Moisture Removal Research Articles

A Study on Drying Characteristics, Color, and Vitamin C Preservation of Green Banana Slices Using a Vacuum Heat Pump System

Abstract This study aimed to evaluate the characteristics related to the removal of moisture from green banana slices and the effect of the drying conditions on color and vitamin C preservation using a drying system based upon the use of a vacuum heat pump. The green banana slices underwent drying at 40, 50, and 60°C with vacuum pressure levels of 0, 40, and 80 kPa. The average drying time decreased by 18.9% and 32.7% as the vacuum pressure and temperature increased, respectively. Six thin-layer models underwent assessment to explain the kinetic process involved in moisture removal using the vacuum heat pump set to provide differing experimental circumstances, and fitted to experimental data. Results showed that the characteristics of moisture removal from the green banana slices could most appropriately be explained by the Page model. There is in increase in effective moisture diffusivity, which ranged from 1.1658×10−10 to 1.9717×10−10 m2·s−1, with increases in temperature and vacuum pressure. Energy of activation ranged from 15.99 to 19.73 kJ·mol−1, which was explained by an exponential expression based on the Arrhenius models. The drying temperature of 50°C under a vacuum pressure of 80 kPa could preserve the vitamin C content by a maximum of 55.9%, which is the optimal drying condition for obtaining good product quality.

Моделирование процессов тепловой обработки головоногих моллюсков

The dehydration processes kinetics laws of squid and octopus, as a separate capillary-porous colloidal bodies group, were studied using industrial methods of energy supply. The research included an analysis of the influence of the species and size-mass composition of the material as well as operating conditions in the process of removing moisture from the product. The method was used to find critical points corresponding to a certain level of humidity in a specific period of time. It was found that cephalopods constant rate moisture removal is significantly longer compared to fish raw materials. For fish, the first critical point is reached at the end of a period of constant dehydration rate; for cephalopods, there is only one critical point during the entire moisture removal process. A mathematical model is proposed for finding critical humidity in the process of dehydration of cephalopods. The authors of the study developed similarity numbers in order to reduce the set of dehydration curves of cephalopods of different composition and geometric sizes under conditions of various methods and rigidity of heat treatment into one generalized dependence. The obtained patterns provide some ways to design and optimize heat and mass transfer processes and devices in food engineering.

Development of a new type of polymer for modification natural fibers

The paper presents data on the use of developed water-soluble compositions in combination with glycerin for modifying natural fibers. The study of the properties and use of polymers as a regulator of textile fibers was laid down in the scientific foundations of this work. The study of the physicochemical properties of water-soluble compositions has substantiated that compositions based on water-soluble polymers meet the requirements for their use in the process of epilamination of natural fibers. The presence of various polyfunctional groups in the structure of a water-soluble polymer allows them to perform the functions of a modifier, forming a thin film on the surface of natural fibers that prevents the removal of moisture, reduces fiber breakage and enhances physical and mechanical properties. This made it possible to establish that epilamination not only preserves the fiber from damage when interacting with the working parts of technological machines, but also improves the processability of the fiber.

Experimental and computer study of the mechanism and identification of conditions for energy-efficient removal of moisture from materials under ultrasonic exposure.

The article is devoted to investigation of energy-efficient moisture removal from capillary-porous materials. Moisture is removed by dispersion at collapse of cylindrical cavitation bubbles, formed by ultrasonic vibrations in the capillaries of the material. Mathematical model, which allowed to investigate the mechanism of moisture dispersion, has been developed. Necessity of realization of cavitation bubble full life cycle in capillary (slow growth, rapid expansion with deformation, collapse) was found. An optimal range of sound pressure levels from 150 dB ("critical level" at which dispersion of water from capillary starts) up to 170 dB (dispersion productivity growth stops due to cavitation bubbles reaching maximum size equal to diameter of capillary) was determined. It is shown that the size of the dewatered sample for maximum drying efficiency should correspond to the ultrasonic wavelength in air. Ultrasonic dispersion of liquid during drying was confirmed experimentally. It is found that for significant reduction of drying time (up to 50% and more) it is necessary to affect in the range of 165-170 dB. And the materials to be dried must be placed as particles or layers having dimensions or thicknesses corresponding to the length of the ultrasonic wave in air. The implementation of ultrasonic drying, on the example of food products (beets) provided a reduction in drying time of 1.9 times, while reducing energy costs by 1.7 times in comparison with convective drying.

Evaluation of structural performance of thinasphalt pavement reinforced with wicking geotextiles over expansive soils

This research provides a comprehensive evaluation of the effects of a wicking geotextile capable of multiple functions, including separation and reinforcement and gravity and capillary suction-induced drainage for subsurface layers in flexible pavements built over expansive soils. Two test sections were designed and constructed near central Texas, which were prone to distress from cyclic moisture-induced strains related to expansive soils, during the Fall of 2018. The base layers in the first and second sections were constructed with reclaimed asphalt pavement and crushed stone aggregate, respectively, and wicking geotextiles were installed between the base and subgrade layers. The adjacent lane to the test sections was selected as the control section. Falling weight deflectometer (FWD) testing was conducted to evaluate the in-situ moduli of the pavement layers. Multiple performance indicators were selected to compare the performance of reinforced and control sections. A performance prediction software program was used to investigate the performance of the sections according to the mechanistic-empirical design and analysis approach. The results showed the rapid removal of moisture has a significant impact on controlling the permanent deformation of the pavement layer. FWD results revealed that the reinforced layer helped to improve the base and subgrade moduli values. The performance prediction results showed the wicking geotextile has the potential to be used for reinforcing the pavements constructed over expansive soil

ВЛИЯНИЕ ПОРОШКООБРАЗНЫХ ОКСИДНЫХ ДОБАВОК НА СИНТЕЗ ОКСИДА ЖЕЛЕЗА (III)

Nanocomposites are widely used in many fields of science due to their impressive physical and chemical characteristics. Despite the fact that this class of composite materials has appeared relatively recently, there are a considerable number of methods for their production. When designing such materials, a special role should be given to nanocomponents and their production. This work examines the possibility of synthesizing nanosized iron (III) oxide and its mixtures with silicon dioxide and aluminum oxide in solutions of iron (III) nitrate with glycine, which can be used as a component of composite dispersion-strengthened materials. The synthesis of iron (III) oxide and its mixture with aluminum oxide and dioxide was carried out in the self-propagation mode for the system in the solid state. The solid state of the mixture corresponds to the residual amount of bound water - two moles per mole of Fe(NO₃)₃. When studying the process of preparation for synthesis, it was shown that the introduction of additives does not have a significant effect on the residual moisture content, but helps to reduce the combustion temperature by 22-175 ° C and intensify the moisture removal process, i.e. the time for producing a solid solution is reduced by 31-56%. The mixture used Fe(NO₃)₃ ·9 H₂O (75%) + NH₂-CH₂-COOH (25%) as a result of synthesis by combustion makes it possible to obtain Fe₂O₃ with Ssp = 12 m2/g. The introduction of additives makes it possible to increase the efficiency of synthesis in the self-propagation mode and increases the specific surface area, but in the case of SiO2, Al₂O₃ it leads to contamination of the product with these components. It was found that the introduction of oxides into the composition allows one to regulate the surface area of the reaction products over a wide range. Input of 5% SiO2 allows you to achieve Ssp = 30-32 m2/g, iron (III) oxide and aluminum oxide leads to an increase in specific surface area to 20-25 m2/g.

The methods of optimization and regulation of the convective drying process of materials in drying installations

In this work, based on fundamental principles well-established in the field of drying technology, optimization for the process of material drying involves controlling the mechanism of moisture transfer by influencing diffusion and thermo-diffusion processes. Based on the Kirpichov criterion, a quantitative measure of moisture transfer dynamics is ensured, while Nusselt numbers help control temperature gradient and efficient moisture removal. The article proposes the use of empirical relationships between Nusselt numbers and problem parameters such as moisture content, temperature, and airflow velocity. Optimizing drying parameters based on the proposed equations can contribute to improving drying quality, reducing process time, and lowering energy consumption. The proposed methods of moisture and temperature gradient control within the material are sustainable and allow us to achieve uniform drying without causing excessive stresses or deformation.

Comparative study of mathematical and experimental models of coffee bean drying rate in a solar dryer simulator

The drying process of coffee beans requires heat energy to evaporate the moisture content in the material to be dried. Arabica coffee is dried at controlled temperatures (50°C, 60°C and 70°C) and wind speeds (0.4 m/s, 0.8 m/s and 1 m/s). The initial moisture content of the coffee bean test of 70% was dried to a moisture content of 11%. The drying air temperature is important for drying at high temperatures using a solar dryer simulator, which results in rapid moisture removal and reduced drying time. Drying was carried out to obtain the rate of reduction of moisture content experimentally compared to theoretically on mathematical models of drying agricultural products (Newton, Modified Henderson and Pabis and Modified Midili). Drying parameters are related to mass loss, temperature and humidity. From the results of the calculation of the experimental water content reduction rate with 3 formulas, the closest equation is Modified Midili.

Drying kinetics and quality attributes analysis of moringa (Moringa oleifera) leaves under distinct drying methods

AbstractThe present work aimed to analyze the drying kinetics and color degradation of moringa leaves in selected drying methods. Also, quantitatively analyze the retention of phytochemicals and antioxidant capacity. Moringa leaves were dried using three methods, namely, freeze‐drying (−42 ± 2°C, 0.024 ± 0.001 mbar), microwave drying (200, 400, and 600 W), and hot air oven drying (55, 65, and 75°C). Drying kinetics revealed that the drying of moringa leaves occurred in the falling rate period, which means the diffusion process controlled the moisture removal from leaves. The color degradation was most minor in freeze‐dried leaves, followed by microwave‐dried leaves at 200 W. The value of total phenolic content was found maximum (57.42 ± 2.49 mg GAE/g dm) under microwave drying at 200 W, while the same was found least in quantity (24.62 ± 1.10 mg GAE/g dm) for samples dried under hot air oven drying at 65°C. A similar pattern was observed for total flavonoid content. The antioxidant capacity of the samples dried in the freeze dryer was highest at 5.94 ± 0.25 mg GAE/g dm. This research revealed that microwave drying at 200 W is best regarding the overall quality attributes of moringa leaves.Practical ApplicationsDrying is one of the essential processes in the food industry, for example, drying is crucial for the production of herbal medicines, nutritional supplements and extracts, leaf‐based culinary ingredients, aroma and essential oils, natural dyes and pigments, etc. It is used to increase the shelf‐life of agricultural produce; it facilitates the transportation and storage of food products. This paper may help in the selection of the drying method and condition for leaves drying to have desired characteristics in the final product like color, bioactive compounds, or antioxidant properties; May help in the trade‐off among quality, time, and cost of the production. Moreover, it may be helpful in the designing of the multi‐mode dryer which may produce superior quality products with great energy efficiency in less time. Which further facilitates the manufacturing of nutritionally rich food products.

Development of rotary dehumidifier with silica-gel-based composite desiccant

The desiccant dehumidification system's key component, the desiccant wheel, can perform effectively using composite desiccant materials. Evaluation of the desiccant wheel's performance using composite desiccant material is the primary goal of this study. Authors have compared the performance of two desiccant wheels; one is packed with traditional Silica-gel, and the other is a composite of Silica-gel and calcium chloride in a ratio of 3:2 by weight. A rotary wheel is developed with rectangular channels parallel to the wheel's axis. The novelty of this research lies in the improved design of the desiccant wheel. Unlike other techniques involving pressure losses and ineffective space utilization, this design offers better space utilization and fewer pressure losses. In addition, wheel fabrication is less costly and easily reusable with other desiccants. Three performance indicators were evaluated through experimentation: dehumidification capability, moisture removal capacity, and dehumidification coefficient of performance. Results show that the Parallel channel desiccant wheel achieves 25% higher dehumidification capability and 55% greater moisture removal capacity. The specific humidity of the air is reduced by 35% using the composite desiccant wheel. Comparing the composite desiccant to traditional Silica-gel, its dehumidification coefficient of performance is 40% higher.

CERCETĂRI PRELIMINARE PRIVIND REALIZAREA UNUI MATERIAL COMPOZIT, BAZAT PE MATRICE DE NĂMOL ȘI DEȘEURI AGRICOLE, CA MATERIALE DE UMPLUTURĂ

The article presents the results of preliminary experiments necessary for the foundation of an experimental method that ensures the design and manufacturing technology for a category of composite materials with a mud matrix and agricultural waste insertion. The resources and physico-chemical properties of the mud matrix as well as the resources and physical properties of potential agricultural waste constituents of the insertion in the composite material are presented. The technological variant for the manufacture of the finished product is also presented, consisting of a compression system of the composite mixture in a paste state until solidification with moisture removal (dehydration). From a large number of parameters characterizing the experimental system, few have been varied (insertion concentration in the material, height of the raw material column in the press, raw material density, pressing force), while the quality parameters of the process have only been considered for the capacity of dehydration and material densification. The statistical analysis of the results shows that for the capacity of dehydration and densification, the main input parameters that influence are the initial moisture and initial volume of raw material. Results are obtained that allow the development of a mathematical model for the technological process of manufacturing the composite material. The purpose of the research described in this article is to determine the feasibility and feasibility conditions of the material in its possible variations. This means identifying the insertion concentration and moisture intervals of the material before extrusion, possible. The upper and lower limits of these parameters are sought, so that the material exiting the die does not immediately, or over time, disintegrate, and at the same time, the extrusion process is possible with a reasonable energy consumption.

Quality evaluation of house cricket flour processed by electrohydrodynamic drying and pulsed electric fields treatment

House crickets are expected to play a significant role in the future food sector. Electrohydrodynamic (EHD) drying offers an environmentally friendly alternative to conventional drying methods. Pulsed electric fields (PEF) is a non-thermal process that facilitates conventional processes. EHD was applied to house crickets with and without PEF pretreatment, and the effect of PEF and EHD on the quality of the insects was evaluated. PEF pretreatment positively affected the oven drying at 60 °C by reducing its duration and thus decreasing the energy consumption by 14.22%. Moisture removal of EHD was not sufficient to replace oven drying, but when combined with oven drying, the overall energy consumption was reduced by >50%. PEF processing also increased the protein solubility (53.07% higher than the respective control) and antioxidant activity (24.05% higher than the respective control) of the oven-dried samples and reduced the histamine content of the EHD-dried samples (25.87% lower than the respective control).

Fluidization‐bed drying and microwave radiation effects on drying rate, fatty acid, protein, and germination of flaxseed

AbstractFlaxseeds are known for their invaluable omega‐3 fatty acids and proteins. Flaxseeds need to be dried to 10%w.b. moisture for safe long‐term storability. Traditional drying ruptures the nutritional properties, therefore, this study analyzed the effect of fluidized‐bed and microwave drying on the fatty acid and protein constituency of flaxseed. The drying air temperatures in the fluidized‐bed drying tests were 40, 50 and 60°C. Three microwave power densities were selected 0.3, 0.6 and 1 W g−1. Results showed a minor effect on fatty acids whereas a significant effect on protein content with both the drying methods. A protein reduction of 7, 21, and 23% was observed for drying air temperatures of 40, 50, and 60°C, respectively. For the microwave tests, 39, 58, and 63% protein reductions for 0.3, 0.6 and 1 W g−1 power densities were observed, respectively. The fatty acids showed a maximum increase of 0.85% for fluidized bed drying and 1.23% for microwave.Practical applicationsThis study contributes a step‐forward knowledge toward adoption of microwave technology in flaxseed oil extraction industry. Previous pilot‐scale studies solely on microwave utilization have shown limited scale‐up due to its high infrastructure cost associated with emitting high‐power densities. However, if explored with a combination approach along with fluidized bed (40°C at 0.3 W g−1) to assist in early removal of surface moisture from flaxseed, it could be a potential platform to increase the productivity in parallel to matching the associated overall cost. A proper cost analysis could be a future aspect of this study.

Modeling and multi-objective optimization of polymer desiccant cooling system

The polymer desiccant cooling system (PDCS) efficiently reduces energy consumption compared to the vapor compression system (VCS). In this paper, a PDCS integrated heat pump is proposed. Experimental and simulation are used to analyze the performance of the PDCS. The control strategy is optimized with the NSGA Ⅱ algorithm. A case study in Shanghai illustrates the practical application of the PDCS optimization strategy. The calculation results based on the thermal comfort requirement show the maximum energy consumption of optimized PDCS, routine PDCS, and VCS are 549.9 kW, 597.7 kW, and 1327.7 kW. About 62.7 % and 72.3 % of energy can be saved in routine PDCS and optimized PDCS compared to VCS. Moreover, the maximum moisture removal efficiency of the above scenarios is 10.67 kW/(g·s), 11.56 kW/(g·s), and 25.42 kW/(g·s), separately. Additionally, the maximum coefficient of performance is 0.530, 0.457, and 0.182, respectively.

Investigation of the moisture classification and moisture removal behavior of diamond wire saw silicon powder waste cake

When processing silicon wafers for photovoltaic power generation, approximately 35 % of high-purity silicon is lost as a diamond wire saw silicon powder (DWSSP) waste cake with a high moisture content. The high moisture content of DWSSP results in the oxidation of high-purity silicon, which hinders the recovery and utilization of silicon resources. Disappointingly, a method for the removal of moisture from the DWSSP waste cake, which is crucial for silicon recovery, has not yet been revealed. In the present study, a novel investigation was conducted to determine the moisture classification of a DWSSP waste cake and to reveal the moisture removal behavior. The results indicate that the moisture content in the DWSSP waste cake can be divided into two distinct categories: surface adsorbed water and capillary water. Moreover, the kinetics analysis and simulation demonstrated that the elimination of moisture predominantly takes place during the constant-rate period and the falling-rate period. Increasing the drying temperature and reducing the equivalent diameter of the DWSSP waste cake will contribute to improving the efficiency of moisture removal. The application of the findings of this study can help to reduce the harmful environmental impacts of DWSSP and achieve the efficient recovery of silicon resources.

A state-of-art review of dew point evaporative cooling technology and integrated applications

Energy consumption of air conditioning accounts for a large proportion of energy consumption of buildings, and it is indispensable to reduce the operational cost of air conditioning. Indirect evaporative cooling (IEC), especially dew point evaporative cooling (DPEC) technology, which takes away heat through water evaporation for cooling, becomes an effective technology to improve energy efficiency. In this review, the indirect DPEC technology is introduced and the current research states are summarized in detail. The improvements of performance and model analysis of DPEC are investigated by numerical simulations, experimental works and machine learnings, which are elaborately described respectively. DPEC can reduce the air temperature to the dew point to achieve higher cooling effectiveness than the conventional IEC. The impacts of the design, intake conditions, geometry and water distribution, membrane materials on the performances of DPEC heat exchanger are also explored, including the wet and dry-bulb efficiencies, cooling capacity, coefficient of performance and other parameters to evaluate the performances. Based on the experimental researches, the mathematical models with different theories such as finite volume method, enthalpy method, and other methods are built, which are based on Energyplus, Matlab, Fluent and other tools. DPEC is suitable for hot and dry regions. The applications of DPEC in hot and humid region are extended by integrated with dehumidifier to meet requirements of moisture removal. The optimal analyses of machine learning for the combination mode of DPEC and hybrid system are described subsequently. Finally, the future research directions and application occasions of DPEC are proposed.

Kinetics and thermodynamic parameters of palm empty fruit bunch pyrolysis promoted by calcium-rich wastes from coastal-marine residue

Kinetics and thermodynamics of palm empty fruit bunch (PEFB) pyrolysis have been determined in the presence of catalyst from clam shell (Anadara sp.) (CS) using thermogravimetric analysis. PEFB pyrolysis occurred in three stages (moisture and volatile removal, cellulose and hemicellulose, and lignin decomposition), with maximum degradation occurring at 200–400 °C. Activation energy calculated using the iso-conversional method varied from 89.80 to 169.63 kJ/mol for Friedman, 66.25–119.79 kJ/mol for FWO, 53.33–96.44 kJ/mol for KAS, and 50.90–92.04 kJ/mol for Starink. Pre-exponential factor values ranged from 104–1017 and 104–1014 s−1 for non-catalytic and catalytic pyrolysis. The thermodynamic parameters values varied from 47.28 to 99.44 kJ/mol for enthalpy, from 98.23 to 151.62 kJ/mol for Gibbs free energy, and from −0.0858 to −0.0808 kJ/mol for entropy. The reaction mechanism is dominantly second-order and complex. The analysis revealed that PEFB and CaO catalyst from CS are efficient biomass and effective catalyst for bioenergy production.

Convective drying of black rice grains (Oryza sativa L.): new mathematical modeling insights and thermodynamic properties

The aim of this study was to investigate the thin layer drying of brown rice grains at different temperatures (35-75 °C), exploring its kinetics and thermodynamic properties. Black rice grains (30% b.u.) were subjected to convective drying, and the experimental data were subjected to analysis of theoretical, semi-theoretical and empirical drying models, and thermodynamic parameters were calculated. Increasing temperature accelerated drying, shortening the time required to reach moisture balance. The modified Page model modified by Cavalcanti-Mata showed excellent fit to the experimental data, standing out for its simplicity and effectiveness in describing the relationship between water content and drying time. The analysis of thermodynamic properties revealed that the activation energy increased with temperature, evidencing its influence on moisture removal. The observed variations in thermodynamic properties reinforce the importance of considering energy factors in drying. The results offer insights to optimize the black rice grain drying process, contributing to advances in the food industry and providing a basis for future research in the processing of agricultural products.

Atmospheric water harvesting by osmotic distillation and direct contact membrane distillation using hydrophobic hollow fiber membranes

The use of a liquid desiccant air dehumidifier is an energy-efficient technology that can improve both indoor air temperature and humidity. However, the risk of concentrated liquid desiccant leakage into the air conditioning system during dehumidification can corrode the system, negatively impact indoor air quality, and potentially harm residents. To address this issue, this study investigates the effectiveness of osmotic distillation (OD) and direct contact membrane distillation (DCMD) for dehumidification and regeneration, respectively. The study analyzes the impact of inlet operating parameters, including liquid desiccant concentration, temperature, and flow rate, and air flow rate on the dehumidification performance and stability of the OD process. Calcium chloride was utilized as the liquid desiccant in this study. The results indicated that the dehumidification performance of the OD process improved with a higher desiccant concentration and lower desiccant temperature. However, the desiccant flow rate did not have a significant impact on dehumidification performance. Furthermore, the dehumidification performance decreased with a higher inlet air flow rate, but the moisture removal rate increased. The OD process demonstrated stable operation during the dehumidification process. DCMD was effective for desiccant regeneration, and no scaling occurred due to the deposition of calcium chloride crystals. However, the permeation flux of DCMD decreased as the feed concentration increased due to a decline in the feed vapour pressure and an increase in concentration polarization effect. In conclusion, the experimental results indicated that OD can effectively dehumidify humid air, while DCMD is a viable option for desiccant regeneration.

Enhanced moisture adsorption of activated carbon through surface modification

Activated carbons are widely used as adsorbents in industries for various applications. The mechanism of moisture interaction with the industrial adsorbents is complex and yet to be clearly elucidated. The adsorption mechanism heavily depends on several parameters that include the pore size and distribution, surface chemistry, and treatment conditions. Various surface functional groups on the carbonaceous materials play a significant role in water adsorption, mainly the oxygen-containing functional groups (OFGs). A commercial mesoporous steam-activated carbon was subjected to surface modification on treatment with strong oxidizing agents and subjected to the adsorption of moisture. The isotherms were generated covering a temperature range of 30–50 °C. The adsorption capacity was observed to significantly improve post-treatment with oxidizing agents, while the effect was observed to be profound at lower partial pressures. A sharp increase in the moisture uptake indicates that the oxidized carbons have a higher affinity to moisture even at low concentrations and this could have a significant influence on the targeted molecules, since the moisture as a contaminant is expected to be present at low partial pressures. On the other hand, such a trend is highly favorable if carbon is to serve as a sorbent for the removal of moisture, as several-fold improvements in adsorption capacity were noticed as compared to virgin AC. Additionally, the adsorption capacity was also found to be significantly higher as compared to popular moisture adsorbents, such as silica gel and zeolites, especially at low partial pressures.