Moisture Diffusion Coefficient Research Articles

Investigation of drying kinetics, color, and rehydration parameters of broccoli florets dried with infrared radiation following blanching pretreatment

In order to reduce the drying time of broccoli and to investigate rehydration and color changes associated with the drying process, infrared drying method and blanching pretreatment were used in this study. Boccoli florets were dried using infrared drying at power levels of 50, 62, 74 and 88 W to investigate drying kinetics. Blanching was used as a pretreatment and it was found that the blanched samples dried faster. Effective moisture diffusion coefficients were also calculated. While Deff values between 9.26 × 10−11 and 2.15 × 10−10 m2/s were observed for the control samples, this value varied between 1.10 × 10−10 and 2.87 × 10−10 m2/s for the blanched samples. The calculated activation energy values for the blanched and control samples are 2.11 and 2.0 kW/kg, respectively. The drying process was modeled using 12 different thin-layer drying models and it was found that the Midilli & Kucuk model best represented the process. Color analysis was performed by measuring L, a and b values as well as chroma, hue angle and total color change values. It was observed that increasing infrared power affected color parameters, leading to a decrease in L values and an increase in a and b values. In addition, blanching pretreatment preserved color to some extent. The rehydration behavior of dried samples was also analyzed. It was found that the highest rehydration capacity was achieved in blanched samples dried at 74 W.

Drying Kinetics and Sorption Isotherms of Biocomposite Materials: Experimental Investigation and Modeling Analysis.

Modern materials science has made significant progress in creating new materials and processes for waste recovery. One such advancement involves the development of a new porous composite material made from clay and an environmentally sustainable eggshell powder. In this study, the dynamic behavior of water vapor during desorption and adsorption processes within this composite material was investigated. The moisture diffusivity coefficient was determined within the clay/eggshell powder composite material. The drying kinetic data were analyzed using various models such as Newton, Page, and Wan and Singh. The static gravimetric vapor adsorption/desorption experiments were conducted at different temperatures (30, 40, 50, 60, and 70 °C) to depict the material's capacity for absorbing and releasing moisture over time. The experimental isotherm data were fitted using different mathematical models (Guggenheim, Anderson, and De Boer, Peleg, Adam and Shove, Oswin, and Modified Henderson). The findings suggest that integrating eggshell powder with clay can significantly influence the behavior and characteristics of the resultant material. The combination of eggshell powder and clay reduces moisture sorption and accelerates the drying process. Consequently, this affects the porosity, permeability, and response to humidity changes.

Microwave drying characteristics and kinetics of hematite pellets

Microwave drying characteristics and kinetics of hematite pellets were investigated based on evaluation of the effects of initial mass, microwave power and pellet size during the drying process. The results showed the average drying rate increased with initial mass from 50 g to 80 g and microwave power from 600 W to 1000 W. However, it decreased with increasing pellet size from 10–12 mm to 14–16 mm. The process was successively controlled by external diffusion, internal diffusion, and chemical reaction. The Verma model was the most suitable kinetic model for describing the process. The effective diffusion coefficient of moisture ranged from 6.61 × 10−7 m2/s to 9.98 × 10−7 m2/s. The activation energy for the microwave drying process was only 2.83 W/g.

Influence of humidity fluctuations in the chamber on the calculated values of the moisture diffusion coefficient in wood

Influence of humidity fluctuations in the chamber on the calculated values of the moisture diffusion coefficient in wood

Investigation into diffusion behaviours of moisture in asphalt film using Fourier transform infrared spectroscopy

ABSTRACT To reveal the moisture damage mechanism of asphalt pavement and clarify the process of moisture damage to asphalt films, the diffusion behaviours of moisture in asphalt films were analysed. The findings indicate that during the first stage of the water bath process, the moisture diffusion coefficient in asphalt films is considerable and the diffusion rate is rapid. As the moisture diffusion rate increases, the free moisture content in asphalt films tends to saturate. Subsequently, partial free moisture transitions into bound moisture results in a decline in the diffusion coefficient of asphalt films and a reduction in its moisture absorption rate. As the temperature rises, the moisture diffusion coefficient in asphalt film and the maximum saturation amount of moisture that can be absorbed by asphalt films increase. The moisture diffusion behaviour is not readily discernible at a low temperature. The diffusion coefficients of moisture in unmodified asphalt films in the two stages are higher than those in modified asphalt films. The first stage of moisture diffusion in unmodified asphalt films occurs at a faster rate than in modified asphalt films. It is further verified that unmodified asphalt is more subjected to moisture damage.

Effect of Radio Frequency Vacuum Drying on Drying Characteristics and Physicochemical Quality of Codonopsis pilosula Slices

In this study, the radio frequency vacuum drying (RFVD) technique was used to dry Codonopsis pilosula slices. The effects of the drying temperature, slice thickness, plate spacing, and vacuum degree on the drying characteristics and physicochemical properties of the slices were investigated. The results showed that as the drying temperature and vacuum degree increased and the slice thickness and plate distance decreased, the drying rate and effective moisture diffusion coefficient of the Codonopsis pilosula slices improved, and the required drying time was shortened by 11.11% to 29.41% compared to that after hot air drying (HAD). Through comparison, it was found that the Midilli and Weibull models could better describe the moisture variation trend during the RFVD of Codonopsis pilosula. After RFVD, the retention of lobetyolin and syringin in Codonopsis pilosula significantly increased, with maximum contents of 135.74 mg/100 g and 19.16 mg/100 g respectively, which were 75.2% and 124.28% higher than those obtained by HAD. The contents of polysaccharides, total phenolics, and total flavonoids and antioxidant performance were also enhanced. The color, shrinkage rate, and internal tissue structure were significantly improved. In conclusion, RFVD not only increases the drying speed of Codonopsis pilosula slices but also ensures the good quality of the dried products.

ЦЕЛЕСООБРАЗНОСТЬ ПРИМЕНЕНИЯ ПРЕДВАРИТЕЛЬНОГО ОЗОНИРОВАНИЯ ВЛАЖНОГО ЗЕРНА ПЕРЕД СУШКОЙ

When drying grain, ozone enters into a number of chemical reactions that contribute to an increase in the partial pressure inside the grain and a change in the temperature gradient, which accelerates vaporization and increases the moisture diffusion coefficient. Practical application of the ozone-air mixture as a drying agent has not been established due to difficulties with process safety, the lack of substantiated ozone treatment modes, and imperfect ozonizer designs. The feasibility of using the ozonation process during drying was determined based on experiments on changing grain moisture using the ozone-air mixture as a drying agent. It was proposed to modernize the existing grain drying complexes by retrofitting the buffer silos with an ozonation system. A method for drying grain material has been developed that consists of two sequentially performed operations: preliminary ozone treatment of wet grain and its subsequent drying in a serial grain dryer. Three experiments were conducted to determine the effect of preliminary ozonation on the moisture separation process when heating a grain heap. It was found that the use of preliminary ozone treatment of wet grain in a buffer tank before the grain dryer with an ozone concentration of 5, 7.5 and 15.3 mg/m3 made it possible to increase the relative drying rate by 1.51-1.84 times. Preliminary ozonation of wet grain is advisable because it not only reduces the costs of bringing the grain to a conditioned state in terms of moisture, but also has a positive effect on the quality of the dried material.

Effect of Far-Infrared Drying on Broccoli Rhizomes: Drying Kinetics and Quality Evaluation

To clarify the effects of far-infrared drying technology on the drying kinetics and quality of broccoli rhizomes, broccoli rhizomes were dehydrated at 60, 65, 70, 75 and 80 °C, respectively. Eight thin-layer drying mathematical models were used to explore the drying kinetic characteristics and comprehensively evaluate their quality. The results showed that the higher the drying temperature, the shorter the time required to dry the broccoli rhizomes to the endpoint, and the higher the drying rate. The drying temperature was 80 °C, the shortest drying time was 360 min, and the average drying rate was 4.72 g·g−1·min−1. The longest drying time at 60 °C was 660 min, and the minimum average drying rate was 1.99 g·g−1·min−1. The effective diffusion coefficients of moisture at different drying temperatures were 1.22 × 10−6, 1.25 × 10−6, 1.34 × 10−6, 1.46 × 10−6 and 1.55 × 10−6 m2/min, respectively. The activation energy was calculated to be 12.26 kJ/mol by the linear relationship between the effective moisture diffusion coefficient and time. From the thermodynamic parameters, the drying of broccoli rhizomes is a non-spontaneous process, and it is necessary to absorb heat from the medium to achieve dehydration. With an increase in the drying temperature, the drying effect is better. The fitting results of eight mathematical models showed that Modified Page, Page, and Wang and Singh were the best mathematical models for the far-infrared drying kinetics of the broccoli rhizomes. The membership function method comprehensively evaluated the quality of the broccoli rhizome dry products. The comprehensive order was 60 °C > 65 °C > 75 °C > 70 °C > 80 °C. When the temperature was 60 °C, the physicochemical properties and nutritional quality of broccoli rhizome were well preserved, and the quality was the best. Therefore, 60 °C is the best temperature for broccoli rhizome drying. The results provide a theoretical reference for further improving the far-infrared drying quality of broccoli rhizomes.

Effects of ultrasonic pre-treatment on the porosity, shrinkage behaviors, and heat pump drying kinetics of scallop adductors considering shrinkage correction

Shrinkage has a negative impact on drying efficiency and quality. However, insufficient information about the effect of shrinkage on drying kinetics hampers the comprehension of the underlying mechanism. This study aims to investigate the effects of ultrasonic (US) pre-treatment and drying conditions on volume ratio (VR), apparent density, and porosity, as well as drying kinetics with and without shrinkage correction of scallop adductors during heat pump drying. The VR and apparent density decreased, while porosity increased with higher drying temperatures and longer drying times. US pre-treatment resulted in decreased apparent density, but enhanced VR and porosity, demonstrating the effective role of US in alleviating shrinkage and promoting pore formation during drying. Ignoring shrinkage phenomenon caused a weak underestimation in drying efficiency but a significant overestimation in the effective moisture diffusivity coefficient. Therefore, shrinkage effect must be considered to properly comprehend drying behaviors. The mechanism of shrinkage was closely related to the glass transition theory. The critical moisture ratio at which the samples underwent a glass transition was increased by 15 % with US pre-treatment in comparison to the control. US-pretreated samples could achieve a glassy state more quickly than the control under the same drying conditions, leading to reduced volumetric shrinkage.

Quasi-static bending analysis of composite laminated cylindrical panels under hygrothermal conditions

The combined effects of temperature and humidity, termed hygrothermal, are included in the deformation analysis of laminated composite cylindrical panels based on first-order shear deformation theory (FSDT). The panel is under transverse mechanical load, and both steady-state and transient hygrothermal loads are considered. The problem is solved using the minimum potential energy theorem for different boundary conditions. The moisture profile through the thickness is obtained by analytical solution of Fick diffusion equation. The dependency of moisture diffusion coefficient on temperature is considered and the material temperature is assumed to be the same as the environmental temperature. Using a semi-analytical approach, displacement field of the panel subjected to evaluated profile of moisture in a specific time and thermo-mechanical loads is obtained. The accuracy and validation of the present solution are demonstrated by solving numerical examples and comparing them with the results available in the literature. Furthermore, new results are presented and effects of various important parameters such as panel geometry, edge boundary conditions, lamination layups and imposed moisture conditions on the deformation of the composite cylindrical panel are studied. Solved examples demonstrate that higher length-to-arc and radius-to-thickness ratios result in increased deflection and amplify the influence of mechanical load compared to hygrothermal effects on the overall deformation of the panel. In most case studies, the hygroscopic deformation observed at one-tenth of the saturation time exceeded half of the deformation observed after the saturation time, which shows the importance of transient hygroscopic analysis.

Identification of the potato moisture diffusion coefficient considering shrinkage: a nonlinear estimator approach to an inverse problem

Identification of the potato moisture diffusion coefficient considering shrinkage: a nonlinear estimator approach to an inverse problem

Study on the characteristics and kinetics of microwave hot air combined drying of peanut pods

Drying is an important means to maintain the quality of peanut pods and reduce the risk of mildew. Microwave hot air combined drying is renowned for its efficacy, low-energy consumption, and superior processing quality, rendering it suitable for peanut pod drying. However, its efficacy hinges greatly on various parameters. To enhance drying efficiency and quality, the drying kinetics of peanut pods using microwave hot air combined drying equipment were investigated. Varying microwave power (1.2 kW, 2.4 kW, 3.6 kW), hot air temperature (30 °C, 35 °C, 40 °C, 45 °C), air velocity (0.4 m/s, 0.7 m/s, 1 m/s), and microwave radiation time (4 min, 6 min) were examined. Results indicated a decline in drying time, moisture ratio, and drying rate with increasing microwave power, hot air temperature, air velocity, and microwave radiation time. Peroxide and acid values complied with national standards. The Verma model exhibited optimal fitting. At 45 °C, peanut pod moisture diffusion coefficient was 3.022 × 10−9 m2 s−1, specific energy consumption at 30 °C was 5302 kJ/kg, and thermal efficiency was 42.6 %. The synergistic drying of peanut pods by microwave and hot air has a high moisture diffusion coefficient and thermal efficiency. The kinetic and energy analysis of the drying process can furnish some theoretical foundation for subsequent microwave hot air drying and equipment parameter adjustment.

Development of an Apple Snack Enriched with Probiotic Lacticaseibacillus rhamnosus: Evaluation of the Refractance Window Drying Process on Cell Viability.

The objective of this study was to develop a dried apple snack enriched with probiotics, evaluate its viability using Refractance Window (RWTM) drying, and compare it with conventional hot air drying (CD) and freeze-drying (FD). Apple slices were impregnated with Lacticaseibacillus rhamnosus and dried at 45 °C using RWTM and CD and FD. Total polyphenol content (TPC), color (∆E*), texture, and viable cell count were measured, and samples were stored for 28 days at 4 °C. Vacuum impregnation allowed for a probiotic inoculation of 8.53 log CFU/gdb. Retention values of 6.30, 6.67, and 7.20 log CFU/gdb were observed for CD, RWTM, and FD, respectively; the population in CD, RWTM remained while FD showed a decrease of one order of magnitude during storage. Comparing RWTM with FD, ∆E* was not significantly different (p < 0.05) and RWTM presented lower hardness values and higher crispness than FD, but the RWTM-dried apple slices had the highest TPC retention (41.3%). Microstructural analysis showed that RWTM produced a smoother surface, facilitating uniform moisture diffusion and lower mass transfer resistance. The effective moisture diffusion coefficient was higher in RWTM than in CD, resulting in shorter drying times. As a consequence, RWTM produced dried apple snacks enriched with probiotics, with color and TPC retention comparable to FD.

Moisture migration mechanism of round bamboo in the radial direction during drying

Round bamboo exhibits a hierarchical gradient wall structure and contains closed bamboo cavities, creating a complex pathway for radial moisture migration. In this project work, round bamboo was dried at different temperatures (60, 75 and 90 °C), and the radial moisture content distribution and moisture migration pathway in the drying process were elucidated using the X-ray method, micromorphology and theoretical calculations. The porosity and average aperture of the inner bamboo internode were 38.92 % and 14.98 nm respectively, which were higher than those of the outer (23.17 % and 13.83 nm). The moisture diffusion coefficient at the bamboo diaphragm was about 1/4 that of the bamboo internode. The radial moisture content distribution in fresh round bamboo exhibited an asymmetric distribution, with higher levels in the middle and lower levels on both sides. During the drying process, moisture primarily migrated through the outer surface under the moisture gradient, with a small amount entering the bamboo cavity through the inner surface by temperature action. The moisture entering the bamboo cavity eventually migrated slowly through the diaphragm.

Drying Kinetics and Energy Consumption of Astragalus Membranaceus Under Infrared Drying

Abstract The Astragalus membranaceus (AM) slices was dried using three infrared drying techniques, including near-infrared drying (NIR), mid-infrared drying (MIR), and far-infrared drying (FIR). Studies and discussions about the impacts of infrared temperature, power, slice thickness, and wavelength on the drying properties, energy consumption, and associated performance were conducted. Results showed that the drying rate increased with increasing infrared temperature and wavelength, and with decreasing slice thickness, whereas the drying process was not significantly influenced by the infrared power. The drying efficiency of FIR was superior to that of NIR, and with the increase in temperature, this improvement became more obvious. FIR drying was the fastest with the least energy consumption among the three drying methods. Rehydration ratio and color change of AM slices were proportional to infrared temperature and wavelength, but inversely proportional to slice thickness. The effective moisture diffusion coefficients of AM slices under NIR and FIR drying ranged from 0.49244 × 10−9 to 1.16352 × 10−9 m2/s and 1.00432 × 10−9 to 2.51135 × 10−9 m2/s, respectively.

Instant controlled pressure drop (DIC) as an effective pretreatment to intensify drying efficiency and enhance quality attributes of heat pump dried scallop adductors

Scallop adductors (SA) with a moisture content (MC) of 65% (H-65), 55% (H-55), 45% (H-45), and 35% (H-35) were subjected to an instant controlled pressure drop (DIC) pretreatment to investigate its influence on the subsequent heat pump drying kinetics and quality attributes. SA without DIC was performed for comparison (CK). Compared to the CK, DIC resulted in a decreasing rate of 5.88–35.29% in the drying time, but an increasing rate of 11.12–46.89% in effective moisture diffusivity coefficient depending on samples' MC. After DIC, SA showed a decrease in α-helices and β-turns, but an increase in β-sheets, and a sharp decrease in the relaxation time and proportion of the immobilized water. DIC increased total color difference (expect H-45), hardness, rehydration ratio, but decreased shrinkage rate (except H-65) compared to the CK. DIC is a promising pretreatment for intensifying drying efficiency, inhibiting volume shrinkage, and improving rehydration capacity of SA.

Drying kinetic, thermodynamic and quality analyses of infrared drying of truffle slices.

Kinetic and thermodynamic parameters are the most important part for making a suitable tool for drying agricultural products. Moreover, calculation of the energy required for the drying of product, the properties of the rehydration ratio, the food appearance changes, and the evaluation of the microstructure of food are crucial. Since the thermodynamic properties of truffle slices have not yet been reported, this study aims to establish a mathematical model to describe drying process of agriculture product, evaluate the effective moisture diffusion coefficient (Deff), determining the activation energy (Ea) to elucidate the thermodynamic characteristics, measure color characteristics, and rehydration ratio (RR) during the drying process of truffle slices. Truffle slices were dried in an infrared (IR) dryer at four temperatures of 50-80°C and two thicknesses of 0.5 and 1cm. The best model to describe the drying process of truffle slices was Midilli etal.'s model. The value of Deff, SEC, and RR were in the range of 3.06 × 10-8 to 2.48 × 10-7 m2/s, 79.68-191.271kWh/kg, and 5.99-7.49, respectively. The Deff of truffle slices increased with the above-mentioned parameters of the samples. The Ea obtained was 26.62-27.43kJ/mol. The results indicated that enthalpy and entropy decreased with increasing drying temperature, while Gibbs free energy improved. The enthalpy, entropy, and Gibbs free energy values changed between 24.48-25.28kJ/mol, -130.47 to -122.63 J/mol °K, and 63.97-70.17kJ/mol, respectively. In addition, the results of color attributes decreased with increasing temperature, while chroma oppositely increased.

Combined refractance window and far infrared radiation drying of Spirulina platensis biomass: Drying behavior, moisture and thermal diffusivity, and biochemical characterization

A 2 mm thin layer of wet Spirulina platensis biomass was dried using two methods: refractance window drying (RW) and combined RW and FIR drying (RWF). The effect of drying temperature (40–60 °C) and proximity to FIR heaters (5 and 10 cm) was evaluated on falling rate drying characteristics. The moisture (Deff) and thermal (α) diffusivity coefficients were obtained in the range 1.728 × 10−8 to 5.289 × 10−9 and 1.322 × 10−8 to 4.169 × 10−9 m2 s−1, respectively (R 2, 0.921–0.984). RW drying at ≥50 °C caused loss of color, phytopigments, and lipid peroxidation. At 40 °C, RW drying led to a long drying period (300.50 ± 3.53 min), poor drying rate (0.039 ± 0.002 g-H2O/min), lowest Deff and α (5.289 × 10−9 and 4.169 × 10−9 m2 s−1), and chlorophyll loss (32.2%). Combined RW and FIR drying at 40 °C and 5 cm proximity (RWF40-5cm) reduced drying time (15.1%), increased drying rate (27.8%), improved α (15%), and Deff (14.9%). RWF40-5cm dried biomass showed excellent retention of color (ΔE = 4.64 ± 1.32), protein (93.8%), γ-linolenic acid (90.1%), chlorophyll (87.9%), and phycocyanin (86.7%) from freeze-dried biomass (FD). Low-temperature RWF40-5cm drying could be a potential alternative to freeze-drying for effective and safe drying of heat-sensitive Spirulina platensis biomass.

The Mathematical Modeling, Diffusivity, Energy, and Enviro-Economic Analysis (MD3E) of an Automatic Solar Dryer for Drying Date Fruits

Date fruit drying is a process that consumes a significant amount of energy due to the long duration required for drying. To better understand how moisture flows through the fruit during drying and to speed up this process, drying studies must be conducted in conjunction with mathematical modeling, energy analysis, and environmental economic analysis. In this study, twelve thin-layer mathematical models were designed utilizing experimental data for three different date fruit varieties (Sakkoti, Malkabii, and Gondaila) and two solar drying systems (automated solar dryer and open-air dryer). These models were then validated using statistical analysis. The drying period for the date fruit varieties varied between 9 and 10 days for the automated solar dryer and 14 to 15 days for open-air drying. The moisture diffusivity coefficient values, determined using Fick’s second law of diffusion model, ranged from 7.14 × 10−12 m2/s to 2.17 × 10−11 m2/s. Among the twelve thin-layer mathematical models, we chose the best thin drying model based on a higher R2 and lower χ2 and RMSE. The Two-term and Modified Page III models delivered the best moisture ratio projections for date fruit dried in an open-air dryer. For date fruit dried in an automated solar dryer, the Two-term Exponential, Newton (Lewis), Approximation diffusion or Diffusion Method, and Two-term Exponential modeling provided the best moisture ratio projections. The energy and environmental study found that the particular amount of energy used varied from 17.936 to 22.746 kWh/kg, the energy payback time was 7.54 to 7.71 years, and the net CO2 mitigation throughout the lifespan ranged from 8.55 to 8.80 tons. Furthermore, economic research showed that the automated solar dryer’s payback period would be 2.476 years.

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.