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Abstract This paper presents a dynamic model of a solar dryer for agro-products with thermal energy storage system, using paraffin wax as phase change material. The mathematical model of the dryer was separated in three stages: a solar panel, a solar accumulator and a drying chamber. The system of equations was solved using numerical integration. The models were validated with experimental data reported in previous studies on the drying of kiwifruit and mushrooms. Temperature s was measured at the outlet of the solar panel and solar accumulator, solid moisture content and air humidity were measured at the inlet and outlet of the drying chamber. Based on fit evaluations R2 and RMSE, the model accurately predicts temperature and humidity of the drying air, temperature and moisture of the product, behavior of the heat transfer and drying parameters and time variable climatic conditions ambient temperature, air humidity, and solar radiation. Highlights • Thermal efficiency can increase for solar dyers equipped with phase change material. • The use of PCM extends operation time into periods of low or no radiation. • A dynamic model of a solar dryer for agro-products with energy accumulation was presented. • The mathematical model integrates the behavior of the solar panel, solar accumulator and drying chamber. • Based on residual analysis the models accounted for experimental data satisfactorily. [ABSTRACT FROM AUTHOR]

The objective of the present investigation was to computationally model a typical solar dryer for coffee, considering some alternative geometric configurations in the opening of windows to improve the thermal conditions within the drying structure which enable the water removal process of wet parchment coffee. The model was simulated in Ansys CFX® software. Simulation results showed that the geometry with an opening of 25 % in the air output window increased temperature in the coffee layer to 4.2 °C over room temperature, guaranteeing uniform drying, whereas the typical geometry with a 100 % opening increased temperature to 3.8 °C. When the maximum window opening for input and output of air was used, the relative humidity of air within the dryer decreased in comparison with the other geometries. [ABSTRACT FROM AUTHOR]

The main aims of this work are fabricating simple solar dryer for tomatoes fruits drying, solar dryer and open solar drying were used to dry tomato slices, and study of drying time influences on moisture content losses and weigh of tomatoes slices. Also, to study various parameters such as relative humidity, temperature and velocity of air on tomatoes drying and compared to solar dryer and open solar dried during tomatoes fruits drying. Tomatoes are sliced to a thickness of about 1, 1.5 and 2.5 cm. The sliced tomatoes are arranged in single, two and three layers on surface of mats and left to dry naturally in the open solar and in solar dryer. Tomatoes dried at a time vary, based on the thickness layers of slices. Obtained results were: - The weight of all tomato slices was decreased by increasing drying time in opened solar drying and inside fabricated solar dryer. The weight of dried tomato slices was lower under the drying inside fabricated solar dryer than the drying in opened solar drying method. - The losses of moisture content of all tomato slices were increased by increasing drying time in opened solar drying. But, the losses of moisture content of dried tomato slices were higher under the drying inside fabricated solar dryer than the drying in opened solar drying method. Because of the moisture content of all tomato slices was decreased by increasing drying time in opened solar drying. But, the moisture content of dried tomato slices was lower under the drying inside fabricated solar dryer than the drying in opened solar drying method. The solar dryer appears to be the effective and faster method of drying of tomatoes slices, because the drying time is very less compared with open solar drying. This is due to the solar drying effect inside the solar dryer where the temperature inside the dyer keeps on increasing with decrease in relative humidity inside the dryer. [ABSTRACT FROM AUTHOR]

Solar food drying is a well-established food-conserving process in India. Various researchers had developed solar dryer models which were usually validated using experimental observations and numerical simulation processes that are time-consuming and money-consuming. Computational fluid dynamics (CFD) simulation software facilitates the simulation of the models and gives same results in a comparatively small frame of time. This research paper is focused on CFD simulation, validation of design, energy analysis and numerical computation for domestic direct-type solar dryer for which experimental observations were performed at Ludhiana in November 2006. The design and simulation of the domestic direct-type multi-shelf dryer at no load condition are performed using ANSYS Fluent 14.0 software. The temperature of the air inside the dryer is found to be 326 K, which validates the design and purpose of the domestic direct-type multi-shelf dryer. The embodied energy of the constituents used in the construction of dryer is obtained as 339.015 kWh, and the energy payback time and carbon credit are found to be 7.57 years and INR 2055, respectively. The convective heat transfer coefficient for the dryer varies from 2.4 to 2.8 W m−2 °C−1. Coefficient of determination is estimated to be 0.98 under no load condition which shows the fare agreement between predicted and experimental value. [ABSTRACT FROM AUTHOR]

Abstract The shortages in conventional fuels along with the continuous rise in their prices have led to an increased emphasis on using solar energy as an alternative source of energy. However, establishing reliable and affordable solar collectors for different applications is a great challenge. Therefore, this study aimed to design and fabricate an efficient and cheap solar air collector from recyclable aluminum cans. Two dryers of different configurations (closed and open modes) were then constructed and examined for drying tomatoes under different operating conditions. The results revealed that the thermal efficiency of the designed solar collectors increased considerably from 25 to 63% when the air-flow rate increased from 15 to 45 m3h-1. In comparison to the conventional method of open sun drying, the designed solar dryers enhanced both the drying rate and the overall quality of the final product. In the designed solar dryer, over three days of consecutive drying (30 h of drying), the moisture content of tomato wedges was reduced from 19 to less than 1 kg [H 2 O] kg−1 [dry matter]. The closed-mode dryer configuration, which recirculates the drying air, showed a considerable increase in the drying rate and weigh loss over the traditional sun dryers and open-mode dryer systems. Among all mathematical models, a non-linear quadratic model (Wang and Singh model) has shown a better fit to the experimental drying data compared to the other models. Highlights • A solar collector was fabricated from recyclable aluminum cans. • Two solar dryers were constructed and examined for tomato drying. • Thermal efficiency of 65% was reached under the tested air flow rates. • Increasing the air flow rate increased the thermal efficiency and the drying rate. • Using recyclable materials to build solar collectors implied lower costs and cleaner environment. [ABSTRACT FROM AUTHOR]

Abstract Performance of a collector in solar dryer, equipped with porous and recycling system was investigated at three airflow rates (0.009, 0.018 and 0.036 kg/s). The CFD model was applied for developing the thermal response simulation of the collector for outlet air temperature, energy and exergy parameters. The predicted and experimental data were analyzed. The results illustrated a quit good correlation between the predicted data by CFD model and experimental data. The maximum energy and exergy efficiencies were 63.4% and 22.3%, respectively, for mass flow rate of 0.009 kg/s. In general, porous and recycling system not only improved the thermal efficiency of the dryer, but also accelerated the drying time. The energy and exergy efficiencies of the collector with porous and recycling system were about 19.1% and 19.5%, respectively higher than the energy and exergy of the collector without them. The maximum total thermal energy of the collector (21.24 MJ) was produced at the airflow rate of 0.009 kg/s. No adverse effect was found on the quality of the dried products with employing of porous and recycling system in solar dryer. Highlights • The simulation of a solar collector with new structure investigated using CFD model. • Porous and recycling system increased energy and exergy efficiencies of the collector about 19.1% and 19.5%, respectively. • Using a solar collector with porous and recycling system increases drying efficiency up to about 50%. • Application of porous and recycling system in solar dryer improved the quality of the dried product. [ABSTRACT FROM AUTHOR]

Abstract In this study, a solar powered indirect food dryer is designed and developed. The dryer design consists of a solar collector unit, drying chamber with two columns of four rack shelves, chimney for the exhaust air, and a solar powered fan. The outlet of the dryer is designed in a truncated pyramid geometry so that precipitation of condensed water would be minimized and additional heating of the drying air is possible at the exit. The dryer is developed and manufactured in Mekelle, Ethiopia. Computational Fluid Dynamics, CFD is employed for predicting a transient three dimensional flow field and temperature distribution within the drying chamber using a symmetric flow domain. The predicted air flow distribution in the vicinity of the rack shelves showed that the mean flow velocity is 0.14 m /sec for the lowest shelf and 0.12 m /sec for the other shelves due to cooling of the air. A significantly uniform airflow distribution is observed on the top three shelves compared to the bottom shelf. The inside of the drying chamber evolves towards a steady operating temperature of 315K. The temporal temperature distribution reveals that the food to be dried will evolve to this temperature in about 35 minutes. For validating the model, the temperature distribution on each rack shelf is measured along with the global solar irradiation. The maximum average temperature difference between the measurement and the CFD simulation is found to be 4.3 °C. Hence, the CFD model is able to produce a good qualitative and quantitative insight into the temperature distribution within the drying chamber, rack shelves, and symmetry plane. [ABSTRACT FROM AUTHOR]

Solar energy has great potential as an alternative energy source, but variations in solar radiation require the use of additional energy sources to maintain a continuous drying process. We developed a process for drying kiwifruit using a solar dryer and an energy accumulation system with paraffin wax as phase change material. The final moisture content, total polyphenols, and antioxidant capacity were evaluated and compared with freeze drying. The analyzed experimental factors were kiwi slice thickness and the use or nonuse of fuzzy logic control systems to regulate the air flow through the devices. Critical moisture content, shrinkage, solar panel, and solar energy accumulator efficiencies were calculated. In addition, five empirical models were fitted to the drying curves. The solar panel showed an efficiency between 56 and 76%. The use of the fuzzy logic control system extended the period of available energy, thus prolonging the use of the solar panel and solar energy accumulator and using only 10% of the stored energy; otherwise, without the control system, 43% of the stored energy was used. The highest drying rates were achieved for kiwifruit slices 4 mm thick, using the solar dryer with the control system. The loss of polyphenols and antioxidant capacity were minimal for kiwifruit slices of thickness 8 mm without the control system. [ABSTRACT FROM AUTHOR]

-Solar dryers are cutting-edge equipment that uses solar energy to remove moisture from various materials, including agricultural produce, textiles, and industrial components. It is carried out by employing fossil fuels in an artificial mechanical drying process or by leaving the produce in the open sun. The first approach is expensive and detrimental to the environment, whereas the second option completely depends on the weather. These dryers use the sun's energy to generate a controlled drying atmosphere, promoting effective moisture removal while lowering energy consumption and environmental impact. The literature review substantiates that indirect and mixed-mode solar dryers with phase change material have more potency in drying agricultural products than direct-drying solar dryers. The mixed-mode tent-type solar dryer decreases the moisture content of the fish from 89 % to 10 % in 18 h, while it takes 38 h when compared with an open sun dryer. According to the market forecasting analysis, the global solar dryer market was valued at USD 3.5 billion in 2023 and is predicted to increase at a compound annual growth rate of 10.6 % from 2023 to 2031. The primary goal of this review study is to provide an overview of the current advancements made by various researchers in solar dryers. Therefore, the contribution of researchers is globally updated from 2016 to 2021, while section five discusses the miscellaneous influence factors on solar dryers with the latest literature review, 2022–2023. [Display omitted] • The contribution of solar dryers is updated globally for the years 2016–2021. • Research contribution from 2022 to 23 has been segmented separately. • The limitations and advantages of solar dryer methodologies are succinctly summarized. • A year-wise summary has been presented for solar dryer technology advancement. • A future scope to enable IoT applications for solar dryers is presented. [ABSTRACT FROM AUTHOR]

The present research deals with the analysis of 3-dimensional computational models to analyze the airflow, temperature profile of dryer coupled with heat transfer of pineapple slices during solar drying. A finite element approach performed the simulations of mixed-mode solar dryers integrated with flat plate and finned collectors consisting of baffles and semicircular loops under forced convection using COMSOL Multiphysics software. The mass transfer of pineapple slices was also simulated to compare the moisture distribution inside the samples dried in both solar dryers. The dryer integrated with flat plate collector (FPSC) presented 2.5 h longer drying period than the finned collector assisted dryer to attain the 10% (wb) moisture of pineapples slices. The airflow pattern indicated inadequate air distribution inside the FPSC and generated two vortices contributing to dead zones and localized heating inside the drying chamber. The finned collector provided a more effective air distribution in the dryer. The sample's temperature was greatly affected by their position because of non-homogenous temperature distribution in FPSC-Dryer and finned collector integrated dryer presented more uniform temperature profile. The results are beneficial for the analysis of uniformity of airflow and temperature in the dryer, which is a deciding factor for homogeneity of drying. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction Drying is one of the most common methods for storing food and agricultural products. During drying process, free water that causes the growth of microorganisms and spoilage of products is removed from the product. There are several methods for drying of agricultural products. one of the most important methods of investment is drying by using sunlight. Iran is situated at 25- 43oE longitude and mean solar radiation is about 4.9 kwh.m-2.d-1. Because of the proper solar radiations in 95% of the agricultural areas in Iran, solar drying is widely used for drying of fruits and vegetables. The use of solar dryer causes saving in energy consumption and processing costs for drying of products in farms and gardens. Several researchers investigated heat transfer and heat flow in dryers. Selection of appropriate method was carried out for drying of agricultural products using heat pump. Experiments were done and mathematical relationships were estimated to obtain correlation parameters between Reynolds number and Nusselt number for the three cases of solar dryer (cabinet, indirect and combination).The best working conditions were determined for three types of solar collectors (flat, finned and corrugated). In this study, the process of heat transfer and heat transfer coefficient of a solar dryer with and without rotation of absorber plate was compared. Materials and Methods The experiments were conducted in Azarshahr, East Azarbayjan province, Iran in September 2014. Newton's law of thermodynamic was used to analyze the working condition of solar absorber. For this purpose the absorber plate was divided into four equal parts. According to the thermal equations and related boundary conditions as well as the relationship between heat transfer coefficient and the temperature gradient, equation 1 for the Nusselet number obtained: 1 Beside the relationship between Nusselt number and heat transfer coefficient is defined as equation 2: 2 Finally variation of total heat flow over the time at different surfaces of the collector is determined by using equation 3: 3 Two cases (solar panel with rotation and without rotation) were considered for testing. Data measuring was carried out for 9 hours from 8 to 17. The fluid flow rate was 0.0185m3.s-1. The dryer was installed in an environment with air temperature of 31.6 oC and 31.8 oC, with the air velocity of 0.58 m.s-1 and 0.54 m.s-1 and with the relative air humidity of about 21%and 21.5% at the first and second days, respectively. The dryer had an automatic temperature controller to fix the air temperature with an accuracy of ±0.1 oC. An anemometer Yk-2005AM model was used to regulate the required air velocity. The output data of the thermocouples was recorded by a digital thermometer (DL-9601A, Lutron) that was connected to a computer using RS232 cable and recorded the temperature at required point every an hour. The relative humidity of the ambient was measured every hour with a digital hygrometer (HT.3600, Taiwan), accuracy of 3%. By assembling controlling system with a DC motor, a precious photocell and a proper mechanism, the frame would rotate by the sun and followed solar radiation, therefore more solar energy produced in solar panel. Results and Discussion The results of the experiments showed that the heat transfer process increased in both cases from the early morning and reached to its maximum value around 12 to 14 o’clock. The trend was more homogeneous in the dryer by absorber plate without rotation due to the decline of the heat accumulation. The mean temperature rise in the solar dryer without rotation was 37oC and in the solar dryer with rotation was 54oC. Because of the rotation of solar plate, variations of solar radiation were low. Therefore, by rotation of the solar dryer panel the temperature rise was 27oC. The values of heat transfer coefficient in the solar dryer with rotation were decreased by the time. This reduction in the hours before noon is more than after noon. This is due to the reduction of the temperature gradient in the solar absorber plate. Also the results showed that heat transfer coefficient in the lower levels (S1 and S2) is more than higher levels (S3 and S4). Variations of the heat flow for the solar dryer with rotation is more than the other. Because in the first one, the absorber plate was followed the solar radiation and generated heat in the plate increases and the fan does not have the ability to discharge the generated heat. The total amount of heat transfer in absorber plate with rotation was 36.1% higher than the absorber plate without rotation. To increase the heat transfer from the dryer, design of the system to change air flow rate by increasing temperature, can increase the efficiency of the dryer. Conclusions In this study the performance of the absorber plate in a solar dryer in two cases with rotation and without rotation were compared. The results showed that by rotation of the solar absorber plate the output temperature of the collector rises about 27oC. Thermal fluctuation in the rotation solar plate is lower than the solar plate without rotation.

Mathematical modelling and effective moisture diffusivity of tomato (Lycopersicon esculentum) was studied during hot air solar drying. An experimental solar dryer with a swivel collector was used for experiments. The collector followed the solar radiation using a precious sensor. Drying experiments were performed in a thin layer hot air drying at slice thicknesses of 3, 5 and 7 mm and air velocities of 0.5, 1 and 2 m/s. The experimental data were fitted to different mathematical moisture ratio models and the Page model was selected as the best model according to correlation coefficient R2, chi-square χ2 and root mean square error (RMSE) parameters. The maximum values of moisture diffusivity was 6.98 × 10-9 m2/s at air velocity of 2 m/s and slice thickness of 7 mm while the minimum value of the moisture diffusivity was 1.58 × 10-9 m2/s at air velocity of 0.5 m/s and slice thickness of 3 mm.

A theoretical and practical study was conducted for the vacuum solar dryer, which locally manufactured to drying of salted and unsalted carp Fish and compared with natural sun drying and vacuum electric dryer in Basrah province for the period from October 2011 to July 2012. The study included simplifying the Crank’s equation to predict the theory moisture content compared with practical data. Solar radiation intensity, temperature in the atmosphere and in the solar dried were measured. The results indicated a convergence is too big between the theoretical and practical moisture content and coefficient of determination ranged between 0.8848-0.9503. The average temperature in the solar dryer 50°C in all days of the year with sunny weather while on cloudy days, the temperature in the solar dryer reached to 43°C with fluctuations in solar radiation intensity. The moisture content results of dried Fish by vacuum solar dryer and vacuum electric dryer were convergent but it is significantly better than natural sun-drying method

Drying characteristics of cassava slices was investigated in a mixed mode natural convection solar dryer to obtain a suitable mathematical model describing the drying. The average drying chamber temperature was between 34 ±2 °C and 50 ±1.8 °C, while 10 commonly used thin layer drying models were used for drying curve modelling. Coefficient of determination (R2) and root mean square error (RMSE) were used to determine the models performances. The drying curve of cassava slices showed a reduction of moisture content with increased drying time in the solar dryer, and the variation of moisture ratio exponentially decreased with increased drying time. The Midilli and Logarithmic models showed better fit to the experimental drying data of cassava slices. As compared with other models tested, there were no significant differences (p >0.05) in the R2 values obtained for the Midilli and Logarithmic models; hence, the Logarithmic model was preferable because of the lower RMSE. The diffusion mechanism could be used to describe the drying of cassava slices that was found to be in the falling rate period. A diffusion coefficient (Deff) of 1.22 × 10-8 m2 s-1 was obtained, which was within the established standard for food products.

Introduction: Drying process of agricultural products, fruits and vegetables are highly energy demanding and hence are the most expensive postharvest operation. Nowadays, the application of control systems in different area of science and engineering plays a key role and is considered as the important and inseparable parts of any industrial process. The review of literature indicates that enormous efforts have been donefor the intelligent control of solar driers and in this regard some simulation models are used through computer programming. However, because of the effect of air velocity on the inlet air temperature in dryers, efforts have been made to control the fan speed based ont he temperature of the absorber plate in this study, and the behavior of this system was compared with an ordinary dryer without such a control system. Materials and methods: In this study, acabinet type solar dryer with forced convection and 5kg capacity of fresh herbs was used. The dryer was equipped with a fan in the outlet chamber (the chimney) for creating air flow through the dryer. For the purpose of research methods and automatic control of fan speed and for adjusting the temperature of the drying inlet air, a control system consisting of a series of temperature and humidity sensors and a microcontroller was designed. To evaluatethe effect of the system with fan speed control on the uniformity of air temperature in the drying chamber and hence the trend of drying process in the solar dryer, the dryer has been used with two different modes: with and without the control of fan speed, each in twodays (to minimize the errors) of almost the same ambient temperature. The ambient air temperature during the four days of experiments was obtained from the regional Meteorological Office. Some fresh mint plants (Mentha longifolia) directly harvested from the farm in the morning of the experiment days were used as the drying materials. Each experimental run continued for 9 hours, startingat 8:00 am and terminating at 17:00. To determine the moisture content for the purpose of observing and recording the drying process, the drying materials were sampled with one hour time step. The moisture contentwas determinedin the laboratory using the well- known method of oven drying which is presented elsewhere. Results and discussion: Since the ambient air temperature during the four days of experimental runs was almost the same, the effect of ambient air temperature on the drying process was ignored. Considering the dryer inlet air temperature charts obtained in this study (Fig. 2 and Fig. 3), it can be concluded that for those tests using the fan speed control system, the outlet air temperature of the collector during drying period associated with very little variations, is compared with the no control mode runs. At the beginning of the day and also during the hours at the end of the day, due to a decrease in the temperature of the absorber plate compared to the middle of theday, the fan speed is reduced as air passes slowly through the absorber plate and hence the temperature rises. But in the middle of the day, with increasing the temperature of absorber plate, the speed of the fan is increased to provide sufficient airflow and to prevent the absorber plate from warming up. Inexperiments without fan speed control, the fan works with no limitation, and the temperature of the inlet air was changed with the temperature change in the absorber plate. The fan speed control system in addition to lowering the temperature changes in the outlet air, also increased the average outlet temperature about 3C, compared to the dryer without such a control system. During the twodays of experiments, the average ambient air temperature was 28C and at the sametime the outlet air temperature was 40.6 and 40.8C, respectively. In twodays of no control system, the average temperature of the ambient air was 28.5 and 28C and at the sametime the outlet air temperature was 38 and 37.8C, respectively. The results showed that with fan speed control mode the variation of inlet air temperature of the drying chamber was more limited and remained within the range of 39 to 42 and 40 to 42°C during the two experimental days, respectively. However, without fan speed control, the system exhibited a wider variation of inlet drying air temperature and limited within the range of 33 to 44 and 32 to 43°C. Furthermore, with fan speed control in a solar dryer, along with more uniformity in moisture content, the drying rate may speed up and with further decrease in final moisture content up to 8%, when compared to a system with no fan speed control. Conclusions: The average temperatures of the outlet air of collector in two days with fan speed control system, were 40.6 and 40.8°C while in the system without the fan speed control, were 38 and 37.8, respectively. This clearly indicates that the system control could increase the temperature of the collector outlet. The dryer was also able to control the fan speed during the 9hours of drying mint with initial moisture content of 85% (w.b) and to reduce it to about 24.5 and 25.5%, during the two experimental days, respectively. While the corresponding values without the use of a control system were 33.5 and 33.5%, respectively. In other words, in the experiments with the use of control system, the final moisture content was about 8% lower than the moisture content of materials dried without such a system. Furthermore, the control system reduces the volume of air required by the system and hence speeds up the drying process.

Dill is one of the most important plants in the world because of its medicinal properties and it is widely used as a vegetable in the most parts of Iran. In the present study a new solar dryer with finny, perforated absorber plate collector was utilized to dry fresh dill. The dryer was comprised of a solar collector, a product container, a fan and a drying air temperature controller. The temperature controller was used as a control system to regulate the drying air temperature. Thermal performance of the dryer with finny, perforated solar collector was compared with that of a simple flat plate solar collector at different airflow rates. The effect of drying air temperature at three levels (45, 55 and 65 °C), the product size at three lengths (3, 5 and 7 cm) and two different modes of drying (mixed and indirect) on the dryer performance was investigated. The results showed that the finny, perforated absorber plate solar collector could improve the thermal efficiency about 11% in comparison with the flat plate collector and the highest thermal efficiency was achieved at the maximum airflow rate. Meanwhile, increasing the air temperature and decreasing the product size caused a significant reduction in energy consumption. Solar fraction reduced by increasing the air temperature. Finally a maximum dryer efficiency of 70% was observed at air temperature of 65 oC, product size of 3 cm with mixed mode drying.

Considering the wide use of plant anamú for medicinal purposes and in the territory of Santiago de Cuba there is great interest in the development of processes that allow the use of anamú for therapeutic purposes, for which the dried plant is required for this causes work was developed with a view to obtaining a prototype solar dryer for drying the plant. In this paper the calculations were developed for the sizing of the prototype and the elements of the technical project team designed at the Research Center for Solar Energy developed. It also shows the built prototype and its evaluation idle (no load) is also shown. During the evaluation estimation confidence intervals it was determined that the average value of the maximum temperature for the days analyzed, has a value that is between 40,6 and 42,2℃ for a confidence level of 0,95 and the average temperature is between 36,8 and 39,8℃, which are suitable for drying anamú. [ABSTRACT FROM AUTHOR]

Energy is prime and basic need in today's life that why energy consumption has increased day by day and most of the energy demand can be fulfilled by non-renewable energy sources. Hence, there is a need to adopt alternate source of energy. In rural and urban areas, solar energy can be used in a stunning manner through solar cooker and solar dryer. Many textured dryers and solar cooker, electric and mechanical dryers are commercially available in the market for drying and cooking purpose. But they required high capital investment and high maintenance, which make it unsuitable for the use. Here a low cost domestic solar hybrid cum cooker was developed to effectively utilize the alternative source of energy. This one device can either be used as dryer or can be used as cooker. It can also work effectively in cloudy weather or in morning hours. The thermal efficiency of solar was found 28.93 % whereas drying efficiency of dryer was found 34.74%. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of an indirect solar dryer for wood, using an absorber placed directly behind the transparent cover on the top of the dryer with a layer of air separating it from the cover. The floor and north wall are insulated and painted in black. The dryer is very simple to build and electrical energy is only used for the fan. Applications are done on three tropical woods with 50 mm thick most utilized in Central Africa: obeche ( Triplochilon scleroxylon ), iroko ( Chlorophora excelsa ) and sapele ( Entandrophragma cylindricum ). Comparisons between the numerical results and those experimentally obtained are given and the performances of this solar dryer are discussed under the weather conditions of seven towns in Central Africa region located in six different countries. Satisfactory agreement between experimental and numerical results is then obtained. With an average initial moisture content ranging between 0.4 and 0.48 kg/kg, the average final water contents are ranged from 0.15 to 0.18 kg/kg after 21 days in Yaoundé during the months of November and December 2004. Modeling was applied from November 1st to the November 30th, to Sapele wood with 50 mm thick and 0.4 kg/kg initial moisture content dried in Bangui, Brazzaville, Douala, Kinshasa, Libreville and Yaoundé until the final moisture content, which can vary from 0.13 to 0.1 kg/kg. Solar energy per cubic meter of wood was ranging from 2 to 4.3 GJ/m 3 with a maximal thermal efficiency between 12 and 47%. Ndjamena’s climate is not good to use solar drying because of its low air absolute humidity that gives a fast drop in the moisture content and consequently destroys the wood board quality. Bangui, Brazzaville, Douala, Kinshasa, Libreville and Yaoundé give satisfactory alternative drying conditions using the studied solar dryer. However, it is important to use a solar collector in those six towns in order to reduce the effect of the air absolute humidity and improve the drying kinetic. [ABSTRACT FROM AUTHOR]

In an indirect forced circulation solar dyer, solar thermal energy is primarily used for drying the commodities while electrical energy is used for operating the blower/fan to force air through the collector and drying chamber. In few applications, electrical energy is also being used in auxiliary heater to speed the drying process and assist drying during non sun shine hours. The aim of this research work is to eliminate the use of electricity in the indirect solar dryers by utilizing split A/C condenser unit that is placed outdoors. This idea will eliminate the electrical energy requirement for blower/fan to force air in the drying chamber and enable to use thermal energy dissipated from split A/C system as auxiliary heating source. For this purpose, an integrated solar dryer that uses hot air from split A/C condenser was fabricated in house and the drying behavior of sultana grapes was investigated in the present work. Drying experiments were carried out in the locality of Tiruchirappalli (78.6°E & 10.8°N), Tamil Nadu, India during summer months of April and May 2016. The use of split A/C condenser outlet cooling air reduced the drying time of grapes by 16.7% compared with open sun drying method. A possibility of 13% increase in solar dryer efficiency was demonstrated due to the integration of solar dryer with A/C condenser unit compared to the conventional indirect solar dryer. From the experimental results, it was found that the exponential model is capable of describing the drying characteristics of seedless grapes. Predicted values of moisture ratio were in good agreement with experimental values. The exergy analysis indicated increased heat availability inside the dryer chamber. [ABSTRACT FROM AUTHOR]

The present investigation was carried out with the objective of determining the effect of sustainable grape drying methods in water loss, in microbiological and sensorial quality, as well as in the costs incurred due to its use, just to the limitations presented by the current methods. Grape fruits (Vitis vinifera L.) variety Harmony, selected according to characteristics of ideal external quality were used. The methods consisted of osmodehydration + solar dryer, direct drying in the sun (control) and solar dryer. It was corroborated that the direct drying to the sun of the grapes, constituted the longest process to reach 50% of humidity. Regarding the microbiological quality, the direct drying to the sun showed growth of bacteria, while the growth of fungi was manifested in the osmodehydrated grapes and later dried in a solar dryer, showing no development of microorganisms in the solar dryer method, which is sample of guarantee of innocuousness of the product obtained in this way. From a sensory point of view, the general acceptance rate corresponded to fruits previously osmodehydrated in sucrose 53.3ºBrix, however this drying method was where the highest costs were incurred. [ABSTRACT FROM AUTHOR]

Curcuma longa (turmeric) is a rhizomatous herbaceous perennial plant which is widely cultivated in tropical regions, such as Indonesia. It has been intensively used for medical purposes as an ingredient of traditional medicine for a long time. In order to extend its shelf-life, turmeric is generally dried under the sun prior to use. This method generally takes a longer time and is less controlled, thus yielding less qualified products. This experiment was carried out using a manually designed solar dryer for improving the drying process of turmeric. The drying process using solar dryer is shorter and also protects the samples from dirt, insects, as well as direct contact with UV radiation which may deteriorate its bio-active compounds. The drying was done until moisture of about 10% content was achieved. In general, it took about 450 minutes in the solar dyer in comparison to that of 480 minutes using sun drying to reach the equilibrium moisture content. This was caused by a higher temperature profile distributed inside the solar dryer accelerating the drying process. The use of solar dryer has the potential to be further developed to replace the conventional sun drying method of herbs. [ABSTRACT FROM AUTHOR]

This study focuses on the drying of the same quantity of a food product, cut in three different shapes (cylindrical, cubical and rectangular parallelepipedic). The experiments were carried out, considering the solar drying of potatoes. The results show that, the drying kinetics depend, on the shape and the size of items, which constitute each quantity. Using the diffusion model and experimental curves of the drying kinetics, the internal coefficient of diffusion, is identified for each case. Results show that, due to the shrinkage effect, the calculation of this coefficients modified, between the beginning and the end of drying. Relations between these coefficients and the characteristic dimension, are established. The analysis assesses the geometrical factors, which influence the drying parameters. The objective of this work is to propose recommendations for a wide use of solar dryers and to study the feasibility and the exploitation of these clean systems, especially in the Maghreb region. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics model was developed to simulate the corn drying process in a solar cabinet dryer. Incident solar radiation was modeled using a dual-band spectrum to simulate the absorption of shortwave radiation by corn and account for the greenhouse effect caused by glazing materials. The performance of the dryer was simulated at fair and overcast weather conditions. The model allowed visualization of temperature, humidity, and air velocity profiles in the dryer. The model was validated with experimental results, which showed an overprediction of temperature (8.5%) and humidity (21.4%). The experimental humidity profile suggests that there was stagnation in the airflow of the dryer, which was accurately predicted by the model. The model was used to simulate the dryer’s performance under overcast conditions, and the predicted moisture removal was 32% less than the simulated fair-weather case. [ABSTRACT FROM AUTHOR]

The world is moving towards the reduction of dependency on fossil fuels. Various innovations are undergoing to make the use of sources of renewable energy like wind, solar, tidal etc. Among these sources, solar energy is available in enormous quantity and best option that may be used for space heating and generation of electric energy. For drying agricultural and non-agricultural products, solar energy can be used directly or indirectly. But in open sun drying the products are affected by external calamities such as rain, insects and animals. To overcome the shortcomings of open sun drying various greenhouse solar dryer had been proposed so far. Some of recent researches have been discussed in the paper. This paper provides the data of already developed greenhouses so the reader can develop new and modified the greenhouse structure. To accomplish this, various researches of recent years have been studied and presented in this review. [ABSTRACT FROM AUTHOR]