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Drying food products and materials is one of the most common methods in processing raw materials, yet it remains an energy-intensive process. The main drawback of traditional electric convective household dryers is the loss of heat and the wet waste drying agent into the environment. Furthermore, such units are characterized by uneven heating of the dried product, attributed to a temperature decrease and increasing humidity from bottom to top. (Research purpose) The purpose of this study is to conduct laboratory experiments on the drying process of apples focusing on evaluating the energy consumption required to evaporate 1 kilogram of moisture using a newly developed convective thermoelectric drying unit and compare its energy efficiency with mass-produced convective dryers. (Materials and methods) The findings from theoretical and experimental studies facilitated the development of a functional diagram and a laboratory prototype of a convective thermoelectric dryer using a thermoelectric heat pump. The drying process involves the utilization of a drying agent (heated air) with partial air recirculation, and heat recovery from the exhaust air. (Results and discussion) Temperature variations at designated control points and the relative humidity of the drying agent at both inlet and outlet of the developed unit were graphed and analyzed. The parameters of apples before and after drying in the thermoelectric drying unit are compared with those dried in a conventional household convective dryer. The study has resulted in developing an electrical control circuit for a thermoelectric drying unit and providing expressions to calculate the hot junction radiator of an air-to-air thermoelectric heat pump integrated into the developed drying unit. (Conclusions) The study estimated the average heat recovery by the cold junction radiator of a thermoelectric heat pump from the exhaust drying agent during the drying process, amounting to approximately 20 percent of the total energy consumption by the thermoelectric drying unit from the electrical grid. The research findings demonstrate that the laboratory prototype offers a more consistent drying process for the product. This is attributed to the incorporation of side air channels and a more efficient arrangement of the drying agent’s movement within the working chamber, as opposed to traditional convective dryers. These conclusions are substantiated by the test results. It is illustrated that the use of a developed thermoelectric heat pump with heat recovery from the waste drying agent can lead to a reduction in the installed power capacity of the drying agent heater and a decrease in the energy consumption for the drying process in the developed convective thermoelectric drying unit compared to mass-produced household convective dryers.

Green asparagus is widely consumed fresh due to its high nutritional value and a low calorie content. However, its short shelf-life due to a high water content causes high postharvest losses. In this study, we aimed to develop an innovative asparagus herbal drink to ease postharvest losses and diversify asparagus-derived products. We investigated the effects of process parameters on the quality of the herbal drink from green asparagus. In particular, we determined the optimal length and grinding size for asparagus and selected suitable blanching and drying methods. Analytical responses included the contents of total soluble solids, polyphenol, carbohydrates, and vitamin C, as well as the visual appearance of asparagus samples. The length of 5 mm was found suitable for subsequent steps as it facilitated an increase in solute in the asparagus infusion. Microwave blanching and convective drying were selected to achieve high contents of total soluble solids, polyphenol, carbohydrates, and vitamin C in the asparagus infusion. Dried asparagus ground into 1.5–2.0 mm particles was packaged into tea bags. The asparagus infusion subjected to sensory evaluation had a yellowish color, a characteristic asparagus flavor, and a relatively sweet taste. Total soluble solids in the infusion amounted to 26%. Our results showed a possibility of developing an asparagus herbal drink which could be a potent product in the commercial market. Therefore, further large-scale studies of the asparagus herbal drink should be carried out to enhance its feasibility in the food industry.

Post-harvest processing of the leaf mass of various agricultural crops has general patterns. The peculiarity of the structure of the leaves is that the amount of water contained in the leaf blade and in the midrib is approximately the same, but the area of the evaporating surface of the midrib is 10–15 times less than the area of the evaporating surface of the leaf plate. Therefore, the difference in drying modes for these parts of the leaves justifies the need for different physical methods of influencing them. The aim of the research was to substantiate experimentally the general principles of moisture removal from the leaf mass of various agricultural crops using microwave radiation. Processing in the microwave field was carried out for 1,0; 1,5; 2,0; 2,5 minutes. The treated leaf layers were dried naturally. Leaves dried by convection under natural and artificial conditions, only without microwave treatment, served as a control sample. For the post-harvest processing of plantain leaves, a combined drying method is recommended, where in the first phase the leaves are treated with microwave radiation for 2,0–2,5 minutes, depending on the thickness of the leaf layer, and then in the second phase under natural conditions for 8 hours. Microwave – processing followed by convective drying in natural conditions is considered the most compromise method for drying beet tops leaves both in terms of drying time and in terms of the energy intensity of the process. On the basis on the results of the research, the application of the most rational processes of post-harvest processing of leaf mass of agricultural crops was substantiated, which consists in their processing by microwave radiation, followed by convective drying in a natural way.

The work is devoted to the issue of the rational use of the solar energy in the technological process of fruit drying based on the use of solar drying devices, which are applied in various sections of the agro-industrial centers of Ukraine. The aim of this research was intensification of the fruits drying process using the solar energy by combining an air collector and drying chamber into a single power unit. To achieve the aim the heat exchange diagnostic techniques with alternative potentials of diffusion and moisture transfer was developed. This technique differs from those existing for the heat exchange research in that it allows the intensity of the moisture evaporation from a unit of the material surface to be calculated, based on the synthesis of the moisture content and the irreversible major laws of processes of the heat exchange characteristics of the fruits drying using the solar dryer. The above model makes it possible to diagnose the heat exchange processes and analyze the mathematical model of the heat exchange processes. It also allows modeling the changeable diffusion and moisture transfer potentials based on the dependences obtained and for the purpose of a further application in the methods and devices development to control the strain-deformed state of the fruits during the drying process. The method is offered for the calculation of diffusion and moisture transfer during drying fruits in the solar dryer.

The method of calculating convective drying of light industry thin materials based on the A. V. Lykov’s equation of drying kinetics and the B. S. Sazhin’s calculating method of drying is described. Processing of experimental data on wool felt drying, natural leather drying and fabrics drying is presented. Equations for determining the densities of heat flows, the intensity of moisture evaporation, the duration of drying process, and the temperature for the period of falling velocity are given. The values of the heat transfer coefficient and the Bio number for the second drying period are calculated. It was found that under mild drying conditions and insignificant temperature gradients along the thin body cross-section, the Bio number takes values less than one, and the main limiting factor for drying thin materials is the external heat and humidity exchange of the evaporation surface with the environment. It is shown that the relative drying speed is determined only by the moisture content of the material and does not depend on the drying mode. The comparison of the calculated parameters of drying according to the given formulas with the experimental values is given. The mismatch of values is in the acceptable accuracy zone of the experiment. Изложена методика расчета конвективной сушки тонких материалов легкой промышленности на основе уравнения кинетики сушки А. В. Лыкова и метода расчета сушки Б. С. Сажина. Приведена обработка экспериментальных данных по сушке шерстяного войлока, натуральной кожи и ткани. Даны уравнения для определения плотностей тепловых потоков, интенсивности испарения влаги, длительности сушки и температуры для периода падающей скорости. Вычислены значения коэффициента теплообмена и числа Био для второго периода сушки. Установлено, что при мягких режимах сушки и незначительных градиентах температуры по сечению тонкого тела число Био принимает значения меньше единицы, и основным лимитирующим фактором при сушке тонких материалов является внешний тепловлагообмен поверхности испарения с окружающей средой. Показано, что относительная скорость сушки определяется только влагосодержанием материала и не зависит от режима сушки. Дано сопоставление расчетных параметров сушки по приведенным формулам с опытными значениями. Несовпадение значений находится в допустимой зоне точности проведения эксперимента.

Drying of wood materials is one of the most important processes not only of wood processing, but also of many other industries. Drying processes involve the removal of moisture as a result of a phase transition from a liquid or solid to a gaseous state. This is due to the high energy intensity and duration of the process, especially for colloidal materials. The latter is due to the fact that with intensive drying the quality of the finished product often decreases, for example, when drying lumber cracks and warps occur, which is unacceptable in the manufacture of thermally modified products. In cases of thermochemical processing of dispersed materials, the quality of raw materials is determined only by the final moisture content of dispersed materials.Questions of heat and mass transfer during the drying of materials were carried out by Girsh M., Lykov A.V., Lurye M.V., Sazhin B.S., Dolinsky A.A., Golubev L.G., Rudobashta S.P., Shubin G.S., Romankov PG, Ginzburg A.S., Mikhailov N.V., Mushtayev VI. and etc. The paper deals with convective technology of dispersive materials. The zone of convective drying of dispersed materials is presented. Experimental and mathematical modeling of the drying process of wet dispersed materials before thermochemical processing was carried out. The results of theoretical and experimental studies of changes in temperature and humidity in the drying bin are presented. The nature of changes in temperature and humidity of dispersed particles in a drying bin was determined. The effective height of the layer in the counter-current dryer is determined by calculation, depending on the moisture content of the fuel and the temperature of the exhaust flue gases.

The article presents results of the study of convective drying of various types of natural leather using the theory of regular mode. The results of calculating the densities of heat fluxes and medium integral temperatures are discussed. Approximate equations are derived for calculating the drying kinetics in the period of the incident velocity. The possibility of applying the results of analytical solutions of the heat transfer equations in the calculations of drying kinetics is considered.

Various processing methods are used to bring grain to a steady state for storage, provide quantitative and qualitative grain characteristics, the most effective of which is grain drying. The results of experimental studies of vibration drying and industrial equipment operation experience showed the following benefits of using vibrations in drying dispersed materials: intensive mixing of material particles, intensive moisture removal due to constant renewal of moisture exchange surface, material temperature equalization in the bulk of drying apparatus, drying quality improvement, decrease in the vibro-pseudo-liquefaction startup speed, energy costs reduction, possibility of combining various manufacturing operations at continuous process running (transportation and drying, granulation and drying, shell formation and drying, fractionation and drying, etc.), creation of new highlyefficient vibration dryers with adjustable vibration settings. Having analyzed some types of vibration dryers it was decided to develop the design solution of the dryer for granulated and granular materials with high and controllable heat-mass transfer intensity. The proposed design solution allows simultaneously implement two controlled drying processes for heat-mass transfer intensification during drying bulk materials. There is intense moisture evaporation from the upper layers of granulated and granular materials due to the imposition of a temperature gradient on the controlled vibration mixing and motion (realized by bulk material displacement) along the section of U-like body in the first section of U-like vibration machine body. The moisture, remained in the central layers of granulated and granular materials in the second section of U-like vibration machine body at controlled mixing and motion of bulk material along the section of U-like body is intensively removed by convective drying method using the hollow branch pipe with gas-distributing holes. [ABSTRACT FROM AUTHOR]