This study investigates the effectiveness of microwave-assisted hot air drying (MAHD) on corn drying process, water migration, dielectric properties, microstructure, and quality attributes. The ...research compares MAHD with conventional hot air drying (HAD), employing various microwave powers (1.2–3.6 kW) and hot air temperatures (35–55 °C). The results demonstrate that MAHD significantly reduces the drying time (by 30.95–64.29%) compared to HAD. Two-term model accurately describes the drying kinetics of corn. Microwave facilitated the transformation and more uniform distribution of water within the corn, observed through LF-NMR/MRI. Additionally, MAHD was effective in preserving the color and carotenoids, while reducing fat acidity, indicating better quality retention. Microstructure analysis revealed that MAHD increases microporosity and cracks in corn, which correlates with the observed enhancement in drying efficiency. These findings underscore the potential of MAHD as a superior method for drying corn, offering benefits in terms of reduced drying time and improved quality preservation.
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•MAHD significantly reduces corn drying time and improves drying efficiency.•LF-NMR/MRI shows improved water migration and uniform distribution in corn treated with MAHD.•The Two-term model accurately describes corn drying kinetics under MAHD conditions.•MAHD effectively preserves the quality of corn, maintaining color and carotenoids.
This study provides a comprehensive analysis of the vacuum drying process for sludge drying, with a focus on optimizing energy efficiency and emission control. The study used both lab-scale static ...and pilot-scale vacuum drying systems to test various parameters like vacuum levels, heat source temperatures, and sludge thicknesses. The results indicated that optimal drying conditions were achieved at a vacuum level of −0.06 MPa, a heat temperature of 140 °C, and a sludge thickness of 3.4 mm, where the drying rate reaches 0.13278 g·g−1·min−1. The study underscores the significant influence of vacuum level, temperature, and sludge thickness on drying rates. The Page model was used to analyze drying kinetics, elucidating how changes in these parameters affect drying characteristics. Furthermore, the study also examined the pollutant emissions and energy efficiency at the pilot scale. It found that high vacuum environments could efficiently dry sludge using low-temperature heat source, leading to average energy consumption per unit evaporation of 3020.29 kJ/kg, which is lower compared to traditional methods. By harnessing low-grade industrial waste heat, this can be further reduced to 875.76 kJ/kg. This study offers valuable insights for sustainable sludge management systems, highlighting the environmental and economic benefits of vacuum drying technology. The detailed experimental approach and thorough analysis make a significant contribution to the field of the sludge drying.
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•Identified varying drying rates influenced by operational parameters•Demonstrated reduced energy consumption in vacuum drying•Highlighted the impact of operational conditions on moisture diffusivity in sludge•Provided insights into pollutant emissions variations during the vacuum drying
The difficulty of measuring the drying rate of biomass under hot air convection conditions due to the influence of multiple factors, such as environmental conditions and material properties; and the ...problems associated with the variability of desiccation curves under changing conditions makes the use of mass transfer models based on diffusion and convection generally quite inaccurate. The research proposes the use of neural networks to determine the average drying speed (g removed water in unit of biomass material (kg) in unit time (s)), highlighting its ability to handle complex and variable data, as well as its adaptability and robustness. After 62 iterations, the R2 of the training process reached values of 0.93. Subsequent validation provided an R2 of 0.88. The mean square error was less than 10−3 g dryed water kg−1 biomass s−1. Traditional mass transfer models applied to drying processes were compared with experimental data. It has been proven that the values of the convection coefficient in mass transfer are overestimated when obtained from the Sherwood number. Values of this coefficient applied to wood are 30 times lower due to capillary phenomena and electrostatic forces between the material and the water particles.
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•Neural networks achieved measuring the drying rate of biomass under hot air convection conditions.•After 62 iterations, the R2 of the training process reached values of 0.93.•Traditional mass transfer models applied to drying processes were compared with experimental data.•Overestimation of convection coefficients in mass transfer when derived solely from Sherwood number.
Basil (Ocimum sanctum) leaves, commonly known as holy basil, have various health benefits due to their rich phytochemical content. However, fresh basil leaves face challenges related to their ...perishability and short shelf life. This study explores the use of edible coating, specifically chitosan, to extend the shelf life of basil leaves. Then basil leaves with chitosan coating were dried using microwave-assisted drying (MAD) method with variations of microwave power (136, 264, 440, and 616 W), mass of basil leaves (5, 10, and 15 g), and chitosan concentration (0, 2.5, and 5 %). The purpose of this study is to analyze the color, effective moisture diffusivity, and drying kinetics. Five mathematical models and seven error functions were used. The Avhad and Marchetti Model was identified as the most suitable model to describe the drying kinetics of basil leaves with chitosan coating. The Deff value increased with decreasing mass of basil leaves, decreasing chitosan concentration, and increasing microwave power. Deff values ranged from 0.001 to 0.002 m2/s. The thickness of the basil leaves also played a role in the fluctuation of Deff values. The highest ΔE value was obtained by 5 % concentration of chitosan. The chitosan coating, especially at a concentration of 2.5 %, showed discoloration indicating better preservation of the original color of basil leaves. In conclusion, this study shows that chitosan coating and MAD are effective strategies to extend the shelf life of basil leaves and can provide valuable insights for future applications in leaf drying or thin layer drying processes.
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•First study on drying basil leaves with chitosan coating using MAD•The Avhad and Marchetti model showed a good fit for drying chitosan-coated basil leaves.•At 2.5 % chitosan concentration showed better color change for preservation of basil leaves.•The Deff value increased with increasing MP and decreasing leaf mass and chitosan concentration.•The highest ΔE value was obtained by 5 % concentration of chitosan.
Cold filamentary microplasma (CFM) pretreatment combined with infrared (IR)dryer was implemented, and its effect on drying efficiency (i.e., (drying) kinetics and moisture diffusivity) and quality ...attributes (i.e., total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (AOA), ferric reducing antioxidant power (FRAP), color, and FT-IR spectra) of apple slices (5, 7, and 10 mm thicknesses) were examined. Results showed the electrically induced channels in the CFM-pretreated samples appeared as a tree-like structure. Besides the drying time decreases of 18.0%, 13.0%, and 10.5% that respectively occurred at CFM-pretreated IR-dried apple slices thicknesses 5, 7, and 10 mm, the browning therein appeared as the main visual effect with reduced total specific energy consumption. CFM-pretreatment enhanced the dried apple slices’ quality via increasing TPC, TFC, and AOA respectively ranging 2.5–14.3%, 19.1–25.9%, and 8.3–35.4%. Additionally, the detected chemical compounds corroborated the FT-IR spectral peaks.
•Cold filamentary microplasma (CFM) pretreatment and infrared (IR) drying were combined.•Drying efficiency and quality attributes of CFM pre-treated IR dried apple slices were investigated.•CFM pre-treated IR drying appear more effective on thin apple tissue thicknesses.•CFM pre-treated IR drying is promising to sustain the apple slice quality.
The drying of fruits and vegetables is a complex operation that demands much energy and time. In practice, the drying of fruits and vegetables increases product shelf‐life and reduces the bulk and ...weight of the product, thus simplifying transport. Occasionally, drying may lead to a great decrease in the volume of the product, leading to a decrease in storage space requirements. Studies have shown that dependence purely on experimental drying practices, without mathematical considerations of the drying kinetics, can significantly affect the efficiency of dryers, increase the cost of production, and reduce the quality of the dried product. Thus, the use of mathematical models in estimating the drying kinetics, the behavior, and the energy needed in the drying of agricultural and food products becomes indispensable. This paper presents a comprehensive review of modeling thin‐layer drying of fruits and vegetables with particular focus on thin‐layer theories, models, and applications since the year 2005. The thin‐layer drying behavior of fruits and vegetables is also highlighted. The most frequently used of the newly developed mathematical models for thin‐layer drying of fruits and vegetables in the last 10 years are shown. Subsequently, the equations and various conditions used in the estimation of the effective moisture diffusivity, shrinkage effects, and minimum energy requirement are displayed. The authors hope that this review will be of use for future research in terms of modeling, analysis, design, and the optimization of the drying process of fruits and vegetables.
The aim of this study was to evaluate the inulin prebiotic content in extracts obtained from the leaves and tubers of Crem (Tropaeolum pentaphyllum) collected before, during, and after flowering. In ...vitro-cultured Crem seedlings were also assessed. Extractions were performed by boiling in hot water (80 ± 2 °C) for 1, 2, and 4 h. The pre-extraction drying curve indicated that 18 h at 55 °C are sufficient for the dehydration of leaves, sliced tubers, and seedlings. All models (Lewis, Henderson-Pabis, Page, and Logarithmic) used for prediction in drying kinetics showed good fit quality parameters: coefficient of correlation (R2) (>0.9959) and root mean square error (RMSE) (<0.0180). The results revealed variations in inulin levels depending on the developmental stage, extraction time, and plant parts. We observed that seedlings had the lowest inulin levels after 4 h of extraction, with a maximum of 11.4 mg/g. In leaves collected after the flowering period, the highest levels were found, with a peak concentration of 15.03 mg/g after 2 h of extraction. Inulin levels in tubers were 5 and 7 times higher than those found in above-ground and in vitro-cultured material, respectively, reaching a value of 70.92 mg/g of inulin in the extracts of samples collected during the flowering period after 2 h of extraction.
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•Crem (Tropaeolum pentaphyllum) extracts contain inulin.•Inulin levels depend on the stage of development, extraction time, and parts of the plant.•Inulin can be applied as a prebiotic.
•The exergy efficiency of the drying chamber ranged from 16.44 % to 70.47 %.•The overall efficiency of the greenhouse and the solar air collector were calculated to be 42 percent and 62 percent, ...respectively.•an energy and exergy balance of the forced convection solar drying system has been presented.•the payback period for the system was estimated to be 1.82 years.
Solar drying is a thermodynamic method of controlling moisture content that uses a non-depletable free renewable energy source. This work discussed a qualitative and economic analysis of a forced convection drying system for tomato slices in an agricultural greenhouse under Tunisian climatic conditions. Then an exergy and energy balances of the drying system were presented. The tomato’s thin layer was dried in a mixed convection solar drier for 79 h and 127 h in a conventional sun drying process from an initial moisture content of 20.27 to 0.36 kg H2O per kg of dry matter. Energy and exergy analyses of the tomato’s drying process were investigated. It was also discovered that the exergy efficiency of the drying chamber ranged from 16.44 percent to 70.47 percent. The overall efficiency of the greenhouse and the solar air collector were calculated to be 42 percent and 62 percent, respectively. To determine the quality of fresh and dried tomatoes, color analysis was performed. A cost-benefit analysis was performed, and the payback period for the system was estimated to be 1.82 years.
•The medium scale greenhouse solar dryer allows local industries to dry handmade papers at a faster rate.•Energy and economic analyses have been carried out to ascertain the feasibility of the ...proposed system.•Drying behavior of handmade papers has been evaluated with the help of ten mathematical models.•The developed GHSD's experimental results are promising and scaled up version of such system can be installed in industries.
In the presented experimental study, a medium-sized industrial greenhouse solar dryer (MSGSD) of floor area 1.82 x 1.52 m2 was developed using low-cost, locally available materials and tested in the winter season (November- December 2022) for eco-friendly handmade paper drying. The handmade papers having initial moisture content of 60 % (w.b.) were dried to a moisture content of 8–10 % (w.b.), and time taken to dry these papers varied from 3 to 8.5 h depending upon the paper type (off-white or coloured), paper thickness (100–200 GSM) and number of papers (75–150) dried inside the dryer. However, drying in the open sun and shade took 4 to 10 h and 19 to 29 h, respectively, to achieve a moisture content of 8–10 % (w. b.). The instantaneous thermal loss efficiency factor of the developed dryer was calculated for forced and natural convection modes of operation and found to be in the range of 13.1 % − 23.5 %. Ten theoretical models were investigated for characterizing the drying process, out of which the Midilli-Kucuk model was observed to be the best fit with experimental data. The economic analysis revealed a payback period of 0.61 years.
One crucial step in the propellant-making process that takes a lot of time and energy is drying. The study of inert propellants' vacuum drying behaviours – which mimics those of real propellants – is ...the main focus of this work. This study presents the development of analytical and numerical models for the vacuum drying of inert pro-pellants, which were validated through an in-house vacuum drying experiment. The calculation of effective diffusivity, a crucial parameter characterising the rate of solvent vapour transfer during the vacuum drying of inert propellant samples, is one of the outcomes of this work. It involves removing liquid solvents from the texture of a propellant. Conclusions and suggestions for technical practice are developed based on the studyʼs findings.
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