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![Figure 5: Active solar cabinet dryer [39].](profile/Samit-Jain/publication/333080865/figure/fig5/AS:758411113283585@1557830708214/Active-solar-cabinet-dryer-39_Q320.jpg)
Solar drying of agricultural produces has long been used for preserving the produce at farmer's end. However, there are several disadvantages of solar drying too. Degradation in food quality is common as the produce is directly exposed to solar radiation. Crops laid for drying in the open can be damaged by birds, animals, dew or rain or they can be...
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... and dust layers) and the path length of the beams through the atmosphere. The global radiation is shown in Figure 1. ...
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... size of the chamber is 4.8 m in length, 1 m width and 0.6 m in height. The four collectors are set in series (Figures 10a and 10b). The collector area is 11.52 m 2 , the mass flow rate is between 0.05-012 kg/s and the average drying temperature is 50°C to 65°C. ...
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... exhaust fan of 20 cm diameter was manually controlled by a valve, allowing the choice of the desired air mass flow. The fan was fixed below product trays at the bottom of the dryer to check an even distribution of air and to remove the humidity of the product to the surrounding (Figure 11). ...
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... air was then passing through the condenser where it was reheated by the condensing refrigerant and then to the drying chamber. Lemon grass was used as the drying material ( Figure 12). ...
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... driving force is directly proportional to the evaporation rate of water to air. However, drying at high temperature is not suitable for the materials which are sensitive to heat because it can cause cracks, browning which further reduce the taste of final product as well as the evaporation of the active ingredients such as in medicinal herbs ( Figure 13). Yahya et al. [28] have developed a solar dehumidification system for medicinal herbs has been developed. ...
Citations
... La energía solar calienta los granos y el aire circundante, lo que provoca la evaporación de la humedad. Es un método de bajo costo y ampliamente utilizado en áreas con alta radiación solar [20]. En la ¡Error! ...
... De igual forma se requiere mantener un control adecuado de la temperatura y la humedad en el área de secado para evitar un secado excesivo o insuficiente. Se pueden utilizar ventiladores o aberturas ajustables para regular el flujo de aire y mantener una temperatura y humedad relativa óptimas [20]. En consecuencia, el tiempo de secado varía según el tipo de material, la humedad inicial y las condiciones climáticas; durante el proceso, se monitorean regularmente los cambios en la humedad de los granos para determinar cuándo alcanzan el nivel de humedad deseado [22]. ...
El secado de granos es un proceso crucial en la cadena de producción de alimentos, ya que permite reducir el contenido de humedad de los granos para su posterior almacenamiento y comercialización. Sin embargo, los métodos de secado convencionales pueden ser costosos, ineficientes y poco sostenibles. Por esta razón, en los últimos años ha habido un creciente interés en el uso de sistemas no convencionales de secado de granos, que ofrecen una alternativa más económica, eficiente y sostenible [1]. De tal forma, estos son una alternativa cada vez más importante y relevante para los productores de granos. En comparación con los métodos de secado convencionales, los sistemas no convencionales tienen una serie de ventajas significativas que hacen que su uso sea cada vez más atractivo en la producción de alimentos [2]. Es de resaltar que los métodos de secado no convencionales suelen ser más económicos y eficientes que los métodos de secado convencionales. Estos sistemas no requieren el uso de combustibles fósiles ni la construcción de instalaciones costosas, lo que se traduce en un ahorro significativo de recursos y costos para los productores [3]. De igual forma, los sistemas de secado no convencionales pueden mejorar la calidad del grano. Estos métodos suelen operar a temperaturas más bajas que los sistemas convencionales, lo que permite mantener la calidad y las características nutricionales del grano. Además, el uso de estos sistemas también reduce la exposición del grano a agentes contaminantes y a la proliferación de hongos y bacterias [4]. Por último, los métodos de secado no convencionales son más sostenibles que los métodos convencionales. Estos sistemas no generan emisiones contaminantes y reducen la dependencia de los combustibles fósiles, lo que los hace más amigables con el medio ambiente y más respetuosos con la salud de los trabajadores y los consumidores [5]. En este contexto, esta tesis se enfoca en los sistemas no convencionales de secado de granos, analizando su eficacia en términos de reducción de humedad, calidad del grano y sostenibilidad, en comparación con los sistemas de secado convencionales. La tesis tiene como objetivo proporcionar una evaluación detallada de estos sistemas no convencionales y determinar su capacidad para satisfacer las necesidades de los productores de granos en Colombia. La investigación se basó en una revisión exhaustiva de la literatura existente, así como en la recolección de datos secundarios como artículos científicos y técnicos. El resultado final de esta tesis es un análisis riguroso de los sistemas no convencionales de secado de granos, su eficacia en diferentes contextos y su potencial para mejorar la productividad y sostenibilidad en la producción de granos en Colombia. Es de recalcar que este es un tema de gran relevancia e importancia en el contexto de la producción de alimentos en Colombia, y proporciona una evaluación detallada y rigurosa de los sistemas no convencionales de secado de granos. Los resultados de esta investigación pueden ser de gran utilidad para los productores de granos, los expertos en el campo del secado de granos y otros actores relevantes en el sector agroalimentario en Colombia 2. Características del Proceso de Secado de Granos El proceso de secado de granos es esencial en la agricultura y un paso crucial en la cadena de producción de alimentos. Durante este proceso, se reduce el contenido de humedad de los granos para preservar su calidad, puesto que se previene el deterioro y garantizar su almacenamiento seguro. En la tabla 4 se presentan algunas características clave del proceso de secado de granos. Tabla 1. Matriz de revisión bibliográfica del proceso de secado de granos Factores Descripción Referencia Contenido de humedad
... Distribusi pressure yang merata dalam solar dryer tersebut menunjukkan tidak ada pressure drop yang diakibatkan kesalahan desain. Adanya pressure drop mengakibatkan pengeringan yang tidak sempurna dalam dryer (Tiwari, 2016). Terlihat dalam fan atas dryer meningkat karena adanya penambahan kecepatan udara yang disebabkan oleh fan yang memasukkan udara. ...
In a previous study conducted by Simo Tagne to designing a solar dryer based on mathematical equations for iroko wood in Cameroon, Africa. However, there is no complete simulation of the drying process on the tool, resulting in the lack of detailed elaboration of the iroko wood drying process. The purpose of this study is to simulate in detail the drying process on the tool using an ANSYS simulation. The model used in this simulation still uses the same mathematical model that has been studied before. This research begins by setting up the ANSYS application with the previous mathematical model, environmental conditions, and tool specifications. Furthermore, simulations are carried out using the ANSYS application with measurements of pressure, temperature, velocity and mass transfer. From this simulation obtained results for the distribution of pressure, temperature, velocity, and mass transfer. From all these distributions, it is sufficient to describe the drying process of the tool according to the mathematical model that has been studied previously.
... 7 Open sun drying has many limitations like high-labour costs, large area requirement, unable to control the drying process, deterioration because of insects and microorganisms and moreover the quality of the dried product is far below international standards. 8,9 Solar drying provides an opportunity to produce quality dried products and is an effective system that utilizes the energy of the Sun for drying 10,11 The usage of solar dryers is increasing day by day as they have special economic attractions. 12,13 Mehta et al. 14 pre-treated and dried mint leaves by various drying methods viz. ...
Coriander (Coriandrum sativum L.) is a highly perishable crop with a shelf‐life of a few days under refrigerated conditions. Solar drying is one of the economical, hygienic and eco‐friendly methods of food preservation. During this study, fresh coriander was pre‐treated in a solution of 0.1% magnesium chloride, 0.1% sodium bicarbonate and 2.0% KMS for 15 min before solar or open sun drying. There were two types of solar dryers used, namely: PAU advanced domestic solar dryer and PAU domestic solar dryer. Solar dryers were evaluated and compared with open sun drying for drying kinetics, thermal efficiency, and product quality. The quality parameters determined were total color difference, total flavonoid content, total chlorophyll content, and ascorbic acid content. For drying of coriander, ADSD achieved the maximum thermal efficiency (18.56%) and minimum solar energy input (12.56 MJ/kg) out of the various drying systems under consideration. Additionally, ADSD samples had the highest quality retention in terms of the highest total flavonoid content (1.23 mg/100 g), total chlorophyll content (24.14 mg/100 g) and ascorbic acid content (24.29 mg/100 g).
... Moisture held in loose chemical combination, present in the product matrix or even trapped in the microstructure of the solid, which exerts a vapor pressure less than that of pure liquid is called bound moisture. Moisture in excess of the bound moisture is called unbound moisture (Tiwari 2016). There are different methods used for drying dates and other agricultural products as well as fish in Oman. ...
The water and soil salinization, economic and vital importance of water, and nutritional value of nitrogen fertilization make it expedient to establish this work which investigated the interaction between nitrogen fertilization and saline water irrigation. The experiment was undertaken in an arid region to compare the performance of four contrasting barley genotypes and select the most efficient one that can be irrigated by brackish water. Barley genotypes were irrigated with two water salinity levels (1.8 and 9.2 dS/m), and four N fertilizer levels were applied (0, 50, 100,150 KgN/ha). Results highlighted the corrective effect of nitrogen on saline water. Data showed a significant reduction (P < 0.05)—caused by saline water—in the number of fertile tillers (38%) and leaves (10%), chlorophyll content (10%), and biomass production (12%); leading to a decrease in grain yield by 6.3 Qx/ha. These reductions were observed in all genotypes with variable rates. On the other hand, nitrogen application showed a significant increase (P < 0.05) in the number of fertile tillers (28%) and leaves (5%), chlorophyll content (8,3%), and biomass production (NDVI value) by 40%. Data showed that the improvements caused by N addition were more evident under salt stress. Our results showed that the inhibitory action of saline water has been significantly reduced by nitrogen fertilization. This makes it possible to predict the corrective effect of nitrogen on the vegetative development and grain yield under saline conditions with an adjusted nitrogen level.
... The high cost of traditional energy resources makes it increasingly necessary to use alternative energy sources to reduce energy intensity and increase the efficiency of technical equipment in agricultural production [7][8][9][10][11][12][13][14][15][16][17][18]. Combined types of dryers with different sources of thermal energy are often used [19][20][21][22][23]. ...
... . ( ) = 0 с.э ( ) + 0 , (17) where a0, b0 -empirical factors; с.э ( ) = .э 2 + с.э + с.э (18) where ac.э, bс.э, сс.э -empirical factors. ...
... where a3 ,b3 -empirical factors. Then, taking into account expressions (13)(14)(15)(16)(17)(18)(19), equation (12) will have the form: ...
Today, the use of aerodynamic dryers for drying various types of fruit crops is very current. In them, the electric energy spent on the drive of the centrifugal fan is transformed into thermal energy due to the mutual friction of the air flows circulating in the closed chamber. In order to increase the energy efficiency of the drying process, the heat of the waste drying agent was used in the research. The presented dryer was equipped with a combined heat exchanger. In order to predict the thermal performance of the combined heat exchanger depending on external factor variables, the dependence of the temperature of the fresh drying agent at the outlet of the combined heat exchanger on the dryer operation time is theoretically determined on the basis of the heat balance equation. The air solar collector in the combined heat exchanger made it possible to increase the temperature of the drying agent at the outlet by another 10oC without extra costs of electrical energy. A comparative analysis of the results of experimental and theoretical studies showed their high convergence.
... The extent of hybrid solar drying system is to deliver a strong final result of a specific level of moisture content of agricultural material for instant use or for a long-term safe storage within a confined time [1][2][3]. ...
In numerous under developed and developing countries, agrarian biological products are dried in open sun and this system of drying diminishes the exceptional quality, widespread acceptance and standard of the dried products because of hindrance from external contaminations, excessive ultra violet radiation and uneven drying rates. Decreasing petroleum derivative saves and expanding impacts of evolution global climate change environmental change because of ozone harming substance discharges have prompted a phenomenal worldwide interest in sustainable wellsprings of energy in food processing. A main competitor among these arising innovations is the change of sunlight to electric power as a substitute and steadiness for sun oriented drying framework. This process can be accomplished directly with sun powered cells (utilizing the photovoltaic impact) or indirectly by concentrating incident solar radiation to generate high-quality heat, which then supports heat production in conventional solar dryers. Various types of solar dryers have been designed and developed in different regions of the world, offering exclusive technical performances. In the hybrid solar dryers, the drying process is successful even under ominous atmospheric conditions. In this assessment paper, we reviewed unique forms of hybrid oriented solar dryers with respect to unique layout adjustments to be able to increase their effectiveness and thermal stability.
... The extent of hybrid solar drying system is to deliver a strong final result of a specific level of moisture content of agricultural material for instant use or for a long-term safe storage within a confined time [1][2][3]. ...
In numerous under developed and developing countries, agrarian biological products are dried in open sun and this system of drying diminishes the exceptional quality, widespread acceptance and standard of the dried products because of hindrance from external contaminations, excessive ultra violet radiation and uneven drying rates. Decreasing petroleum derivative saves and expanding impacts of evolution global climate change environmental change because of ozone harming substance discharges have prompted a phenomenal worldwide interest in sustainable wellsprings of energy in food processing. A main competitor among these arising innovations is the change of sunlight to electric power as a substitute and steadiness for sun oriented drying framework. This process can be accomplished directly with sun powered cells (utilizing the photovoltaic impact) or indirectly by concentrating incident solar radiation to generate high-quality heat, which then supports heat production in conventional solar dryers. Various types of solar dryers have been designed and developed in different regions of the world, offering exclusive technical performances. In the hybrid solar dryers, the drying process is successful even under ominous atmospheric conditions. In this assessment paper, we reviewed unique forms of hybrid oriented solar dryers with respect to unique layout adjustments to be able to increase their effectiveness and thermal stability.
... The dryers are waterproof; therefore, the food does not need to be moved during rain. 11 A solar biomass hybrid dryer with heat energy from solar radiations and fossil fuel or biomass is needed for drying agricultural products. 12 A solar biomass hybrid dryer (SBHD) is operated with an external heat source, such as a furnace that runs on biomass, thus making the drying process independent of weather conditions. ...
BACKGROUND
Aflatoxin‐contaminated grain consumption over the years has been known to result in serious health hazards for its consumers. The present study investigated the effects of harvest seasons and drying methods on aflatoxins in freshly harvested maize. A 2 × 3 × 3 × 3 × 3 factorial design was used; two harvesting seasons (dry and wet), maize varieties (P3966W, P4063W and P4226), moisture contents (0.15, 0.12, and 0.10 g kg⁻¹), modern fabricated solar dryer (MFSD), hybrid biomass dryer (HBD) and open‐air drying (OAD) methods, and packaging materials (plastic, jute and polyethylene bag) were studied, respectively. In total, 162 samples (n = 162) of maize grains (250 g each) were dried. The freshly harvested maize was shelled, dried, stored and analyzed for aflatoxins using high‐performance liquid chromatography. The data obtained were subjected to statistical analysis.
RESULTS
P3966W and P4063W with an initial moisture content of (0.226 and 0.234 g kg⁻¹) reached a safe level of 0.10 g kg⁻¹ using MFSD within 2–3 days, HBD within 2–3 days and OAD within 5 days. Variety P4226 with an initial moisture content of 0.228 g kg⁻¹ reached a safe moisture level of 0.10 g kg⁻¹ in 2, 3, and 7 days using MFSD, HBD and OAD, respectively. Aflatoxin concentration (56.00 ± 8.89 μg kg⁻¹) was highest in P4063W at 0.15 g kg⁻¹ moisture content, which exceeded the maximum permissible limits of 4 μg kg⁻¹ recommended by the World Health Organization.
CONCLUSION
Variety, type of dryer and season affect aflatoxin contamination of maize. The adoption of MFSD drastically reduced the duration of drying and consequently controlled contamination by aflatoxins. © 2022 Society of Chemical Industry.
... It was probably the first ever food preserving method used by man before cooking (Alamu et al., 2010). Drying of agricultural products can be described as the removal of moisture from a product thermally to yield solid product (Tiwari, 2016) or the removal of some moisture from crop by mechanically moving air through the crop after it has been harvested. ...
The quest for improved performance of access to solar dryers has led to the development of several designs of solar dryers. This study evaluated the performance of the Dehytray TM , a relatively new solar dryer made up of food grade plastic, in comparison with sun drying using plantain, okra and pepper as test crops in five replicated trials. Freshly harvested crops were divided into two batches, weighing 1.3 kg each. The first batch was blanched with salty water (7 g/100 g) for 2 to 4 min while the other was unblanched. Fresh, sun-dried and solar dried samples were analyzed for their proximate composition and microbial load using standard methods. Drying efficiency was determined using standard equations while three thin layer drying models were applied to the experimental data compared according to their coefficient of determination (R 2) and root mean square error (RMSE), predicted by non-linear regression analysis using Microsoft Excel solver, 2018. Mean temperatures ranged from 55-65°C and 25.5-34.3°C for Dehytray TM solar dryer and sun drying, respectively. Efficiency of the dryer ranged between 16.6-28.1% (blanched) and 16.3-33.7% (unblanched) for plantain, 18.2-29.8% (blanched) and 19.4-28.8% (unblanched) for okra and 11.7-17.8% (unblanched) and 11.2-17.7% (blanched) for pepper. Efficiency of the sun drying ranged from 1.1-2.1% (blanched) and 1.4-2.3% (unblanched) for plantain, 1.3-3.1% (blanched) and 1.6-3.7% (unblanched) for okra and 0.7-0.9% (unblanched) and 0.7-1.1% (blanched) for pepper. There was a good retention of nutrients on the solar dried crop compared to that of the sun-dried crop. Mean airflow rate in the Dehytray TM was 0.021 m 3 /s compared to 0.49 m 3 /s in the sun drying. The portability and performance of the Dehytray TM makes it a viable option in the humid tropics.
... Heat transfer from the surrounding environment provide required energy to moisture movement inside the product and evaporate the moisture from the surface. During mass transfer, internal moisture is transferred to the surface of the solid by diffusion mechanism and subsequently is evaporated by convective transfer phenomena due to application of energy (Tiwari, 2016;Beigi, 2016). These phenomena are particularly occurred under transient conditions between a moist object and heat source. ...
... These phenomena are particularly occurred under transient conditions between a moist object and heat source. The moisture removal the material surface as vapor from depends on the external conditions such as temperature, air humidity and flow, area of exposed surface, and pressure (Darvishi et al., 2018), while the moisture diffusion and movement inside the solid is mainly a function of the physical nature and moisture content of the solid (Tiwari, 2016). ...
In the present work, moisture removal characteristics of quince slices in a convective tray dryer were studied. The blanched slices (with thicknesses of 3, 5 and 7 mm) were dried at drying temperatures of 50, 60 and 70 °C and air flow rates of 1, 1.5 and 2 m/s. The analytical model proposed by Dincer and Dost was used to determine the mass transfer parameters. The obtained Biot numbers (0.108‒0.293) revealed that both the internal and external resistance control the moisture diffusion within the samples. The moisture diffusivity and convective mass transfer coefficient were found to be in the ranges of 1.578×10-7‒7.331×10-7 m2/s and 2.040×10-5‒3.507×10-5 m/s, respectively. The activation energies for moisture diffusion and surface mass evaporation were determined to be in the ranges of 17.607 to 48.019 kJ/mol and 5.270 to 27.430 kJ/mol, respectively.
