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This experimental study aimed to evaluate the efficacy of natural and forced convective drying techniques in reducing the moisture content of the grapes in comparison with the conventional open sun drying method. Moisture effective diffusivity and activation energy were graphically determined using the Arrhenius equation. In the initial three-day period, forced convection drying significantly reduced moisture from 2000 g to 353 g, with a minimum loss of 14 g. In the next three days, natural convection reduced moisture from 2787 g to 468 g, with a minimum loss of 11 g. These outcomes were then compared to the results of open-sun drying. The investigation showed that open drying and natural convection methods eliminated 25.05 % and 82.35 % of the moisture content, respectively. However, for three days, open-sun drying removed 30.5 % of grape moisture, while forced convection achieved an impressive 83.21 % reduction. The study's innovative mathematical model explained drying curve characteristics, supported by correlation coefficients and parity plots. The comparison shows that the experimental moisture ratios and those predicted by the new correlation exhibit R2 values ranging from 0.984 to 0.994. [ABSTRACT FROM AUTHOR]

Exergoeconomic analysis is one of the basic methods that clearly reveal the energy cost analysis of a system. The analysis of environmental impact, on the other hand, is the based factor that detects energy payback time and CO 2 reduction according to the amount of energy contained in a system. In this study, a wind energy assisted hybrid solar dryer (WASD) was developed, tested in both simple conventional solar dryer (CSD) and WASD modes, and exergoeconomic and environmental impact assessments were examined for these two modes. While the required electrical energy for the WASD mode was obtained from the wind energy, on the other hand, the necessary electrical energy for the CSD mode was required from the grid electricity. According to the exergoeconomic analysis results, it was detected that the fan was the basic component that needed improvement in both situations. With respect to the environmental impact analysis, the energy payback periods for WASD and CSD modes were determined as 1.36 and 0.62 years, respectively. Moreover, the data obtained revealed that the WASD mode was approximately 50% more advantageous in terms of energy and drying efficiency compared to the CSD mode. [ABSTRACT FROM AUTHOR]

In this study, energy, exergy and sustainability analysis of the solar and wind energy assisted hybrid drying system were discussed. The drying process was carried out by solar dryer. Wind energy was used to provide the electrical energy required for the operation of the fan in the drying unit. So, no external energy source was required for the drying process. The main purpose of the study was to contribute to the development of an economical and environmentally friendly drying system that was operated using only two different renewable energy sources. The drying characteristics of banana slices were determined in the experiments. It was found that the exergy efficiency of the dryer was in the range of 68.04–83.89%, as a result of the experiments. The system was also examined in terms of waste exergy rate, improvement potential and environmental sustainability. The evaluations showed that the hybrid dryer had 57.7% and 21.52% higher exergy efficiency compared to other conventional solar dryers and solar assisted- hybrid dryers, respectively. Moreover, the energy payback period was determined as 1.36 years. This result clearly indicated that the system can recover the energy it consumed in approximately 38.18% shorter time compared to other solar dryers. [ABSTRACT FROM AUTHOR]

In this study, the design, development, and performance analysis of novel thermal energy storage integrated evacuated tube heat pipe solar dryer was investigated. A new common condenser heat pipe system having thermal energy storage was incorporated into the solar collector of the dryer. Therminol 55 was used as the thermal storage medium. The performance analysis was carried out with air mass flow rates between 0.003 kg/s to 0.02 kg/s and a combination of two mass flow rates 0.015 kg/s and 0.0065 kg/s. The maximum outlet temperature of the air delivered by the solar collector during the study was 118 °C. The average energy and exergy efficiency of the solar collector varied between 10%-30% and 1.9%-5.6% respectively. Agricultural products like tomatoes and carrots were dried in the dryer. The effect of moisture diffusivity variation for tomatoes and carrots with the mass flow rate of air and product thickness was analyzed in this study. The Newton model fairly demonstrated the solar drying characteristics of tomatoes. The combined mass flow rate method increased the average collector outlet temperature to 67 °C against 56 °C during a single mass flow rate and decreased the drying time by 2 h. The payback period for the dryer was 2.6 years. [Display omitted] • Novel thermal storage integrated evacuated tube heat pipe based solar dryer. • Suitable for drying applications with wide range of temperatures. • A new common condenser heat pipe arrangement for thermal storage. • High-temperature air was obtained even during off sunshine hours. • The solar dryer is an economic and environment-friendly one. [ABSTRACT FROM AUTHOR]

Solar drying has received great interest as a viable alternative solution to fossil fuel dryers. However, due to the intermittency of the solar resource, solar dryers suffer from discontinued drying and thus, long drying time. In this paper, the use of sorption materials to enhance the performance of solar dryers is reviewed. The main aspects regarding their use as thermal energy storage or dehumidification materials are highlighted. The paper shows that solid adsorbents, especially silica gel, are the most used materials. The use of composite materials, for instance the mixture of bentonite, CaCl 2 , vermiculite, and cement proved to be promising. The incorporation of a sorption dehumidifier in a solar dryer, usually at the solar collector inlet, generally leads to a reduction of the drying time of 15–30%, although values up to 50% and even 64% have been reported. On the other hand, introducing sorption materials as thermal storage in a solar dryer, mostly integrated at the top in the drying chamber, usually leads to a reduction of the drying time in a range of 30–45%. There are still various aspects to be investigated in depth before a large-scale utilization of these techniques in solar drying technology. [Display omitted] • Sorption materials are used as dehumidifiers or thermal storage in solar dryers. • Sorbent-based dehumidifiers or thermal storages enhance solar dryers'performance. • Typical drying time reduction compared to operation without sorption storage: 30–45%. • Silica gel is the most popular sorption material in solar dryers. • Solid sorption materials are more used than liquid ones as they are easier to handle. [ABSTRACT FROM AUTHOR]

Solar energy as a clean energy source is widely investigated to find out the effective mechanisms to meet a large part of energy demand in the near future. In the present research, a square-spiral finned quadruple-flow solar collector assisted dryer has been designed, and numerically compared with finless collector. Main aim of the current work is to develop and analyze a sustainable solar drying system. In this study, different from similar works, heat transfer surface area has been enhanced by using square-spiral geometry which is an unconventional fin type. According to the numerical findings, a finned quadruple-flow collector which found more efficient has been manufactured, integrated with a drying chamber and performance experiments have been conducted. In the manufactured solar dryer, a PV panel has been used to run utilized fan. CFD simulation and empirical outcomes of this research exhibited the successful design of finned quadruple-flow collector. Experimentally obtained average efficiency of quadruple-flow collector varied in the range of 73.27–78.19%. Also, mean exergy efficiency of drying chamber was found between 44.16 and 58.38%. Sustainability index and waste exergy ratio values as important factors were attained between the ranges of 1.93–2.73 and 0.52–0.56, respectively. [Display omitted] • Design of a quadruple-flow PV-driven indirect solar dryer. • Experimental and CFD analysis of a quadruple-flow solar air collector. • Mean exergy efficiency of the drying chamber varied between 44.16-58.38%. • Sustainability index value was obtained in the range of 1.93-2.73. [ABSTRACT FROM AUTHOR]

In this study, the manufacturing and testing of an infrared dryer equipped with a PV/T solar collector were investigated. The total energy for the drying process is provided by solar energy. This study sought to compare the experimental results of glazed and unglazed modes and observe the effect of volume flow rate variations on the drying process of the products to determine the dryer's energy and exergy efficiency and analyze the drying kinetic of potato slices. The amount of inlet airflow to the PV/T was controlled during the experiment. The power of the fan is supplied directly from two photovoltaic panels and the surplus amount of electrical energy is assigned to an infrared radiation source to enhance the process. Despite the low energy consumption of the current system, the products' drying time was significantly reduced compared to similar systems. As a result, in glazed experiments, the drying time is prolonged in a range of 12–25% for 3 mm thicknesses and between 5 and 25% for 7 mm thicknesses compared to unglazed experiments. The maximum system energy efficiency and system exergy efficiency were 9% and 0.5%, respectively, calculated for 7 mm slices in unglazed tests. • An infrared dryer equipped with a PV/T air collector was designed and tested. • Effect of glazing PV/T collector on the drying process was demonstrated. • Energy and exergy analysis were conducted for potato drying process. • Glazing increased drying time and chamber temperature up to 25% and 7 °C. • Radiant power decreased by 20–30% in glazed mode compared to unglazed mode. [ABSTRACT FROM AUTHOR]

The main aim of this study was to develop an integrated solar-tracking system to maximize the efficiency of solar heaters manufactured from recyclable aluminum cans (RAC) for optimum drying of apple slices. The results revealed that the thermal efficiency of the solar air heater incorporated with a tracking unit was significantly improved by about 45% compared with the conventional fixed heaters at all tested air flow rates. The highest thermal efficiency of 87.1% of the solar air heater equipped with a tracking unit was achieved at the highest air flow rate of 44 m3 h-1. The effective moisture diffusivity (D eff) increased at the high levels of drying air temperature and flow rate and the highest value of D eff (5.43 × 10−10 m2s−1) was obtained in the dryer with a tracking system at the highest air flow rate of 44 m3 h-1. The drying rate of apple slices under such a tracking module was considerably higher than that of either the traditional fixed system or the ambient sun drying. • Integrated solar tracking system was develop to maximize the efficiency of solar air heaters. • Two solar dryers were constructed and examined for drying apple slices. • Thermal efficiency of solar air heater improved by 45% using the tracking module. • Increasing the air flow rate increased the thermal efficiency and the drying rate. • Drying rate of apple slices was higher for tracking system than fixed system and ambient drying. [ABSTRACT FROM AUTHOR]

The present work focuses on drying of Garcinia pedunculata in an efficiently developed free convection corrugated solar dryer (FCCSD) and conventional open sun. The experimental solar drying results for two batches are presented. The moisture contents of Garcinia pedunculata in the dryer was reduced to 7.22% (wb) for the first batch and 7.1% (wb) for the second batch in 28 h from the initial of 88% (wb) of moisture content. Moisture content was reduced to 10.18% (wb) and 10.08% (wb) for the first and second batches respectively in 55 h in open sun drying. Midilli and Kucuk model was found the most suitable for drying process in the developed solar dryer. Two-Term model was suitable for open sun drying. The average thermal efficiencies of the solar dryer for the first and second batches were evaluated as 33.29% and 33.45% respectively. The average specific energy requirement and average thermal efficiency of the FCCSD were estimated as 68.00 kWhkg−1 and 10.69% for the first batch 65.54 kWhkg−1 and 10.77% respectively for the second batch. For the newly developed FCCSD, the payback period was estimated as 0.6 year. • A free convection corrugated solar dryer was developed. • Garcinia pedunculata (GP) was dried in two batches. • Drying in the solar dryer took 27 h less than the one sun drying. • The average dryer efficiencies were 10.69% and 10.77% for the first and second batches. • The payback period from the economic analysis of the solar dryer was 0.6 year. [ABSTRACT FROM AUTHOR]

The paper presents an active mix-mode wind-powered fan solar dryer (AWPFS) with a passive mix-mode non-wind-powered solar dryer (PNWPS) evaluated with pre-treated potato slices. The two dryers were tested with and without glycerol as thermal energy storage. The objective was to present a non-electricity powered active solar dryer using only clean energy sources. Evaluation of the dryer took place at ambient temperature range of 24–50 °C and humidity of 10–52%. The results indicate that drying with AWPFS integrated with glycerol showed shorter drying time than drying with AWPFS only or PNWPS. Dipping the potato in a salt solution and blanching for 30 s before drying quickened the drying rate of the potato compared to other treatments. The energy consumed for drying ranged from 4.10 to 4.98 MJ, while the specific energy consumption ranged from 2.846 to 3.686 kWh/kg. The drying efficiencies ranged from 25.031% to 31.5%, while the exergy efficiency ranged from 14.5 to 80.9%. With low electricity penetration density across Africa, this dryer with naturally powered fan will help crop processors dry their product faster and about 15.3–290.4 $/year could be saved at 10–100% rate of usage • First time energy and exergy of solar dryer with wind generator power fan source and glycerol as heat storage were studied. • Drying with the combination of wind generator and thermal storage proved more energy effective. • Glycerol has positive effect on the drying time but increased energy consumption. • About 15.3–290.4 $/year could be saved at a rate of usage of 10–100% if the solar dryers are adopted. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to accelerate the drying process of black ginger in a forced convection mixed mode horizontal solar dryer (FCMHSD) by using two successive air mass flow rates. When the drying rate attains the falling rate period, air mass flow rate has minimal effect on drying rate. To diffuse bound moisture present in the product, air mass flow rate has to be reduced for raising the air temperature in the solar dryer. In this manuscript, two cases were considered for drying; Case – 1 with constant air mass flow rate of 0.062 kg/s and Case – 2 with two successive air mass flow rates of 0.062 kg/s during the initial period of drying and 0.018 kg/s during the falling rate period. The performance of FCMHSD was evaluated in terms of drying time, drying efficiency, specific energy consumption (SEC) and moisture diffusivity. The estimated SECs for Case – 1 and Case – 2 were 1.07 kWh/kg and 0.56 kWh/kg, respectively. A significant improvement in thermal performance and moisture diffusivity were observed when the FCMHSD operated under Case – 2 than under Case – 1. The use of two successive air mass flow rate is a new approach for accelerating the drying process. • A new approach in solar drying of black ginger is proposed. • Higher flow rate in initial and lower flow rate in the falling rate period were used. • Case-2 accelerates the drying process and reduces the energy consumption by 50%. • Quality of solar dried black ginger is higher than open sun dried sample. [ABSTRACT FROM AUTHOR]

The study was aimed at design and development of an energy efficient solar dryer suitable for continuous drying operation. In this dryer, water was used as a thermal energy storage and heat transfer medium, and air as an intermediate fluid. The major parts of the dryer were flat-plate solar water collector, water storage tank, drying chamber, heat exchanger, and liquefied petroleum gas (LPG) water heater. The dryer was designed to work mostly on solar energy during peak sunshine hours and LPG water heater as auxiliary heat source during low sunshine hours. The performance of the developed solar-LPG hybrid dryer was evaluated using shrimps (Metapenaeus dobsoni). The moisture content of fresh shrimp was reduced from 76.71% (w.b) to 15.38% (w.b) within 6 h of drying. The drying rate curve showed that shrimp drying occurred under falling-rate drying period. Results revealed that the water was capable of capturing maximum heat energy during peak sunshine hours. The maximum collector outlet temperature of 73.5 °C was obtained during drying. Overall, solar system supplied 73.93% of heat energy and LPG water heater assisted rest of the energy requirement due to lower incident solar radiation during start and end of drying. The maximum collector and drying efficiency obtained for shrimp drying were 42.37% and 37.09%, respectively. • Water as a thermal energy storage medium stored maximum heat energy as sensible heat during sunshine hours. • Obtained maximum solar collector water outlet temperature of 73.5 °C at 01:30 p.m. during shrimp drying. • Solar system supplied 73.93% of the energy requirement of the solar-LPG hybrid dryer for shrimp drying. • The maximum collector and drying efficiency obtained were 42.37% and 37.09%, respectively. [ABSTRACT FROM AUTHOR]

Drying is a process of hydration and Elimination of water which allows the proliferation of microorganisms and development of chemical reactions without influencing morphological structure of Food Material. This paper focused on the influence of temperature on drying kinetics of the Mediterranean mussels (mytilus galloprovincilis) as per the requirement for storage seafood. Convective drying kinetics and hygroscopic behavior of Mytilus Galloprovincilis was carried out in a solar dryer operating in forced convection. Experimental drying kinetics were measured at three air temperatures (50, 60, and 70 °C), and two air flow rates fixed at (300 and 150 m3 h−1) with ambient air temperature in the range of 36–42 ± 1 °C, 8.92 to 18.86 ± 2% for ambient humidity, 422 to 988 w/m2 for solar irradiation. Experimental data of drying are collected to plot the characteristic drying curve. Nine mathematical models available in the literature are used for describing the drying curves. The logarithmic model showed the best fitting of experimental data with a highest value of correlation coefficient (r), and lowest value of reduced chi-square (χ2). Effective diffusion coefficient value D eff was obtained between 1.14 10−9 to 3.61 10−9m2s−1 based on the Fick equation. • Convective solar dryer was used to valorize drying of Mytilus Galloprovincilis. • Drying kinetics of mussels is influenced by the drying air temperature. • Logarithmic model is the most appropriate for describing the drying curves. • Effective moisture diffusivity values ranged from 1.14 10−9 to 3.61 10−9 m2s−1. • Activation energy expressed the effect of temperature on the diffusion coefficient. [ABSTRACT FROM AUTHOR]

Wood drying is an important operation in many sectors, and harnessing solar energy for this purpose has received a lot of interest due to its sustainability and cost-effectiveness. In this work, we compare how two solar collector configurations namely, Flat Plate Collector and Photovoltaic Thermal collector, perform in a solar wood drying system. The moisture content of wood was reduced from 73% to 12% in four different regions: Errachidia, Meknes, Tangier, and Rabat. The Gauss–Seidel method is used to solve the governing equations for heat transfer after discretizing them via implicit finite differences. The effectiveness of the solar collectors was simulated through the TRNSYS software, and a numerical program was generated using the Python programming language. According to our research, the FPC beats the PVT collector because of its higher output temperatures dramatically shorten the time it takes for wood to dry. The study emphasizes how temperature and humidity affect drying, showing that faster drying occurs in hotter, drier locations. Furthermore, drying time can be saved by using FPC and PVT collectors compared to conventional open sun drying. The primary conclusions of this research are: In the FPC solar dryer, the drying time needed in Errachidia, Meknes, Rabat and Tangier was 144 h, 162 h and 171 h, respectively. While in the PVT solar dryer, it required 162 h in Errachidia, 171 h in Meknes, 180 h in Rabat and 189 h in Tangier. Further, the FPC collectors showed a range of 293 K to 347 K for the outlet temperature. The PVT collectors, however, showed a variable range between 295.9 K and 320 K. The drying periods and temperature ranges examined revealed that Errachidia was the most advantageous location, regardless of whether FPC or PVT collectors were used. In fact, the drying time that can be saved by using FPC is 41% while PVT is 31% compared to traditional open sun drying. • The moisture content of wood was reduced from 73% to 12% in four different regions. • Effect of temperature, humidity, and wood thickness on the drying of wood was highlighted by the study. • Comparative analysis of FPC and PVT solar collectors under four different climates. • Simulation conducted using TRNSYS software and Python programming language. • Study highlights the potential of PVT collectors for combined electricity generation and thermal energy production. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a solar cabinet drying system equipped with a heat pipe evacuated tube solar collector (ETSC) and thermal storage system with application of PCM. The thermal analysis of the solar collector, drying efficiency, CFD modeling of the system and quality evaluation of dried apple slices was considered. The performance of the dryer was simulated and validated by experimental data. The experiments was conducted at three air flow rates (0.025, 0.05 and 0.09 kg/s) for the drying system with and without using PCM for drying apple slices with the thickness of 5 mm. The result of thermal analysis showed that using PCM increases the input thermal energy about 1.72% and 5.12% for the air flow rates of 0.025 and 0.05 kg/s respectively, but excessive increase in air flow rate (up to 0.05 kg/s) decreases input thermal energy. The maximum overall drying efficiency was related to the system with PCM at the air flow rate of 0.025 kg/s and it was 39.9%. CFD simulation of the storage system and the dryer showed that there is a good agreement between the simulated and experimental. Using PCM has no adverse effect on the quality of the dried product. • The performance of a solar cabinet drying system equipped with ESTC simulated and developed. • Effect of using PCM on thermal and drying efficiency and drying kinetics of apple slices evaluated. • Using PCM as thermal energy saver shortened drying time in the range of 9.37%–10.02%. • Using PCM accelerated the drying process along the night time. • The quality of the dried apple slices was not affected negatively by using PCM. [ABSTRACT FROM AUTHOR]

A numerical model has been proposed in this work for predicting the energy performance of a heat pump assisted solar dryer under continental climates. The model is based on energy and mass balance. The energy performance comparison between heat pump dryer, solar dryer and heat pump assisted solar dryer are presented. The simulation was performed for four different climatic conditions of Almaty city in Kazakhstan. The simulation results showed that, the heat pump assisted solar dryer is more energy efficient when compared to the conventional solar dryers. It is also confirmed that, the conventional solar dryers are not suitable for continental climatic conditions having low ambient temperatures. The heat pump dryer reduces the initial moisture content of banana (on wet basis) from about 74% to the final moisture content (on wet basis) of about 19% in 21 h. Similarly, the solar dryer reduces the initial moisture content (wet basis) from about 74% to the final moisture content (wet basis) of about 20% in 35 h. The specific moisture extraction rate and coefficient of performance of a heat pump assisted solar dryer are estimated to be about 0.6 kg/kWh and 2.72, respectively. • HPASD requires 21 h to attain final moisture content (on wet basis) of 20%. • SMER of HPASD is 0.6 kg/kWh. • The COP of HPSAD is 2.72. • Quality of dryed produces in HPASD is good compared to other drying methods. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

In this study, the performance of a forced convection mixed-mode solar dryer with thermal energy storage is experimentally analyzed. The main goal was to develop an efficient and cost effective dryer that maintains drying process after sunset. The dryer mainly consists of a solar collector/absorber, drying chamber and a fan. A photovoltaic panel and battery storage are also integrated with the dryer to supply the required electrical energy. The experiments are carried out to dry fresh apricot slices at different working conditions. The effect of using phase change material to store thermal energy during daytime is analyzed. It is concluded that the performance of the solar collector is improved and the drying process is effectively extended when solar energy was not available. It is also observed that the rate of drying is almost constant along the drying chamber. The moisture pick-up efficiency and the overall thermal efficiency of the dryer are about 10% and 11%, respectively. [ABSTRACT FROM AUTHOR]

The current study designed, constructed and experimentally evaluated a heat-pipe evacuated tube solar dryer with heat a recovery system in which water was used as working and recovery fluid in the solar and dryer loops, respectively, and air was used as intermediate fluid in the dryer section. The heat recovery system was used to enhance the overall efficiency of the system and to make maximum use of solar energy intake of the dryer. The hot water in the storage tank, which is heated by the solar loop, is sent to the dryer, depending on the system requirement, and its heat in the heat exchanger is delivered to the blown air. The heated air enters the main chamber of dryer, where the drying products exist. This system was tested in the weather conditions of Sanandaj city and the obtained results indicated the effectiveness of heat recovery system. In volumetric flow rate of 0.0328 m 3 /s, the maximum outlet air temperature of dryer was approximately 44.3 °C. At the end of the day, the exergetic efficiency of the system reaches its maximum rate, approximately 11.7%. Using regression analysis, the most accurate equation for expressing the effectiveness of dryer was obtained. [ABSTRACT FROM AUTHOR]

The performance of a new design of a solar dryer for drying osmotically dehydrated cherry tomatoes is presented. The dryer consists of drying cabinet, heat exchanger, 16-m 2 water type solar collector, and water type heat storage unit. The cabinet size is 1.0 m wide × 3.0 m long × 1.4 m high with the load capacity of 100 kg for osmotically dehydrated cherry tomatoes. Three batches of osmotically dehydrated cherry tomatoes were dried in this dryer during May–June, 2014. For each batch, 100 kg of osmotically dehydrated cherry tomatoes were dried. There was a considerable reduction in drying time in the new solar dryer as compared to natural sun drying. The dried products were completely protected from rains and insects and were of high quality dried products. The efficiencies of the solar collector was 21%–69%. The pay-back period of the dryer is estimated to be 1.37 years. [ABSTRACT FROM AUTHOR]

A mixed mode natural convection solar crop dryer with a backup heater was designed and constructed from locally available materials and used to dry freshly prepared pineapples under four drying Scenarios for drying to correspond to specified drying periods for four typical seasons in Ghana. The experiments were devised for the material moisture content to be monitored continuously till the desired moisture content of between +106% and 184% (d.b) was achieved. In solar heating mode of operation, results show that the thermal mass was capable of storing part of the absorbed solar energy but the quantities involved are insufficient to sustain night drying. It was possible to dry a batch of pineapples in each mode of operation. The dryer reduced the moisture content of pineapple slices from about; 924% to 106% in 19 h; 1049% to 184% in 10 h; 912% to 155% in 7 h; and 1049% to 144% (d.b) in 23 h, for drying in Scenarios 1, 2, 3 and 4, respectively. The average moisture pickup efficiency values obtained were 27%, 24%, 11%, and 32% for drying in Scenarios 1, 2, 3, and 4, respectively. [ABSTRACT FROM AUTHOR]

A state-of-the-art solar crop dryer was developed with thermal energy storage to maintain continuity of drying of herbs for their colour and flavour vulnerability. The dryer consists of flat plate solar collector, packed bed phase change energy storage, drying plenum with crop trays and natural ventilation system. Dryer is designed with a maximum collector area of 1.5 m 2 , six crop trays with an effective area of 0.50 × 0.75 m 2 , can hold 12 kg of fresh leafy herbs. The dryer is attached with a packed bed thermal energy storage having capacity of 50 kg phase change material (PCM). The drying system works in such a manner that phase change material stores the thermal energy during sun shine hours and releases the latent and sensible heat after sunset, thus dryer is effectively operative for next 5–6 h. The temperature in drying chamber was observed 6 °C higher than the ambient temperature after sunshine hours till the mid night during the month of June at Jodhpur. Economic performance of the dryer was analysed with return on capital and simple payback period as 0.65 and 1.57 year respectively on optimum cost of raw material and product sale price. [ABSTRACT FROM AUTHOR]

Abstract: A large-scale solar greenhouse dryer with a loading capacity of 1000 kg of fruits or vegetables has been developed and tested at field levels. The dryer has a parabolic shape and the dryer is covered with polycarbonate sheets. The base of the dryer is a black concrete floor with an area of 7.5 × 20.0 m2. Nine DC fans powered by three 50-W solar cell modules are used to ventilate the dryer. The dryer was installed at Champasak (15.13 °N, 105.79 °E) in Lao People’s Democratic Republic (Lao PDR). It is routinely used to dry chilli, banana and coffee. To assess the experimental performances of the dryer, air temperature, air relative humidity and product moisture contents were measured. One thousand kilograms of banana with the initial moisture content of 68% (wb) was dried within 5 days, compared to 7 days required for natural sun drying with the same weather conditions. Also three hundred kilograms of chilli with the initial moisture content of 75% (wb) was dried within 3 days while the natural sun drying needed 5 days. Two hundred kilograms of coffee with the initial moisture content of 52% (wb) was dried within 2 days as compared to 4 days required for natural sun drying. The chilli, coffee and banana dried in this dryer were completely protected from insects, animals and rain. Furthermore, good quality of dried products was obtained. The payback period of the dryer is estimated to be 2.5 years. A system of partial differential equations describing heat and moisture transfer during drying of chilli, coffee and banana in the greenhouse dryer was developed. These equations were solved by using the finite different method. The simulated results agree well with the experimental data. This model can be used to provide the design data for this type of dryer in other locations. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a numerical procedure is outlined and representative results for heat and mass transfer during convective drying of porous bodies are presented. The Luikov model was implemented and applied both on individual samples of construction materials and agricultural products, as well as on a drying-chamber scale, with parallel flow of a hot air stream over rectangular slabs which represent the product to be dried. In the latter case the configuration is an experimental dryer in which the heat source is a solar air collector with evacuated tubes. A general approach was developed that allows a selection between modelling of phenomena either in the drying solid only, or considering an extended simulation domain encompassing, apart from the solid body, the flow of air as well. In the second case, the solution of the flow field is pursued along with a conjugate heat/mass transfer problem coupling the solid and fluid phenomena and in both cases phase change (evaporation) was taken into account. For the numerical simulation, the finite-volume method was used. The validation of the model was based on experimental and numerical results from the literature and results from simulations that were conducted in the pursuit of the energetic optimization of an experimental solar dryer of NCSR “Demokritos” are presented. In the latter case, the effect of the particular flow field features developing for a single and a double-plate configuration on the heat/mass transport and drying rates is demonstrated. Such a methodology could be used to analyze the transport phenomena in any type of convective dryer, including those utilizing solar energy as the heat source. [Copyright &y& Elsevier]

Abstract: A direct type natural convection solar dryer is designed. It is constructed in local materials (wood, blades of glass, metals) then tested experimentally in foodstuffs drying (cassava, bananas, mango). It is about an experimental approach which consists in analyzing the behavior of the dryer. The study relates mainly kinetics and establishment of drying heat balances. The influence of significant parameters governing heat and mass transfers, such as solar incident radiation, drying air mass flow and effectiveness, is analyzed in order to evaluate its thermal performances. Experimental data can be represented by empirical correlations of the form M(t)=Mi exp(−kt) for representation of drying process. The resolution of these drying equations makes-possible to predict total drying time of each product. Moreover, this drying process allows to reduce the moisture content of cassava and sweet banana approximately to 80% in 19 and 22h, respectively to reach the safety threshold value of 13%. This value permits the conservation of these products about one year without deterioration. The determination of parameters, like ambient temperature, drying chamber temperature, drying air mass flow and incident heat fluxes, allow to predict the drying effectiveness for modeling and refining the dimensioning of the elaborate prototype. [Copyright &y& Elsevier]

Abstract: During the last 25 years, the author has designed, constructed, studied and promoted solar oven, hybrid solar/electric oven, solar oven cum drier, solar cooker cum water heater and solar still. In different parts of the world, solar cookers have been made, studied, patented, however, their real uses are very limited due to many reasons—unstable climate, economic, cultural, social and single use, etc. In order to overcome part of the problems mainly the last one, author has recently designed one hybrid food processor (multi-purposes device) and studied various technical and practical aspects. It has been used for cooking, heating/pasteurizing water (to inactivate microbes) and distillation of small quantity of water (to remove different minerals) and drying domestic products (fruits, vegetables and condiments/herbs, etc.). For more than three years of use, author has found this to be a useful device, mainly from convenience, fuel saving, economic and also from ecological point of view. This device can be used at any time and for different uses but with the reduced consumption of conventional fuel. [Copyright &y& Elsevier]

Abstract: A solar dryer for drying herbs and spices using hot air from roof-integrated solar collectors was developed. The dryer is a bin type with a rectangular perforated floor. The bin has a dimension of 1.0m×2.0m×0.7m. Hot air is supplied to the dryer from fiberglass-covered solar collectors, which also function as the roof of a farmhouse. The total area of the solar collectors is 72m2. To investigate its performance, the dryer was used to dry four batches of rosella flowers and three batches of lemon-grasses during the year 2002–2003. The dryer can be used to dry 200kg of rosella flowers and lemon-grasses within 4 and 3 days, respectively. The products being dried in the dryer were completely protected from rains and insects and the dried products are of high quality. The solar air heater has an average daily efficiency of 35% and it performs well both as a solar collector and a roof of a farmhouse. [Copyright &y& Elsevier]

The solar dryer reported in this paper was developed to enable farmers to add value to their produce by drying it at farm itself. It can also be used in cottage industries in remote places. The dryer has a multi-shelf design with intermediate heating, passive, integral, direct/indirect and portable solar dryer. Intermediate heating of air in-between trays results in uniform drying in all the trays. Since the dryer at the farm is not likely to be used throughout the year, it has been made portable. A novel feature of this dryer is that the product can be dried under shade or otherwise as per requirement. The design is low cost to make it economically viable. The maximum stagnation temperature was 75 °C in the month of November at Ludhiana (31°N). During experiments on drying of fenugreek leaves the moisture evaporation on first, second and third drying day was 1.4, 0.9 and 0.4 kg/m2 of aperture area. To overcome the problem of reduction in efficiency on second and third drying day, a semi-continuous mode of loading has been investigated, in which the efficiency remains almost the same on all drying days. The shelf life of the dried product is more than one year. [Copyright &y& Elsevier]

This paper presents a comparison of optimized mixed-mode and indirect-mode natural convection solar dryers for maize. The mixed-mode and indirect-mode solar drying simulation models were validated against results from a laboratory solar dryer with experiments carried out under a solar simulator at the University of Newcastle upon Tyne, UK. The models are now run under variable solar conditions in order to optimize the dryers and compare their performance. The inputs to the simulation models were Zambian weather conditions and materials. The solar drying simulations are combined with the cost of the dryer materials and a search technique that finds the dryer dimensions at the minimum drying cost. Optimization gave a shorter collector length for the mixed-mode solar dryer (1.8 m) than for the indirect-mode dryer (3.34 m) of the same grain capacity (90 kg). The drying cost, annual cost and initial cost of the mixed-mode dryer are lower than those of the indirect-mode although the quantity of dry grain obtained from the mixed-mode for the whole year is less than for the indirect-mode; the drying costs are 12.76 and 16.05 US$/ton for mixed-mode and indirect-mode dryers, respectively. [Copyright &y& Elsevier]