Drying Kinetics Data Research Articles

Drying kinetics and water adsorption properties of jalapeño pepper seeds (Capsicum annuum L.): A study aiming at their recovery and integral exploitation

Drying kinetics (DK) and water adsorption isotherms (WAI) of Jalapeño pepper seeds (JPS) were evaluated and modeled at different temperatures. The proximate composition, flavonoid content (FC), and total phenolic compounds (TPC) of JPS were determined. Furthermore, JPS oil was extracted and characterized. Five mathematical models were tested to describe the JPS drying kinetics at five temperatures (40–80 °C) as well as the effective diffusion coefficient (Deff) and activation energy (Ea) were calculated. The WAI of the JPS was determined at nine temperatures (8–72 °C) and five mathematical models were fitted to JPS adsorption data. Thermodynamic properties were also estimated. The JPS presented TPC (30.9 mg GAE/g), FC (17.4 mg catechin equivalents/g), fibers (54.8 g/100 d.b.), lipids (22.2 g/100 d.b.), and proteins (15.5 g/100 d.b.). The study on drying kinetics pointed out that the Weibull model best fitted to drying kinetics data, Deff increased directly to temperature, and the Ea = 30.302 kJ/mol. The GAB model presented good accuracy in describing the WAIs that were classified as BET Type II. The net isosteric heat of adsorption and differential entropy decreased with increasing EMC. Enthalpy-entropy compensation theory was corroborated and characterized the adsorption of JPS as enthalpy-driven and spontaneous.

A comparative assessment of drying kinetics, energy consumption, mathematical modeling, and multivariate analysis of Indian borage (Plectranthus amboinicus) leaves

AbstractIn the current study, four drying methods, namely microwave (MD), vacuum (VD), hot air (HAD), and freeze drying (FD), were compared for drying of Indian borage (Plectranthus amboinicus) leaves for optimum energy consumption and bioactive compounds' retention. Effective moisture diffusivity for MD was about 100 times more than that of HAD and VD. MD at 600 W showed minimum specific energy consumption (4.04 kWh/kg), proving the most suitable drying condition. Moreover, it showed desirable energy values in terms of maximum specific moisture extraction rate (0.265 kg moisture/kWh) and maximum drying efficiency (15.85%). Bioactive compounds' retention in terms of phenols, antioxidants, and flavonoids was better in MD, followed by FD. Mathematical modeling of drying kinetics data revealed proper fitting of three drying models, namely, Aghbashlo, Modified Page‐II, and Page model, for explaining the drying behavior of Indian borage leaves. Multivariate characterization using principal component analysis revealed that FD and MD had a strong effect on bioactive compounds' retention, while VD and HAD showed least effect. Hence, based on optimum energy utilization and bioactive compounds' retention, MD at 600 W was selected for efficient drying of Indian borage leaves.Practical applicationsDrying of Indian borage leaves using microwave drying (MD) resulted in quicker drying with retention of bioactive compounds and color of dried leaves. The energy aspects were also favorable for industrial scale‐up. With due consideration to capacity enhancement in MD, it can prove to be a promising source of drying for culinary, medicinal, and aromatic plants.

Study of the drying kinetics of black mulberry (Morus nigra L.) leaves

Black mulberry leaves have been used to promote health and prevent diseases due to their biological properties. Drying leaves allows greater stability during storage and marketing. However, studying this operation is important to ensure that the properties are maintained. Therefore, the objective of this study was to use mathematical modeling to define the model that best fits to the experimental data of the drying kinetics at temperatures of 40, 50, 60, and 70°C. Liquid diffusion, leaf surface area, the relationship between temperature increase and diffusion coefficient, and energy activation were also determined. Among the mathematical models studied, the Page model was the one that best described the drying process of black mulberry leaves. As for the diffusion coefficient, the values increase as the drying temperature increases. The activation energy was 65.418 kJ mol-1, and it was observed that the lower the activation energy, the greater the water diffusivity in the product. The drying kinetics data of black mulberry leaves allowed a better understanding of this operation in a matrix with wide application potential. Drying black mulberry leaves at different temperatures altered their color. Considering the evaluations, temperatures of 40 and 50°C are the most indicated for drying black mulberry leaves.

Convective drying of iron ore fines: A CFD model validated for different air temperatures and air velocities

In this research, a granular Eulerian multiphase model coupled with heat and mass transfer was used to simulate the convective drying process of iron ore fines. The CFD model was validated with experimental data for different air temperatures and air velocities. Convective drying experiments were performed using laboratory-scale equipment in order to obtain drying kinetics data for iron ore fines at air temperatures up to 140 °C and air velocities up to 15 m/s. The drying system had combined characteristics of fluidized bed and pneumatic transport. Numerical results showed good agreement with experimental data (average RMSE of 3.9 × 10−3) for the moisture content for nine drying air conditions. Since the coupled momentum, heat and mass transfer model could accurately and validly estimate the drying rate for iron ore fines according to the local conditions of the drying air in laboratory-scale equipment, it has potential for application in CFD simulations of industrial-scale equipment.

Current trends in cacti drying processes and their effects on cellulose and mucilage from two Colombian cactus species

The effect of temperature and drying technologies on mucilage and cellulose (obtained by the microwave-assisted extraction technique, MAE) from Opuntia ficus-indica (OFI) and Austrocylindropuntia cylindrica (CC) was determined using a conventional oven (CO) and Refractive Window (RW). Mathematical modeling was performed from drying kinetics data using the Lewis, Henderson-Pabis, Page, and Logarithmic models. Activation Energy (Ea) and Diffusivity (D) were also determined. The model with the best fit was the logarithmic one, with a correlation coefficient (R2) greater than 0.99. The obtained activation energies were 22.81 kJ mol−1 for Refractance window (RW) and 31.44 kJ mol−1 using conventional hot air drying (CO) while a diffusivity of 2.9 ∗10−8 m2 s−1 for RW and 1.3∗10−8 m2 s−1 for CO were found as well. According to our results, a greater drying efficiency and a less chemical deterioration of the plant sample are obtained by drying with Refractance window.

Application of Mathematical Models and Thermodynamic Properties in the Drying of Jambu Leaves

Jambu is a vegetable originally from the northern region of Brazil, has bioactive properties, being little explored by other regions, due to its high peresivity. And one of the methods to increase the shelf life of plant products is the removal of water. The objective of this work was to evaluate the drying kinetics of jambu leaf mass. Two treatments were carried out: The mass of fresh jambu leaves and the mass of fresh jambu leaves with the addition of drying foam, both submitted in an oven with forced air circulation at temperatures (50, 60 and 70 °C and thickness of 1.0 cm). The proximate composition of the materials was performed before and after drying. Twelve mathematical models were tested on drying kinetics data and thermodynamic properties were calculated. The parameters of the proximate composition for the mass of leaves and foam after drying were: Moisture content of (2 to 7%), ash content of (13 to 17%), protein content of (22 to 30%), lipids of (0.6 to 4%) and total titratable acidity (0.20 to 0.28%) of tartaric acid. The models that best fit the experimental data to describe the drying kinetics of jambu masses were: Wang & Singh. The use of foam mat presented higher values of effective diffusion coefficient and activation energy and lower values of enthalpy and entropy, reducing the drying time.

Drying kinetics of Brazil nuts

The drying is one of the stages of processing Brazil nuts, being an important stage due to the high moisture content and water activity of the product. This study aimed to adjust mathematical models to the drying kinetics data of Brazil nuts, calculating the effective diffusion coefficient and obtaining activation energy for the drying process. Brazil nuts were collected in amazon region, and then the product was homogenized for processing. The nuts were subjected to drying in a forced ventilation oven at temperatures of 40, 50, 60, 70 and 80 °C in 4 replicates, each one consisting of approximately 200 g of samples in aluminum containers. Mathematical models were adjusted to the experimental data of the moisture content ratio. Thompson, Midilli, Logarithmic and Two Terms models are suitable for estimating the drying of Brazil nuts. The Two Terms model was selected to represent the drying phenomenon for presenting better results in the analyzed parameters. The effective diffusion coefficient increased with increasing temperature and the activation energy for the liquid diffusion in the drying was 35.69 kJ mol-1.

Hot air convective drying of hog plum fruit (Spondias mombin): effects of physical and edible-oil-aided chemical pretreatments on drying and quality characteristics

This aim of this study was to evaluate the effects of pretreatments and temperature on the hot air drying characteristics of hog plum fruits. Hog plum fruits were pretreated with olive oil/K2CO3 or sunflower oil/K2CO3 at 28 °C and olive oil/NaOH cum blanching at 96 °C for 15s, hot water at 96 °C for 15s, and dried in a hot air drier at 50, 60, and 70 °C. Mathematical models were used to fit the data of drying and rehydration kinetics. Results showed that increase in temperature reduced drying time, increased effective diffusivity and shrinkage. Sunflower oil aided chemical pretreated sample had the shortest drying time (780 min) and highest effective diffusivity (6.3 × 10−8 m2/s) at 60 °C, faster rehydration ability at 60 °C, highest retention rate for ascorbic acid (15 %), phenolic content (29 %), and antioxidant activity (12.3 %), while olive oil aided chemical (K2CO3) pretreated sample had the shortest drying time at 50 °C (990 min) and 70 °C (600 min), lowest shrinkage (48.5 %), slower rehydration capacity at 40 °C, and lowest colour change (ΔE = 11.5). Modified Henderson and Pabis and Vega-Gálvez were superior to other fitting models in predicting the drying and rehydration kinetics. Sunflower oil/K2CO3 pretreatment could help improve the drying and quality characteristics of hog plum.

Use of diffusive and empirical models to predict drying rate of acerola seeds (Malpighia sp.)

The thin layer drying process of acerola seeds was analyzed using a flat plate geometry diffusion model, Page's model, and a two-part model proposed based on the diffusion equation. These models were fitted to experimental drying kinetics data of acerola seeds for an air flow speed of 1.5 m/s, at temperatures of 40, 50, 60 and 70°C, using non-linear regression by Levenberg-Marquardt method. The diffusion model was used to determine the diffusion coefficients and activation energy. The predicted and experimental results were compared using the determination coefficient (R2) and mean square error (MSE) of the estimates as criteria. The results showed that the diffusion model is not suitable for predicting the drying rate of acerola seeds, while Page’s equation and the two-part proposed model can be safely used to predict the drying rates.

Evaluation of the influence of ambient air temperature and air velocity on mortar cement durability using a forced convection solar dryer

PurposeThis work aims to study the hydrothermal behavior of mortar cement toward certain environmental factors (ambient air temperature and air velocity) based on its drying kinetics data. The objective is to provide a better understanding and controlling the stability of mortar structures, which integrate the sorption phenomenon, drying process, air pressure and intrinsic characteristics. This leads to predict the comportment of mortar structures in relation with main environmental factors and minimize the risk of cracking mortar structures at an early age.Design/methodology/approachThermokinetic study was carried out in natural and forced convection solar drying at three temperatures 20, 30 and 40°C and three air velocities (1, 3 and 5 m.s-1). The empirical and semiempirical models tested successfully describe the drying kinetics of mortar. These models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures.FindingsThe models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures. The average activation energy obtained expressed the temperature effect on the mortar diffusivity. The drying constant and the diffusion coefficient can be used to predict the influence of these environmental factors on the drying behavior of various building materials and therefore on their durability.Originality/valueEvaluation of the effect of several environmental factors and intrinsic characteristics of mortar structures on their durability.

THIN-LAYER DRYING FROM WASTES POMEGRANATE PEEL

Pomegranate juice processing produces a large amount of peel as a by-product or waste which is a potential source of raw material for food and other bioprocessing industries, such as(fights acne, pimples and rashes, helps in detoxification of body, cures sore throats and coughs, arrests hair loss and prevents dandruff, improves dental hygiene). Drying the peel offers opportunities for value addition into novel products, thus reducing amount of produced waste from the fruit processing operations. The dry parameter was drying air temperature (65, 75 and 85°C) and drying air velocity (1, 2 and 3 m/s) at layer thickness of 7mm. The results indicated that the initial moisture content of 244% (d.b) decreased to a range between 6 and 4% (d.b) at the end of drying process depending on the drying conditions. The results obtained show that moisture content of the by-product decreases with time and temperature. Two thin-layer drying models were selected to describe experimental drying kinetics data. The models were compared based on their coefficients of determination (R2), reduced chi square (χ2) and root mean square error (RMSE) between Observed and predicted moisture ratios. On the other hands, the calculated operation cost of the dryer approaches about 5.5 E/kg, while the price of 1 kg of dried pomegranate peel is 35 LE in the market.

Artificial neural networks to model kinetics and energy efficiency in fixed, fluidized and vibro-fluidized bed dryers towards process optimization

Drying of inorganic particulate compounds is recognized as an energy-intensive process. Due to this fact, optimization studies through modeling and simulation of experimental data play a critical role towards process economic benefits. The main drawback of some models from literature is their dependence on operating parameters and dryer type, which can be a key issue for data generalization. Artificial neural networks may provide the first step to solve this problem. This study analyses the feasibility of neural models to fit and estimate drying kinetics data, cumulative and instantaneous energy efficiency indices from fixed, fluidized and vibro-fluidized bed dryers at different operating conditions. The networks were trained considering different scenarios for both drying kinetics and energy analysis. It was shown that the neural model is consistent to estimate new patterns not addressed in the trainings for the case in which the database is regarded for a single type of dryer. Simultaneous training considering multiple datasets of each dryer resulted in predictions with poor accuracy, but considering the complex hydrodynamic conditions of the moving beds, there is room for improvement when efficient data is used. In this way, neural models can be considered an interesting tool to predict parameters also for energy analysis.

Modelagem matemática da cinética de secagem de cascas do kino (Cucumis metuliferus)

Objetivou-se com este trabalho realizar a caracterização química e física das cascas do kino (Cucumis metuliferus) bem como avaliar através da modelagem matemática a cinética de secagem em diferentes temperaturas. As cascas foram caracterizadas in natura quanto ao teor de água, sólidos totais e solúveis, atividade de água, cinzas, pH, acidez total titulável, Ratio e ácido ascórbico. Determinou-se a cinética de secagem nas temperaturas de 60, 70, 80 e 90 °C, ajustando os dados a doze modelos matemáticos utilizando como critérios de ajuste o coeficiente de determinação (R2) e o desvio quadrático médio (DQM). As cascas do kino apresentaram alto teor de água e atividade de água, com parâmetros de acidez e cinzas relativamente baixos e teores satisfatórios de ácido ascórbico, sólidos totais e solúveis. Dez dos modelos testados apresentaram ajustes satisfatórios aos dados da cinética de secagem, destacando-se os modelos de Page e Aproximação da Difusão, com R² > 0,999 e DQM < 0,091.

Modeling and kinetics study of novel microwave irradiation drying of naproxen sodium drug

Drying kinetics is vital to optimize and predict the moisture content and drying rate when designing drying systems for new drug products. In this work, drying kinetics was studied for naproxen sodium drug formulation dried using microwave radiation by measuring the drug moisture content and drying rate. Ten semi-theoretical and empirical thin layer models were tested for their suitability in representing the drying kinetics data at different levels of microwave power. The experimental results showed that the extent of moisture removal increased with increasing microwave power output. It took 35, 24 and 8 minutes to remove 90% of the original moisture content at 30, 60 and 90 W, respectively. The drying rate increased steeply with an increase in time to reach maximum values of 4.7, 6.9 and 11.1 kg/m2.min at 30, 60, and 90 W, respectively and then decreased to reach a constant value. Among the mathematical models tested, logarithmic model provided the best fit in representing the drying kinetics data for all microwave power values. Two new empirical models developed using experimental moisture content and drying rate data could estimate these two parameters with higher accuracy as a function of drying time and microwave power.

Kinetics of drying and stability of yellow passion fruit peel flour as a function of storage time and temperature

The use of the yellow passion fruit peel (Passiflora edulis) was evaluated to analyze the best conditions for drying the peels and to study the storage conditions of the yellow passion fruit peel flour. Moreover, the viability of the flour to develop new food products was evaluated, through the physicochemical analyses. Drying was carried out in a convective dryer at temperatures of 50, 60 and 70°C. The dehydrated peels were then ground in a knife mill to obtain flour. The results of the drying kinetics data were adjusted to the mathematical models of Brooker, Lewis, Fick and Residual, using nonlinear regression. The physico-chemical characteristics of peel and the flour were determined and the study on the best storage conditions of the flour were carried out during 100 days at three different temperatures: ambient, cooling at 10 and 0°C. According to the results, the Brooker and Lewis models obtained better adjustments for the drying kinetics of the peel at the temperature of 70°C, whose R2 was equal to 0.9804 and 0.9776, respectively. The physicochemical analysis revealed that the yellow passion fruit peel flour has a high protein content and high crude fiber content in its composition. Stability studies showed that the best storage condition of yellow passion fruit peel flour is at low temperatures.

Mass diffusivity of different species of wood in convective drying

This study is devoted to the determination of the diffusion coefficient in convective drying of four local wood species: Aleppo pine, Stone pine, Zeen oak and date palm. A numerical method based on a diffusive model is used which consists of three complementary steps: experimentation, analysis of experimental data and minimization of the gap between experimental drying kinetics data and calculated ones. The coefficient of water for the four wood species is considered depending on both temperature and moisture content, and is obtained by the numerical solution of the conservation equation of the solid phase and the water transfer equation coupled to the shrinkage rate of the solid phase. The found values of diffusion coefficient are consistent with the range of variation in the literature. The mass diffusion coefficient varies with increase in temperature between 1.510−11 and 4.10−11 (m2/s) for the Aleppo pine, Stone pine and Zeen oak woods, however for the “palm wood”, it varies from 10 to 11 to 6.10−11 (m2/s). Arrhenius type relationship allows determining the activation energy, which varies between 135.64 and 150.49 (kJ/mol) for all species of wood treated, and these values are comparable with those of other species cited in literature.

Drying kinetics of building materials capillary moisture

Drying of building materials capillary absorbed water is one of the main factors that determine buildings materials durability. Thus, the investigation of drying kinetics of capillary absorbed water can be very useful in understanding the causes of decay of building materials and in saving cost and improving the energy efficiency of constructions. In general, environmental conditions, such as air temperature, air velocity and air relative humidity, affect drying kinetics of various building materials.Most of the drying kinetics mathematical models use as initial moisture content the amount of water resulting by saturation of samples through immersion. In the present work, the drying process of capillary absorbed water, which describes more accurately materials behavior in buildings, was experimentally studied. An existing mathematical model was utilized. Several natural and artificial building materials were selected and examined (stones, clay bricks and natural hydraulic lime based mortars).The proposed mathematical model was found to fit successfully experimental drying kinetics data. Moreover, this model incorporated the environmental conditions, as well as the materials characteristics on the drying process. Thus, it can be applicable for use in building simulators concerning moisture transfer phenomena in building physics.

Unraveling the droplet drying characteristics of crystallization‐prone mannitol – experiments and modeling

Spray‐dried mannitol is a potential lactose replacement in pharmaceutical formulations, yet the drying behavior of individual mannitol droplets within the spray chamber has not been fully understood. This work explored the drying characteristics of mannitol by employing the reaction engineering approach (REA) in data analysis. A glass filament single droplet drying technique was used to monitor the changes in droplet temperature, mass, and diameter. The drying kinetics data obtained clearly demonstrated the droplet “wet‐bulb” period, the crust formation, and the crystallization phenomena. The master activation‐energy curves developed from REA modeling responded sensitively to varying drying temperatures, which could have led to different crystallization events. The deviation of these plots from the expected norms that do not encounter a phase change was used effectively to discern the physics involved. A REA kinetic model was proposed to assist in process optimization of large‐scale spray‐drying operations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1839–1852, 2017

Modelling the Thin-Layer Drying Kinetics of Untreated and Blanch-Osmotic Pre-treated Tomato Slices

The objective of this study was to investigate the effect of pre-treatment and drying temperature on the drying kinetics and nutritional quality of tomato (Lycopersicon esculantum L.) under hot air drying. Tomato samples were blanched at 80oC and osmotically dehydrated using 20% w/w sodium chloride solutions at 30oC for 20 min. The blanch-osmotic pre-treated and untreated tomato slices were dried at temperature of 40, 50, 60, 70 and 80oC, respectively in a hot air-dryer. The results showed that blanch-osmotic pre-treatment offered a higher drying rate and lower or faster drying time than untreated condition. The tomato drying regime was characteristically in the constant and falling rate period. The tomato drying rate curve showed characteristics of porous hygroscopic solids. The optimum drying temperature for tomato was found to be 60oC. Four semi-empirical drying models of Newton, Page, Henderson and Pabis, and Logarithmic were fitted to the drying data using non-linear regression analysis. The most appropriate model was selected using the coefficient of determination (R2) and root mean square error (RMSE). The Page model has shown a better fit to the drying kinetics data of tomato in comparison with other tested models. Transport of moisture during drying was described by Fick’s diffusion model application and the effective moisture diffusivity (Deff) thus estimated. The Deff at 60oC was 4.43 × 10-11m2/s and 6.33 × 10-11m2/s for blanch-osmotic pre-treated and untreated tomato slices, respectively.

Conversion/degradation of isoflavones and color alterations during the drying of okara

The aim of this work was to investigate the convective drying of okara, a by-product from soymilk processing. The specific objectives were as follows: to model the drying kinetics using the Fick and Page models; and to evaluate the color and isoflavone content during drying. An oven-dryer with hot air circulation at 50, 60 and 70 °C was used. Samples were taken at each predetermined time to analyze the isoflavone profile by UHPLC and the color. The Page model fitted the drying kinetics data well. Throughout drying, there was a decrease in the color parameters (lightness and hue angle), showing sample browning. A significant reduction in the isoflavone content was observed at 70 °C, possibly due to thermal degradation. During the initial stage of drying at 50 °C, daidzin and genistin were converted to the aglycones daidzein and genistein, respectively, probably due to residual β-glucosidase activity. However, isoflavone degradation was observed during the final stages of drying at 50 °C.