Open Sun Drying Research Articles

Design, CFD Simulation, Prototype, and Experimental Investigation of Indirect Active Solar Dryer for Banana

Indirect active tray solar dryer was designed, CFD simulated, and constructed for the drying of banana in Addis Ababa, Ethiopia. The experimental investigation was done after the CFD ANSYS Fluent simulation of different parameters based on the uniformity temperature and air flow distributions on the symmetry plane. The performance of the designed solar dryer was compared with that of the open sun dryer method, based on drying rate, moisture ratio, and moisture content on a wet and dry basis. From fourteen different mathematical drying thin layer kinetics models, the maximum correlation coefficient of 0.999574, the minimum root mean square of 0.0001352, and the minimum reduced chi-square of 0.007353 were obtained for the Verma et al. model for the slice banana in the designed active solar dryer. Recycling the air from the outlet of the drying chamber on the first day is not possible because the quality of the air is lower when compared with ambient air. The outlet air temperature and relative humidity of the drying chamber were 4.39℃ higher and 8.24% lower than the ambient air temperature and relative humidity respectively, so it is possible to recycle the air after the first day. The average moisture content removed from the product in the designed solar dryer and open sun dryer was 68.01% and 51.01%, respectively, in the 22 and half5 drying hour. The difference between the maximum and minimum moisture removal was 4.47%. It indicates there is a uniform drying in the designed solar dryer. The overall solar air collector efficiency was 33.80%and the maximum drying efficiency was 31.10 %.

Experimental testing of mixed-mode double pass solar air heater integrated with aluminium cans for red pepper drying

A solar air heater that operates in the mixed-mode double pass and an absorber plate has aluminum cans at the top and bottom of the absorber for red pepper drying experiments was conducted in Bahir Dar, Ethiopia climatic conditions. A total dying period of red pepper in a mixed-mode solar greenhouse dryer takes less time than an open solar drying system. From the experiment, the average daily dryer chamber temperature ranges between 39.93 0C and 47.02 0C and the average daily ambient temperature ranges between 24.890C and 27.530C. Solar insolation reached 973 W/m2 when the sun was at mid-day and minimum solar insolation was 220 W/m2 and 0.0383 kg per second of air are expelled. A newly designed mixed-mode double pass, integrated with an Aluminum can dryer and the traditional open sun dryer, achieves an efficiency of 46% and 28%, respectively. In the open sun dryer system and the mixed-mode solar dryer, the drying rates are 0.0003395 kg/s and 0.0000365 kg/s respectively. On eleven mathematical models, Microsoft Excel was used to perform the statistical analysis. Logarithmic models were found to be the best explanation of red pepper behavior in both mixed-mode and open-sun solar dryer systems. These models were tested by comparing the maximum value of the coefficient of determination R2 and the minimum value of reduced chi-square X2 and root mean square error RMSE between experimental and predicted moisture ratios.

Experimental study of a novel photovoltaic-thermal-thermoelectric generator-based solar dryer for grapes drying

ABSTRACT In the present work, a novel photovoltaic-thermal-thermoelectric generator (PVT-TEG) based solar dryer has been developed, and its drying performance is experimentally investigated and compared with open sun drying (OSD). The reason for incorporating the PVT-TEG system in the solar dryer is to improve the system’s utility in practical drying applications by augmenting electrical power generation with the combination of PV and TEG along with extracting thermal energy for drying, thereby improving the overall system efficiency. Grapes drying has been performed to analyze the drying process and thermal and electrical performance of the system. The moisture content level after the experiment is evaluated as 1.71 (d.b.) from an initial value of 4.00 (d.b.) in PVT-TEG solar drying compared with 2.51 (d.b.) in OSD. The findings of the drying performance are determined as 17.81% for drying efficiency, 1.10 kWh/kg for specific energy consumption, and 0.68 kg/kWh for specific moisture extraction rate. The energy efficiencies obtained for the experiment are PV panel efficiency of 14.07%, TEG efficiency of 11.64%, PVT efficiency of 72.36%, and thermal efficiency of 48.50%. When compared to the open literature, the utility of the present novel dryer is found in terms of its enhanced drying and energy performances.

Development of infrared-assisted hybrid solar dryer for drying pineapple slices: Investigation of drying characteristics, mass transfer parameters, and quality attributes

The research aims to the development and performance evaluation of an infrared-assisted hybrid solar dryer (IR-HSD) for drying pineapple slices. The IR-HSD contains an evacuated tube solar collector, blower assembly, drying chamber, infrared heater, phase change material (PCM) chamber, etc. The study investigates and compares the thermal profiling, drying kinetics, mass transfer parameters and quality attributes of pineapple slices dried using different methods, such as direct drying, phase change material (PCM)-assisted drying, PCM + IR-assisted drying, and sun drying. The average temperatures achieved inside the drying chamber for direct drying and PCM-assisted drying were 60.16 °C and 57.29 °C, respectively, while the temperature reached 60 °C for PCM + IR assisted drying. The average drying rate in PCM + IR drying was higher than in direct and PCM-assisted drying methods. The best-fitting models were the Modified Page model for direct and PCM + IR-assisted drying and the Midilli-Kucuk model for PCM-assisted and sun drying. The higher effective moisture diffusivity for PCM + IR-assisted drying was 2.59 × 10−9 m2/s, followed by direct and PCM-assisted drying. Similarly, the convective mass transfer coefficient obtained was 1.085 × 10−7 m/s, 8.321 × 10−8 m/s, and 1.381 × 10−7 m/s for direct, PCM-assisted, and PCM + IR-assisted drying, respectively. The superior quality attributes such as total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activity were observed in all drying approaches with retention of colour except open sun drying, which decreased significantly. FTIR spectroscopy analysis confirmed the presence of different bioactive, including aromatic compounds, phenols and hydrocarbon functional groups. The infrared-assisted hybrid solar drying of pineapple slices showed a better drying process and quality attributes.

Comparative Overview of Performance of the Dryers with a Conventional Method of Drying i.e., Open Sun Drying

Since ancient times, conventional techniques of food drying, such as sun drying, have been used. Currently, drying methods have been developed with the latest technology to reduce the damages caused by biochemical changes, which decrease nutritional value during the drying process. Some of the typical drying methods used for food products are sun drying, solar tunnel dryer, cabinet-type solar drying, etc. While this is going on, cutting-edge technology is being created to combine several drying techniques to produce the optimum outcomes. The most recent drying techniques used in food processing technology will be covered in this study.

Design, development, and testing of rice-husk fueled mixed-flow rice dryer for small-scale rice producer farmers

In underdeveloped nations, rice is frequently harvested at a relatively high moisture content and then dried under the open sun to a storage moisture content. However, direct UV exposure, rain, dust, premature drying, contamination, and open sun drying are all associated with problems like poor grains, discolorations, and cracking. Commercial mechanical dryer utilization is not practical in remote regions due to the absence of electrical service, high startup costs, and ongoing operating expenses. In this work, a pilot mixed-flow rice drier that ran on rice husk energy and solar energy to power the driving fan was designed, produced, and tested. The major parts of the dryer assembly that were conceived and created were the combustion chamber, heat exchanger, and mixed-flow dryer. The results of the trial revealed that the combustion chamber's average temperature was 347.3 °C, the drying air at the heat exchanger output, where the drying chamber was attached, was 63.3 °C, and the combustion chamber and heat exchanger's respective efficiencies were 52.4% and 14.9%. The mixed-flow dryer powered by rice has a significantly lower operating cost than a comparable dryer powered by electricity, petrol, and diesel. The study makes it evident that such a reasonably priced and effective rice dryer might significantly help small-scale rice producers to extend the storage duration and maintain the quality of their product.

Evaluation of Drying Behaviour of Cassava Chips under Open Sun and Oven Drying Technologies

Evaluation of Drying Behaviour of Cassava Chips under Open Sun and Oven Drying Technologies

An Empirical Study on Convective Drying of Ginger Rhizomes Leveraging Environmental Stress Chambers and Linear Heat Conduction Methodology

This comprehensive study provides an in-depth examination of the convective drying process and drying kinetics of ginger rhizomes (Zingiber officinale), precisely honing in on the influence of moisture content variation on the thermal property of thermal conductivity. Our research reveals a direct correlation between decreasing moisture content and thermal conductivity during drying, conducted under meticulously controlled conditions with a drying temperature range of 10 °C to 60 °C and an optimum drying temperature identified at 60 °C with a relative humidity of 35%. We scrutinise the thermal properties, namely, the thermal conductivity, in relation to moisture content, shedding light on the intricate dynamics involved. The study uncovers the distinct advantage of convective drying over traditional methods, shortening the drying time to just 24 h, compared to the nine and eight days required for open sun and solar tunnel drying, respectively. We identified optimal moisture levels for various ginger types: unblanched (6.63%, thermal conductivity 0.0553 W/m·K), blanched (9.04%, thermal conductivity 0.0516 W/m·K), peeled (8.56%, thermal conductivity 0.0483 W/m·K), and unpeeled ginger (5.98%, thermal conductivity 0.0460 W/m·K). As drying progressed, the moisture content fell from 81% to approximately 6–9%, concomitantly lowering the thermal conductivity from roughly 0.0553 W/m·K to around 0.0460–0.0516 W/m·K. These findings offer significant implications for the food industry, proposing improvements in drying processes and strategies for energy conservation when drying ginger rhizomes and similar agricultural produce. Moreover, this study sets a solid foundation for future investigations into potential applications of these insights to other agricultural products and various drying techniques.

Comparative Study between Open-direct Sun and Solar Drying of Onion Slices (Allium cepa L.)

Thin layer drying of onion slices (Allium et al.) was experimentally investigated using a free convective solar dryer and open-direct sun. The objective of this study is to compare the two methods of drying onions. The data of sample weight for open-direct sun and solar drying experiments were hourly recorded, drying rate (g water/100 g DM) and moisture contents (%) in dry basis (d,b) and wet basis (w,b) were calculated. Quality analysis for protein, fats, fiber, ash, and carbohydrates contents was also analyzed and evaluated. According to the results, direct open sun drying of onion slices took (19 hours) with a final moisture content of 16% and 13.5% dry basis and wet basis, respectively. At the same time, solar drying took (32 hours) with a final moisture content of 10% and 9.08% dry basis and wet basis, respectively. Solar drying showed a high drying rate as compared with direct sun drying. However, the two drying methods have a high drying rate at noon. The drying experiments showed no constant rate period but a falling rate period. For quality assessments or evaluation of onion slices, onion dried with the direct open sun was very dirty and contaminated with some foreign materials and microorganisms, while onion dried with solar showed no contamination. For quality evaluation analysis of protein, ash, fat, fiber, and carbohydrates contents, these constituents showed an increase for boss solar and direct open sun drying of onion. This is because drying reduces the moisture content of the product significantly; therefore, the dry matter was increased as a percentage.

Open Sun Drying of Beetroot Slices and its Quality Evaluation

Open Sun Drying of Beetroot Slices and its Quality Evaluation

Drying parameters of wild lettuce (Lactuca taraxaxifolia L) affected by different drying methods

This study focused on the effect of drying method on drying properties of wild lettuce leaves. The fresh wild lettuce was washed thoroughly to remove extraneous parts and subjected to pretreatments by dipping 200 g of vegetable samples into the water (1.5w/v) solution with 0.3% sodium metabisulphite held at room temperature. The pre-treated and untreated leaves were weighed and loaded in stainless steel tray and subjected to drying under cabinet dryer, open-sun drying and solar dryer. The wild lettuce drying curve exhibits a gentle downward curve, i.e. a high moisture loss at the early period of drying for all the drying methods used. The effective moisture diffusivity and activation energy were determined. The effective moisture diffusivity increased with the increase in temperature of drying. This study showed that post harvest losses of wild letuce can be minimized through drying, using mechnical devices or open sun drying, which is one of the oldest preservation processes available to the mankind.

Thermal performance of a hybrid solar dryer through experimental and CFD investigation

AbstractSolar drying comes under clean energy technology that aims to dry food products hygienically. The present work discusses the development of an energy‐efficient and cost‐effective hybrid‐type solar dryer for drying 15 kg of food products. Experiments and CFD modeling of the solar drying system have been carried out for drying tomato slices. The maximum efficiency of the collector has been obtained as 74.1% and 66.96%, respectively with and without using exhaust hot air recirculation. Performance indicators such as convective heat transfer coefficient, overall loss coefficient, drying efficiency, and collector efficiency factor have been obtained as 7.743685 W/m2°C, 5.94189 W/m2°C, 32.89%, and 0.987%, respectively. The coefficient of determination (R2) is calculated as 0.9863, 0.9919, and 0.9755 for the first, second, and third day, respectively, representing a higher order of fit of getting a performance evaluation of the collector. A p‐value is obtained as 0.49375 (>0.05) from a paired sample t‐test signifying no statistical significance difference between the predicted and actual experimental results of collector efficiency. For a constant mass flow rate of air, the maximum temperature inside the drying chamber and wall radiative heat flux obtained from experiments and CFD simulation are in good agreement, thus satisfying the validation. Further, the dryer can be used during the night time by using an electric coil producing a satisfactory drying effect. It is lightweight and easily portable to capture maximum solar radiation.Practical applicationsThe present solar dryer is most suitable for drying applications in food processing industries due to the clean and hygienic process of drying. It is easily portable to any location to capture maximum solar radiation. It is lightweight and has low construction, and maintenance costs. It is the most efficient and fast drying compared to open sun drying and can be used for large‐scale drying in industrial applications. The present study is about CFD simulations of the solar dryers for drying 5 kg of tomato slices. The drying efficiency has been increased by utilizing exhaust hot air circulation. Both the simulation and experimental results have been validated and further dryer has been used during night time by using an auxiliary heating element.

Heat and Mass Transfer, Quality, Performance Analysis, and Modeling of Thin Layer Drying Kinetics of Banana Slices

Abstract In this study, experimental works were carried out in three different drying methods named heat exchanger-evacuated tube-assisted drying system (HE-ETADS), greenhouse solar dryer (GHSD), and open sun drying (OSD) to compare thin-layer drying kinetics, concept of mass transfer, and quality assessment of banana slices. Initial moisture content (MC) of banana slices was obtained as 78 ± 2.0% (wb), which decreased to 23.2 ± 2.0% (wb), 25.6 ± 2.0% (wb), and 28.8 ± 2.0% (wb) in all three drying systems, respectively, in 9 h of drying time. Average drying rate was evaluated as 7.89, 7.65, and 7.25 g water/g solid h in HE-ETADS, GHSD, and OSD, respectively. Weibull model (WM) defines thin-layer drying kinetics of banana slices in all three drying processes. Maximum hardness and shrinkage factor of dried banana slices were obtained as 373.6 g and 75%, respectively, in HE-ETADS. Effective moisture diffusivity, activation energy, and mass transfer coefficient were computed as 1.11–2.48 × 10−07 m2 s−1, 30.25 kJ/mole, and 3.21–1.0 × 10−04 m/s, in HE-ETADS. Similarly, in GHSD and OSD, these factors were observed as 1.21–2.34 × 10−07 m2 s−1, 41.25 kJ/mole, 3.15–1.0 × 10−04 m/s and 1.3–2.21 × 10−07 m2 s−1, 56.89 kJ/mole, 3.01–1.0 × 10−04 m/s. Maximum total color changes were noted in OSD. Hence, HE-ETADS can potentially dry high moisture content crops effectively within a minimum drying period.

Quality Improvement of Dried Anchovies at Three Solar Drying Methods

Fish drying is one of the traditional methods where the fishermen land their catch on the beaches for drying traditionally under sun for several days. Dried fish provides valuable and economical sources of animal protein. The quality of dried fish is significantly influenced by the presence of microorganisms. Therefore, this study aims to determine the physical quality changes in anchovy under three different solar drying methods which are open sun drying (OSD), solar greenhouse tunnel dryer (GTD), and forced convective solar dryer (FCD) and to verify the chemical and microbial contamination in solar-dried anchovy. About (20 kg) of fresh anchovy were taken for experiments. Quality analyses were conducted in the samples before, during, and after drying. The parameters analyzed included three main analyses which are physical, chemical, and microbial analyses. The drying rate was higher in GTD compared to the two other methods. Moisture content, drying rate, and moisture ratio were significantly affected by drying methods. GTD required less time (6 hr) to dry anchovies compared to other drying methods (9 hr time). The highest reduction in lightness is in GTD dried anchovies followed by FCD and OSD. The drying methods and drying time statistically affect the lightness (L) of dried anchovies ( p ≤ 0.05 ). The water activity of solar-dried anchovies was 0.3. Experimentally dried anchovies were found to have lower microbial count compared to the dried fish quality standards. The total viable count (TVC) in fresh anchovy was 6.44 log CFU/g compared to the greenhouse tunnel dryer 2.90 log CFU/g, open sun dryer 4.16 log CFU/g, and forced convective dryer 4.19 log CFU/g anchovies. Water activity and moisture content did not affect total viable count (TVC) significantly, but it affects total fungal count (TFC) ( p ≤ 0.05 ). There was a significant difference on Krusal Wallis between the samples of three methods of drying and a fresh one on the water activity, ash content, and fat content ( p ≤ 0.05 ).

Performance evaluation of indirect type domestic hybrid solar dryer for tomato drying: Thermal, embodied, economical and quality analysis

This study evaluated the performance of an indirect type domestic hybrid solar dryer (ITDHSD) for drying tomato flakes in terms of thermal, environmental, economical, and quality parameters. The dryer achieved a final moisture content of 9% (wb) in 10 h during November 2021. Average heat utlisation factor and coefficient of performance during experimentation for drying system were 0.67 and 0.33 respectively. Embodied energy during dryer fabrication was estimated as 1434.176 kWh. Energy payback time, total CO2 mitigation, and earned carbon credit for tomato drying in dryer were projected as 4.21 years, 12.28 Tonnes, and US$364. Initial capital cost for drying system fabrication was US$245. The drying system can pay back all initial costs in 6 months of operation as estimated for tomato flakes drying. Moreover, quality of dried tomato flakes in dryer and open sun drying was estimated and compared. Indirect type domestic hybrid solar dryer provided better quality dried tomato flakes than open sun drying method as estimated from sensory analysis, rehydration ratio, shrinkage and hardness test. Further, present system was duly compared and found superior among several existing solar drying systems in terms of drying efficiency and total CO2 mitigation. The significance of the system performance lies in its potential to provide an economical, efficient, and environmentally friendly alternative to traditional drying methods. The results demonstrate that the ITDHSD system can help reduce energy consumption, greenhouse gas emissions, and improve the quality of dried products, making it an attractive option for domestic users as well as small-scale agricultural producers. The findings of this study can provide useful insights for designing and implementing sustainable and cost-effective drying systems for other food products.

Assessment of energy, exergy, environmental, and economic study of an evacuated tube solar dryer for drying Krishna Tulsi.

In the present work, experimental studies of drying Krishna tulsi leaves in an in-house fabricated evacuated tube solar collector (ETSC) connected with an indirect solar dryer are carried out. The acquired findings are compared to those obtainedfrom drying the leaves in open sun drying (OSD). The developed dryer takes 8h to dry Krishna tulsi leaves; it takes 22h in the OSD to reacha final moisture content of 12% (db) from an initial moisture content of 47.26% (db). The collector and dryer efficiencies range from 42 to 75%, 0-18%, respectively, with an average solar radiation of 720 ± 20W/m2. The ETSC and drying chamber exergy inflow and outflow vary from 200 to 1400W, 0 to60W, and from0 to50W, 0 to14W, respectively. The ETSC and cabinet exergetic efficienciesrange from 0.6-4% and 2-85%, respectively. The exergetic loss of the overall drying process is estimated to be 0-40%. The drying system sustainability indices, including improvement potential (IP), sustainability index (SI), and waste exergy ratio (WER), are calculated and presented. The value of the embodied energy of the fabricated dryer is 349.874kWh. For an expected life span of 20years, the dryer will reduce CO2 by 13.2 tonnes and earn carbon credits worth between 10,894 and 43,576 INR. The proposed dryer has a payback period of 0.4years.

Thermal performance study of a PV-driven innovative solar dryer with and without sensible heat storage for drying of Garcinia Pedunculata.

Uneven drying is the key drawback of a conventional multi-tray dryer. Therefore, an improved active solar dryer with and without integrated sensible heat storage (SHS) was proposed. A unique feature of this dryer is its movable walls from the sides of the dryer to transform it to an indirect or mixed-mode as and when necessary. Garcinia Pedunculata (GP) is a local seasonal medicinal fruit in Northeast India. Drying kinetics of GP, the dryer performance and economic analysis of dryer were evaluated in the indirect solar dryer without SHS (Exp. I), mixed-mode solar dryer without SHS (Exp. II), indirect solar dryer with SHS (Exp. III), mixed-mode solar dryer with SHS (Exp. IV), and open sun drying (OSD). The dryer's average efficiencies were 18.12%, 22.37%, 21.74%, and 24.46% for Exp. I, Exp. II, Exp. III, and Exp. IV, respectively. The moisture content of GP was reduced to 12.09% in wet basis (w.b.) from 87.99% (w.b.). The overall drying time for Exp. I, Exp. II, OSD, Exp. III and Exp. IV were 31, 26, 53, 28, and 10h, respectively. From the eleven drying models, the Two-Term model was the best-fitted model for Exp. I, Exp. II, OSD and Exp. III, and Midilli and Kucuk model was for Exp. IV. The final product's fragrance and colour are better for Exp. IV. Developing this dryer for Exp. I, Exp. II, Exp. III and Exp. IV, the price required was around 25,000, 27,000, 26,000, and 28,000 INR (1 US$ = 74.57 INR), respectively, while the economic payback periods are 1.6years, 0.9year, 1.4years, and 0.59year, respectively.

Investigation of osmosonication pretreated chili (Capsicum frutescensL.) drying in solar‐assisted fluidized bed dryer utilizing dehumidified air

AbstractThe heat and moisture sensitivity of spices and a consistent supply of electrical energy is the challenging factors in developing a relevant drying system for rural applications. A novel solar‐assisted fluidized bed dryer was developed for drying locally harvested unique spices like bird's eye chili (Capsicum frutescens L.). The chili was pretreated by the osmosonication method prior to drying to expedite the elimination of intercellular and intracellular moisture. In order to make the dryer more reliable, the recirculation strategy and dehumidified air supplied by liquid desiccant were acclimatized to constrict the heat loss through outflowing moist drying air. The experiments were conducted up to the permissible water activity (0.4–0.6) under variable drying conditions (50–70°C). By raising the ambient inlet temperature (maximum 25.9°C), the developed solar FBD was able to supply the drying air up to 50°C (in continuous mode) and a maximum of up to 65°C without aiding any heat energy sources except solar. It was found that osmosonication opened up the possibility of reducing the required drying temperature (↓10°C) and energy consumption (up to ↓31.7%). The dried red chili was fortified by pretreatment, as it could retain more capsaicin (>6%) and reddishness (>5%) compared to untreated samples. The Fourier transform infrared (FTIR) analysis showed the structural integrity of pretreated samples. The relative humidity of the drying air could be reduced by as much as 5% using the composite lithium chloride and calcium chloride (35% + 5%) desiccant dehumidifier. Dehumidification of air was found advantageous, with an inclination to shorten the drying duration (about ↓0.5 h) and energy (↓12.43%).Practical ApplicationsThere are various commercially valuable unique agro‐products that are exclusively being produced in rural areas. The inaccessibility of relevant drying technology and inconsistency of grid electricity are the main constraints in the value addition of those products. Open sun drying is most popular in rural areas; however, it is not reliable, and the product quality can't maintain. The developed solar‐assisted fluidized bed dryer utilizing dehumidifying air and integrated with osmosonication pretreatment could be a relevant technology for drying heat and moisture‐sensitive products like spices. Cost‐effective drying using locally accessible solar energy compared to open sun drying and superior dried product quality can be achieved by using the current drying system.

Design, Development and Evaluation of Photovoltaic Integrated Solar Greenhouse Dryer for Paddy

The present study was conducted at College of Agricultural Engineering, Bapatla, Andhra Pradesh, India during the month of January, 2021 to develop photovoltaic power assisted forced circulation solar greenhouse dryer and to evaluate its performance for drying of paddy. A free standing greenhouse structure with arch roof was selected to have high light transmission and low cost of construction. To get adequate and uniform light inside the greenhouse east-west orientation was selected. A frame of solar greenhouse dryer having 4.467 m length, 2.134 m width and 2.591 m height was constructed and was covered with twin wall polycarbonate sheet of 6 mm thickness. Freshly harvested paddy was filled in perforated tray with size 142.5×80×12.5 cm up to 10 cm height the trays were placed in drying chamber consists of three tires and two columns. Forced ventilation was provided with four 40 W DC fans which were powered with two 150 W photovoltaic panels. During drying, the green house and ambient air temperature, relative humidity data was collected at every 1 h interval using data logger, the moisture content of the paddy was determined at every 2 h interval. The paddy was dried till getting 12% (w.b.) final moisture content. The highest greenhouse dryer temperature of 48.1°C was recorded as compared with highest ambient temperature of34.2°C. Moreover, the air flow rate achieved was varied between 75.52‒34.25 m3m-1.In this dryer the paddy was dried from 25.3‒12.0% (w.b.) moisture content in 21 h whereas open sun drying took 28 h of drying time.

Effect of Drying Temperature on Proximate Composition and Viability of Maize Dried in a Solar Biomass Hybrid Dryer

Maize is an important cereal produced for food and feed and its nutritional composition and viability could be affected when subjected to inappropriate drying conditions. This study investigated the effects of drying temperature on the proximate composition and viability of maize grains dried at different levels in a solar biomass hybrid dryer. Proximate analysis was performed using standard A.O.A.C. methods. Germination test was done using sterilized Petri–dishes lined with filter papers to determine the viability of dried grains. Overall mean temperature, 43.63 ± 8.6 ˚C in the dryer was 9 ˚C higher than the average ambient temperature. The moisture content (MC) of grains in the dryer reduced from average 17 % to 11 % (w.b.) in 8 h at an average drying rate of 0.64 %/h. The overall drying efficiency was 12.7 % compared to 5.7 % for the open-sun drying process. The viability of grains dried in the dryer (avg. 95%) compared favourably to the viability of sun-dried grains (96%). The results show that, the temperature in the dryer had no adverse effect on the proximate nutritional composition and viability of dried maize grains. The adoption of solar biomass hybrid dryers for use by smallholder farmers is encouraged due to its suitability in providing a viable drying option to open-sun drying.