantified the effects of waterfalls, specifically its significant evaporative cooling effect during summer, humidifying effect in winter, and heat load reduction benefits. These findings enrich our understanding of the impacts of biophilic water design on indoor environments and energy conservation, thereby contributing to the optimization of biophilic design practices.

Predicting optimal flipping conditions during burger pan cooking with a numerical model

This study analyzes the influence of the number of flips on the cooking performance of burgers by heating contact using results from both experimental test and computational simulation. The analysis employs a previously developed multiphysics model that accounts for heat and moisture transfer as well as product deformation. The turning process was simulated considering two heat sources representing the cooking pan that are alternately activated and deactivated to heat either surface of the product. Furthermore, a set of experiments were carried out to validate the model outcomes recording data of temperature at the center and upper surface of the burger, weight loss, and shrinkage at different number of flips. When performing only one flip, great moisture expelling was observed at the top surface, while multiple flips facilitates moisture retention, reducing cooking losses and shrinkage since it allows for a reduction in cooking time to reach the desired temperature. However, more than five flips do not significantly improve these effects.

Size Effects in Climatic Aging of Epoxy Basalt Fiber Reinforcement Bar.

The purpose of this study was to obtain information on the influence of the size factor on the climatic aging of circular fiber plastics produced by pultrusion. The kinetics of moisture transfer was obtained in humidification and drying modes at 60 °C in samples of epoxy basalt fiber reinforcement bars: after 28 months of exposure in the extremely cold climate of Yakutsk and 30 months of exposure in the moderately warm climate of Gelendzhik. It was shown that the 2D Langmuir model adequately describes the kinetics. The diffusion coefficients in the reinforcement direction for bars with diameters of 6, 8, 10, 16 and 20 mm turned out to be significantly higher than in the radial direction. To clarify the aging mechanism of the bars and the tensile, compressive and bending strength, the coefficient of linear thermal expansion and the glass transition temperature of the epoxy matrix of the bars with a diameter of 6, 8 and 10 mm after 51 months of exposure in Yakutsk and 54 months of exposure in Gelendzhik were measured. It was shown that after climatic exposure, the deformability of the bars decreased with increasing diameter of the bar; the glass transition temperature increased more significantly in the bar with a smaller diameter. In 6 mm diameter bars, the compressive and bending strength limits decreased by 10-25 % due to the plasticizing effect of moisture. With the same depth of moisture penetration into the volume of the samples, its effect on the strength of thin bars was significant, and for thick bars, it was insignificant. An increase in the glass transition temperature by 6 °C, associated with the additional curing of the polymer matrix, occurred in the surface layer of the epoxy basalt fiber reinforcement bars and was revealed in bars with a smaller diameter.

Pulsed vacuum drying of fruits, vegetables, and herbs: Principles, applications and future trends.

Pulsed vacuum drying (PVD) is a novel vacuum drying method that has demonstrated significant potential in improving energy efficiency and product quality in the drying of foods and agricultural products. The current work provides a comprehensive analysis of the latest advancements in PVD technology, including its historical development, fundamental principles, and mechanistic aspects. The impact of periodic pulsed pressure changes between vacuum and atmospheric pressure on heat and moisture transfer, as well as structural changes in foods at micro- and macro-scales, is thoroughly discussed. The article also highlights the influential drying parameters, the integration of novel auxiliary heaters, and the applications of PVD across various fruits, vegetables, and herbs. Furthermore, the review examines the current status and needs for mathematical modeling of PVD processes, identifying key challenges, research opportunities, and future trends for industrial application. The findings suggest that PVD not only enhances drying efficiency and reduces energy consumption but also preserves the nutritional value, color, and texture of dried products better than traditional methods. Future research should focus on optimizing process parameters and integrating advanced control systems to further improve the scalability and applicability of PVD technology in the food industry.

The study on the coupled influence of water saturation on heat and mass transfer processes within porous media under CW laser irradiation

Continuous wave (CW) laser irradiation induces temperature changes in various phases within porous media, accompanied by phase change and gas transport. Water saturation is a crucial factor influencing this context's moisture and heat transfer process. This paper addresses this issue by establishing a theoretical model for CW laser irradiation on unsaturated porous media. Through experiments and simulations, it studies the effects of different water saturations on heat and mass transfer under laser irradiation. The results indicate that the critical depth reflects the influence of water saturation under laser irradiation on the distribution of solid-phase temperature in both time and space dimensions. Specifically, an increase in water saturation enhances the uniformity of solid-phase temperature distribution, while the gas temperature exhibits a similar distribution pattern. For mass transfer processes, it increases the evaporation rate and Darcy velocity of porous media within the effective range of laser irradiation. Lower water saturation facilitates phase change processes and accelerates gas transport rates. Importantly, this trend remains consistent even with the emergence of dry-saturation zones. Additionally, the decrease in water saturation has a coupled promoting effect on gas temperature and mass transfer processes. Lowering water saturation can increase gas temperature and consequently enhance mass transfer processes. Simultaneously, enhancing mass transfer processes benefits heat exchange between the two phases. In the four sets of experiments, the conformity of the surface temperature rise curves obtained from experiments and simulations is good, indicating that the model can accurately reflect the temperature rise patterns of sand particles. In summary, this work provides valuable research results on the effects of different water saturations on laser irradiation-induced temperature rise, phase change, and gas and moisture transport within porous media. It lays a specific theoretical foundation for laser soil remediation technology.

Prediction of thermal regime and frost heave deformations of subgrade soils during non-stationary heat and moisture transfer

In order to ensure the safe operation of high-speed trains in cold regions, frost heave is one of the basic problems in the research for prediction and control roadbed deformation in such regions. In this paper, based on the classical hydrodynamic model we developed a method of studying thermal regime of soils and predicting frost heave deformations of subgrade soils. Our coupling model takes into account the mutual influence of temperature and soil moisture during non-stationary processes of heat and moisture transfer, calculation of frost heave deformation based on calculated result of the temperature and moisture fields of the roadbed. We have also observed the change of the soil temperatures and frost heave deformation in a freezing-thawing cycle at the geodesic center of PGUPS. The field observation results show that the soil temperature variations amplitude decreases with depth. The simulation verification results and the field observation data show good reproducibility, thus the reliability of the model is confirmed. At last, the paper presents the application of the method in improving high speed railway lines (HSRL) subgrade design in order to reduce frost heave deformations. Based on the results of calculations, it is recommended to lay a thermal insulation layer at the depth of 0.2 m below the subgrade and on the slopes to reduce frost depth and frost heave deformations of subgrade soils.

Humidity-Controlling Ceramic Bricks: Enhancing Evaporative Cooling Efficiency to Mitigate Urban Heat Island Effect

Passive evaporative cooling technology using the building envelope is a crucial measure to mitigate the urban heat island effect. This study aims to enhance the cooling efficiency of the surface of enclosure structures by utilizing volcanic ash, potassium–sodium stone powder, and silica-based mesoporous oxide (SMO) as primary materials. These components are incorporated into the ceramic brick production process to create innovative humidity-controlling ceramic bricks (HCCTs). This study extensively investigates the impact of SMO and the amount of applied glaze on the physical and mechanical characteristics of these HCCTs. Additionally, it examines the water absorption and evaporative cooling properties of the studied materials under optimal substitution conditions. Numerical calculations are used to determine the heat and moisture transfer properties of HCCTs. The results indicate that incorporating 2% SMO and applying 70 g/m2 of glaze results in a moisture absorption capacity of 385 g/m2 and a moisture discharge capacity of 370 g/m2. These conditions also yield a notable flexural strength of 15.2 MPa. Importantly, the HCCTs exhibit significantly enhanced capillary water absorption and water retention capabilities. Increased water absorption reduces surface temperature by 2–3 °C, maintaining the evaporative cooling effect for 20 to 30 h. It is also found that the temperature of HCCTs decreases linearly with increasing water content and porosity, while the temperature difference gradually decreases with thickness. Water migration in HCCTs with greater thickness is notably influenced by gravity, with water moving from top to bottom. Therefore, it is recommended that brick thickness does not exceed 15 mm.

Influence of materials and surface parameters on the moisture buffering in office buildings: A sensitivity analysis of China

The management of indoor humidity through equipment consumes massive energy, leading to the growing interest in passive regulation of indoor humidity via moisture buffering. Numerous factors may impact the performance of interior finishing material during moisture regulation, thus identifying the dominant parameters is critical for moisture buffering effect optimization. This study analyzes the influence of five moisture and surface parameters, which are directly related to the moisture transfer of the interior finishing layer, on the thermal loads in a typical office building under typical climates in China. The analysis employs scatter plots and sensitivity indices based on Sobol's method. The results show that the material thickness plays a decisive role under different climates. The importance of sorption isotherm varies with climates and load types. The vapor diffusion resistance factor of the material only affects the latent heat loads, while the effect of the surface vapor transfer resistance is negligible. Finally, this study puts forward suggestions for interior finishing material selection to achieve low-load performance based on the characteristics of parameter combinations.

Simultaneous heat, moisture, and salt transfer in porous building materials considering osmosis flow: Part 1: Theoretical modeling based on nonequilibrium thermodynamics

Salt weathering is a common deterioration phenomenon that affects outdoor cultural properties, and it is important to precisely predict the heat, moisture, and salt transfer in porous materials to suppress salt weathering. Osmosis and osmotic pressure were considered in the field of soil research, especially in clay research, but not in the field of outdoor cultural properties and building materials, which are the main target of salt weathering. Osmosis in clay is supposed to be caused by its surface charge. However, it has been suggested that sandstones and bricks that constitute cultural properties and buildings also have surface charge as clay. Thus, osmosis and osmotic pressure can occur in building materials, which may lead to materials degradation. In this study, we derive basic equations, based on nonequilibrium thermodynamics, for the simultaneous heat, dry air, water vapor, liquid water, cation, and anion transfer in building materials by considering osmosis. This equation was compared with existing model for heat and moisture transfer equations as well as models that considered the salt transfer. Based on the previous research for osmosis in clay, we summarized conditions under which osmosis occurs in building materials and presented an outlook for modeling the physical properties of materials related to osmosis.

Thermal performance of energy piles in unsaturated soils: Experiment, simulation, and case study

The operation of energy piles in unsaturated soils involves coupled heat and moisture transfer, demanding further detailed investigation. In this paper, laboratory tests were conducted to validate a numerical model that incorporated vapor and liquid migration, convection, and latent heat transfer in unsaturated soils. Moreover, this model captured the dynamic variation in characteristic parameters of unsaturated soils. Building upon this observation, this study delved into the thermal performance of the energy pile under ten-year cooling and heating cycles, specifically focusing on the temperature, heat exchange rate, volumetric water content, and thermal conductivity. It is demonstrated that the imbalanced cooling and heating load adversely affects the long-term operation. In particular, the cooling power experiences a reduction of 15.1% after ten years of operation. The results indicate that higher soil temperatures positively impact the heat exchange rate in heating mode, while rainfall facilitates heat transfer in both seasons. Furthermore, a case study of an energy pile system was carried out, encompassing load calculation, pile group simulation, economic analysis, and design optimization. A comprehensive evaluation of the technical and economic feasibility demonstrates that the system exhibits excellent performance, particularly when the ratio of cooling and heating loads ranges from 1.1 to 1.3.

Assessing the performance of three experimental methods to investigate air path inside wall assemblies

Air leakages in buildings’ envelopes can lead to an over-consumption of energy and to additional issues such as moisture damage and poor indoor environment. The leakage air flow rate is usually assessed at the building scale using a pressurization test and leakage locations are commonly detected by infrared thermography or smoke. However, little is known about the air paths within wall assemblies, despite the need for detailed experimental data to validate numerical models for the coupled heat, moisture and pollutants transfers. One of the reasons is the difficulty to find adapted and robust experimental methods.In this paper, three experimental laboratory approaches are tested on simple light-wall assembly configurations: the implementation of three-dimensional grids of thermocouples and relative humidity sensors within the wall, and the use of a micro-particle tracer. The results are compared with each other as well as with numerical simulations.It was found that thermocouple grid has limited intrusiveness, good accuracy and response time but results are subject to flow fluctuations. Moreover, heat capacity and conductive transfer within materials complicate the correlation between heat and air transfers. Humidity sensors grid avoids the latter issue but is intrusive, overestimating air dispersion. The micro-particle tracer has the advantage of being non-intrusive and less impacted by flow fluctuations but its ability to track the air flow is strongly linked with the insulation filtration properties and the flow velocity. Overall this method seems to provide the best results but it is also the most complex and time-consuming one.

Hygrothermal Performance of Enclosures in a Storage Room and Energy Efficiency in Environmental Control

ABSTRACT This study aims to provide energy-efficient strategies for collections care in the face of financial and environmental challenges. Focusing on paper-based enclosures in storage rooms, the research proposes strategies to enhance energy efficiency by relaxing tight environmental controls. The five-stage process began with a standard test of hygrothermal properties and buffering capacity of the enclosures. In the second stage, a computer model was developed using the first stage results. This model was used in a series of specially designed tests simulating the transient heat, air, and moisture transfer between the room and enclosure to determine an acceptable room environment in which the enclosure conditions could meet collections care standards. The modelling results were used, in the third stage, to develop an AI model that predicted the enclosure conditions using room temperature and relative humidity (RH) inputs. In the final stage, a model for energy consumption of air-conditioning system operations was developed to predict across various control accuracies. Results indicate that the tight maintenance of room RH levels can be relaxed from 47–53% to 33–65%, with a corresponding reduction in energy consumption of approximately 16–18%. This relaxation, while maintaining enclosure conditions in line with conservation standards, was demonstrated through a simulation case at the National Library of Scotland. This study underscores the broader applicability of the developed procedure, asserting its relevance for cultural institutions seeking energy-saving potential through customized enclosure models.

Research on melon cascade drying technology to improve food safety

Abstract The aim of the study is to study the process of cascade drying of melons. The prospects for the implementation of the melon drying process using IR convective heat supply are substantiated. Intensification of moisture transfer occurs due to pre-pulse IR treatment of high density power heat flow. The effect of heat flux emitted by IR lamps on the object of study was studied. Analyses have shown that in the proposed method, under the influence of IR rays, there is an intensive removal of moisture from the entire volume of the material. A decrease in air temperature leads to an increase in the duration of the drying process. And an increase in the density of the heat flux leads to overheating of the surface of the material layer.

Drying time of plaster within in-fill plasterboard walls and evaporation theory for water within gypsum: methodology, numerical simulation and application

ABSTRACT The desulphurisation-gypsum-filling-wall (DSG-FW) formed by pouring into plasterboard partitions with desulphurisation gypsum slurry can utilise low-quality desulphurisation gypsum and also improve the acoustic insulation issues arising from the use of hollow partitions. The construction schedule of this wall is unable to be controlled because the moisture transfer characteristics in DSG-FW are unclear. Therefore, it is important to determine the drying time and the moisture-transfer behaviour during the construction process. By using different thicknesses of gypsum samples, adding different amounts of perlite and adjusting the relative humidity, whether the gypsum board is covered, the drying and evaporating process of gypsum was compared and analysed. The evaporative characteristics of the desulphurisation gypsum core wall at different relative humidities were determined through experiments. In addition, an evaporation model was introduced for simplification and verification. The experimental results show that the drying of gypsum is correlated with relative humidity and gypsum thickness: the higher the relative humidity, the lower the evaporation rate; the thicker the gypsum, the longer the drying time; perlite and gypsum board have no effect on gypsum drying. The rate of evaporation of DSG-FW increases non-linearly with the decrease in relative humidity under which the DSG-FW is conditioned; the simplified Hertz-Knudsen-Langmuir (HKL-S) model can only be used to predict the evaporation behaviour within the higher relative humidity range (more than 55% RH), while the simplified statistical rate theory (SRT-S) model was verified as being able to predict the rate of evaporation across almost the whole relative humidity range. The SRT-S model can be used to predict and control the construction of DSG-FW in actual engineering work.