Forced Convection Solar Dryer Research Articles

Exergy and Energy Analysis of Forced Convective Thin-layer Solar Drying of Tiger Nuts (Cyperus esculantus L.)

Aims: To study the exergy and energy analysis for thin-layer solar drying of tiger nuts; and also to determine the drying kinetics for the thin-layer solar drying of tiger nuts. Study Design: Yellow variety of tiger nuts were dried in a forced convection solar dryer to determine the exergy and energy indices. Place and Duration of Study: Federal University of Technology, Owerri, Nigeria between October, 2022 to March, 2023. Methodology: The experiment was conducted at three different air velocities of 1.5, 2.5, and 3.5 m s-1 and two different loads of 70 and 140 g. The tiger nuts were dried from average initial moisture content of 52% (wb) to final moisture content of 10.2% (wb), at an average temperature range of 50.5 to 51.2 ºC. Energy utilization, exergy loss rate, exergy efficiency, improvement potential, and sustainability index were determined. Results: The results of energy utilization, exergy loss rate and improvement potential ranged from 2.1 to 5.09 W, 0.25 to 0.93 W and 0.08 to 0.54 W respectively; however, these values increased with increasing air velocities and loads. The results of exergy efficiency and sustainability index ranged from 41.8 to 68.49% and 1.72 to 3.17 respectively; these values increased with decreasing air velocities and loads. Graphical plots of moisture content with drying time showed that the moisture content of the tiger nuts decreased with increasing drying time. The characteristic nature of the curve is indicative of the fact that there was an initial higher rate of drying, which gradually declined with drying time. The results also showed that the drying rates of the tiger nuts ranged from 6.03 to 8.44 %MC/hr; and these values varied with the different air velocities and loads. Conclusion: The results from this research will serve as a guide in reduction of energy costs for the optimum design of convective dryers.

Experimental study of solar drying kinetics and evaluation of activation energy of Eriobotrya japonica fruits

AbstractGiven the seasonal nature and high perishability of Eriobotrya japonica fruits, employing effective preservation techniques like drying is crucial to minimize economic losses and extend the fruit's availability throughout the year. This study rigorously examines the drying kinetics of Eriobotrya japonica fruits using an indirect forced convection solar dryer and highlights the technological advantages of utilizing this dryer over traditional open‐air methods, showing that controlled conditions provide improved drying rates. The research develops the equation for the characteristic drying curve. The Midilli‐Kucuk model was demonstrated to be the most appropriate for describing these kinetics under various conditions, offering a reliable method for predicting drying behavior at untested temperatures. The thermal diffusivity was determined and rises as the temperature increases. The application of the Arrhenius approach enabled the determination of an activation energy of 17.79 kJ/mol, confirming the substantial impact of temperature on the drying process.Practical applicationsThe global challenge of food preservation, especially for perishable fruits like Eriobotrya japonica, requires innovative and efficient solutions to minimize economic losses and ensure the year‐round availability of nutritious produce. Our research demonstrates the technological advantages of using a forced convection solar dryer over traditional methods for drying E. japonica. This system maintains a consistent air temperature, ensuring a stable energy supply, faster, and more uniform drying. A major contribution of this study is the development of the characteristic drying curve equation, which is crucial for optimizing drying parameters and designing an efficient solar dryer specifically for E. japonica. This research not only advances the understanding of the drying kinetics and thermal properties of E. japonica but also provides a foundation for the development of more efficient and sustainable drying technologies. By optimizing the drying process, this study contributes to improving the preservation and quality of loquat fruits, thereby supporting agricultural sustainability and reducing post‐harvest losses. This work is highly relevant to the broader energy community, as it showcases the potential of solar drying technologies in enhancing food preservation while promoting the use of renewable energy sources.

Exploring Energy Performance of Taraxacum Leaves Undergoing Hybrid Forced Convection Solar Dryer

Exploring Energy Performance of Taraxacum Leaves Undergoing Hybrid Forced Convection Solar Dryer

Realization and Experimental Study of a Forced Convection Solar Dryer

Post-harvest losses represent a significant cause of food insecurity worldwide. These losses not only affect the availability of food, but they also impact the economic stability of farmers and communities dependent on these crops. Food drying presents itself as a viable solution to reduce these post-harvest losses and ensure greater availability of food for human consumption. It is in this context that our work on the creation of an indirect solar dryer with forced convection, integrating an automatic temperature control system, takes place. This study consisted of creating a prototype and subsequently carrying out drying experiments on onions in order to evaluate the performance of the device. Our experiments took place from October 25 to October 29, 2023 at Joseph KI-ZERBO University. After 8 hours of drying, only 12% of the initial mass of the onions remained. The solar thermal collector presented an efficiency of 62%. And a drying efficiency, estimated at 17% with an average sunshine of 600W/m2.

Controlling temperature using proportional integral and derivative control algorithm for hybrid forced convection solar dryer

Drying is one of the crucial processes in agricultural production, especially in grain processing. The drying process can improve grain quality and affect the grain content. However, maintaining the temperature is a challenge in the drying process. Because it can influence the drying performance and produce a low-efficiency reduction of water content, in this study, the hybrid drying system is proposed to improve the performance of the forced convection dryer system. The proposed system used a proportional integral and derivative (PID) control system to obtain the optimal temperature. The proposed system was compared with natural drying and forced convection methods. The experimental result showed that the proposed system performed excellently for three performance evaluations. The average temperature was obtained as the highest of the other methods, with 54.68 °C and 54.55 °C for coffee and cocoa beans. The water content can be reduced by an average of 27.38% and 42.67% for coffee and cocoa beans. Then, the proposed system also had the highest reduction efficiency of water content than the other methods, with 62.71% and 36.94% reductions for coffee and cocoa beans, respectively. The results indicate that the proposed hybrid system performs better than the other methods.

Energy and Exergy Analysis of Forced Convection Solar Drying of Allium Sativum With and With Out Sensible Heat Storage

In this article the energy & exergy analysis of forced convection solar dryer for drying of garlic has been investigated. The exergy parameter, air velocity has been taken to conduct the experiments and its effect on thermal efficiency. Forced draft fans were used in all the two working conditions. During the two conditions, with and without sensible heat storage system, the average air-velocities were 4.5, 9.5 and 11.4 m/s selected as ideal and subsequently its entire effect on thermal efficiency and outlet. The ambient temperatures were between (17-25) °C during the month of October and November. A DC fan is directly connected to the photovoltaic cell in the solar dryer. The thermal energy storage bed was packed with gravels with 1.5 in of thickness up to the surface of flat plate collector, the storage system becomes space-efficient. The average thermal efficiency with sensible heat storage materials was high as compared to system without sensible heat storage. The highest thermal efficiency of 61% was achieved. The maximum collector temperature obtained was 55 °C, with a mean temperature of 42 °C in the drying chamber. The collector’s greatest exergy loss was 30.38 kJ/kg and highest exergy efficiency was 70%.

Use of a forced convection solar dryer for the reduction of post-harvest losses: case of the ‘akikon’ tomato variety in benin (West Africa)

The local variety tomato (Lycopercicum esculentum Mill) named ‘akikon’ is one of the most consumed and widely cultivated fruiting vegetables in Benin Republic. In this work, we designed and built a dryer usable for limiting the frequent losses of the massive produced tomatoes. This paper analyzes the first results, obtained from the different experiments carried out with the developed dryer, in a context of forced convection. The results showed that increasing the temperature from 55 to 70 °C resulted in a shorter drying time decreasing from 1266 to 672 min with a brighter colour of the dried tomatoes for 70 °C. However, the increase of temperature does not affect the smell of the dried tomatoes. After drying, 7 to 8 months were required before we notice a colour change (from red to red-brown) of the dried product , indicating that the storage method still needs to be improved.

Single layer drying behaviour of grenade peel in a forced convective solar dryer

Solar drying experiments in thin layer of grenade peel were conducted in forced convection solar dryer consisting of a solar air collector, an auxiliary heater and a drying cabinet. Moreover, grenade peel is sufficiently dried in the ranges of 32 °C to 36 °C of ambient air temperature, 45 to 70 °C of drying air temperature, 32 to 53 % of relative humidity, 0.028 to 0.056 m3s-1 of drying air flow rate and 200 to 950 W/m2 of daily solar radiation. The experimental drying curves show only the falling drying rate period. The main factor in controlling the drying rate was the drying air temperature. The drying rate equation is determined empirically from the characteristic drying curve. Twelve mathematical models were tested to fit the experimental data. The Midilli-Kucuk model was found to satisfactorily describe the solar drying curves.

Performance investigation of an innovative solar heating unit for a powered self-sustained solar dryer

Drying food is an efficient way to prevent crop decay. However, drying techniques are known to be intensive processes in which the energy required is usually met by fossil fuels, the main sources of greenhouse gas emissions. Thus, the development of a solar-powered sustainable drying system is not only crucial for zero CO2 emissions, but also for improved energy efficiency. This study performs a comparative analysis of four solar collectors used as heating units in an indirect forced convection solar dryer. The collectors evaluated were a flat solar collector, two solar air collectors with latent thermal storage (CaCl26H2O and paraffin), and a novel heating unit combining the latter two collectors. This study conducted a comprehensive 4E analysis, evaluating the performance of the collectors through energetic, exergetic, economic, and environmental assessments. The results showed that the pioneering heating unit caused a 30 °C increase in nocturnal temperature compared to other collectors. It demonstrated an annual energy consumption of 640 kWh/year and an energy payback period of 2.5 years. The environmental analysis revealed a significant CO2 reduction of 39 tons. Overall, the proposed heating unit allows a more sustainable and cost-effective drying process while reducing greenhouse gas emissions and promoting energy conservation.

Design And Implementation of Low-Cost Solar Dryer For Sun-Dried Guava Production

Crystal guava (Psidium guajava) is a commodity that is widely cultivated in Kebumen. Innovation is needed to increase its selling value, one of which is by producing dried guava. The production of dried guava can be achieved using a solar dryer. In this research, the design and testing of a low-cost solar dryer for producing dried guava were conducted. The main materials used were wood, aluminum pipes, aluminum foil as solar collectors, and solar panels to supply power to DC fans, thus enhancing drying efficiency. The energy analysis revealed that the average collector efficiency, drying efficiency, and specific energy consumption were 73%, 8.84%, and 0.182 kWh/kg, respectively, for the forced convection solar dryer (FCSD), and 42%, 4.61%, and 0.236 kWh/kg, respectively, for the natural convection solar dryer (NCSD). Moreover, in this research, the moisture content of guava, initially at 85%, decreased to 10.73% for FCSD and 25.05% for NCSD. The payback period for this project is estimated to be 1.79 years, enabling guava farmers to use this solar dryer to enhance the selling value of their products.

Numerical Simulation of the 3D Simultaneous Heat and Mass Transfer in a Forced Convection Solar Drying System Integrated With Thermal Storage Material

Abstract The demand for quality dried products necessitates cost effective and innovative drying techniques that will improve its market value. The slow drying rate, weather dependency, and moisture reabsorption have been identified as the major challenges of solar drying operation. To address these shortcomings, hybrid solar drying systems have been recommended for the drying of various agricultural materials and other porous products. Designing a better drying system to accommodate thermal storage materials requires detailed analysis, which could be achieved through numerical simulation. Therefore, the numerical simulation of heat and mass transfer in a forced convection solar drying system integrated with black-coated firebrick sensible thermal storage materials (STSM) for the cocoa beans, locust beans, cereal grains, etc., was investigated under no-load conditions. The equations governing the fluid flow for a three-dimensional solar drying system were solved using the finite volume method with the aid of ansys, the computational fluid dynamics software to comprehend the dynamic and thermal behavior of the airflow within the dryer. The experimental maximum temperature values of 96.9 °C and 77.3 °C for the collector and drying chamber were in agreement with the simulated maximum collector and drying chamber temperatures of 116.9 °C and 80 °C respectively. The designed solar drying system with the incorporated STSM showed the capacity of raising the temperature of the air within the drying chamber to 3–37 °C above ambient temperature between 01:00 p.m. and 10:00 p.m. The agreement of the simulated dryer model with the experimental one is an indication that the developed dryer is suitable for drying cocoa, locust beans, fish, cereal grains, and some other agricultural products within an acceptable period based on the previous studies and therefore, the drying system is recommended to avoid the shortcomings associated with traditional/open sun drying.

Experimental performance analysis of a mixed forced convection solar dryer: Application to cocoa bean drying

The influence of a mixed forced convection solar dryer with thermal storage, on the quality of cocoa beans is studied. This study has as reference the quality level recommended by the international standard ISO 2451. A collection of experimental data with the realized dryer was made for six days on a sample of 10 kg of cocoa coming from the cocoa zone of Kekem in Cameroon. This sample consisted of more than 300 cocoa beans as recommended by the standard for testing. The dryer, is mainly made of wood for the frame and polystyrene for the isolating part, it has an operation based on a combination of the direct and indirect model. A control and measuring device for airflow, temperature and humidity has been installed in the drying chamber. The dryer's direct solar component can be used to accelerate the drying process, especially during the first drying phase. This experimental system was able to dehydrate cocoa beans in 2 days with a water content that went from 53.4 % to 4.6 %. From the beginning to the end of the drying process, the temperature and the relative humidity were respectively between 18 and 55 °C and between 28 and 80 %. Placing the same amount of beans in the acceleration chamber, the drying chamber and in the open air, for an amount of water to be removed of about 5.07 kg, the water removal rates were respectively about 0.32 kg/h, 0.21 kg/h and 0.10 kg/h for an effective daily average of 8 h. The drying performances of the acceleration chamber and the drying chamber are respectively 68 % and 52 %, more than the open-air drying.

Experimental investigation of an indirect solar dryer with PCM-integrated solar collector as a thermal energy storage medium.

An indirect-type forced convection solar dryer implementing a phase-changing material (PCM) as the energy-storing medium was designed, fabricated, and investigated in this study. The effects of changing the mass flow rate on the valuable energy and thermal efficiencies were studied. The experimental results showed that the instantaneous and daily efficiencies of the indirect solar dryer (ISD) increased with the initial increase in mass flow rate, beyond which the change is not prominent both with and without using the PCM. The system consisted of a solar energy accumulator (solar air collector with a PCM cavity), a drying compartment, and a blower. The charging and discharging characteristics of the thermal energy storage unit were evaluated experimentally. It was found that after using PCM, drying air temperature was higher than ambient air temperature by 9-12 ℃ after sunset for 4h. Using PCM accelerated the process by which Cymbopogon citratus was effectively dried between 42 and 59°C of drying air. Energy and exergy analysis of the drying process was performed. The daily energy efficiency of the solar energy accumulator reached 35.8%, while the daily exergy efficiency reached 13.84%. The exergy efficiency of the drying chamber was in the range of 47-97%. A free energy source, a large reduction in drying time, a higher drying capacity, a decrease in mass losses, and improved product quality all contributed to the proposed solar dryer's high potential.

Performance studies on indirect forced convection solar dryer without and with thermal energy storage during drying muskmelon slices

Performance studies on indirect forced convection solar dryer without and with thermal energy storage during drying muskmelon slices

Performance Evaluation of an Indirect-Mode Forced Convection Solar Dryer Equipped with a PV/T Air Collector for Drying Tomato Slices

This paper proposes an indirect-mode forced convection solar dryer equipped with a PV/T air collector. The PV/T air collector generates both heated air and electrical energy, which are used to force convection in the solar dryer. Experiments were carried out on selected tomato slices for which the temperature and humidity readings as well as the masses of the dried samples were instantaneously recorded for two days. A thermal analysis was performed on the solar drying system to investigate its performance. The PV/T dryer’s air temperature and velocity simulation using CFD modeling were validated by the experimental results for which the drying chamber was empty, without tomato slices. The experimental and numerical results were in good agreement. The difference between the CFD model and the experimental results for air temperature was around 1 °C (3%) and 2 °C (5%) for the solar collector and drying chamber, respectively. The average daily efficiencies of the collector, dryer, and PV panel for the solar drying system were estimated to be 30.9%, 15.2%, and 8.7%, respectively.

Experimentation of a Forced Convection Solar Dryer for Drying Sweet Potatoes at the Higher Institute of Technology of Mamou-Guinea

Experimentation of a Forced Convection Solar Dryer for Drying Sweet Potatoes at the Higher Institute of Technology of Mamou-Guinea

Convective and evaporative heat transfer coefficients during drying of ivy gourd under natural and forced convection solar dryer.

In the present work, a study on convective heat, mass transfer coefficients and evaporative heat transfer coefficient of the thin layer drying process of ivy gourd is performed. The experiment was conducted in three drying modes such as natural, forced convection solar dryer and open sun drying. The hourly data for the rate of moisture removal, sample temperature, relative humidity inside and outside the solar and ambient air temperature for complete drying have been recorded. The drying air temperature varied from 55, 65, 70 and 75°C, and the air velocity was 1, 1.5 and 2m/s. All the drying experiments had shown a falling rate period. The data obtained from experimentation have been used to evaluate the experimental constant values of C and n by simple regression analysis. Based on the values of "C" and "n", convective and evaporative heat transfer coefficients for ivy gourd were determined. The average convective heat and mass transfer coefficients varied between 2.64 and 8.30W/m2 °C and 0.0025 to 0.0076m/s for temperature ranges, at the different air velocities, respectively. The average evaporative heat transfer coefficient for ivy gourd varied from 181.89 to 421.84W/m2 °C. It was observed that convective and evaporative heat transfer coefficients increase with the increase in drying air temperature. The rate of increment of evaporative heat transfer coefficient is higher than the convective heat transfer coefficient. The intensity of heat and mass transfer during solar drying depends on the drying air temperature and velocity.

Heat transfer enhancement of solar collector by placing wire mesh stainless porous material on the solar absorber plate of indirect forced convection solar dryer

Indirect forced convection solar dryers are a common technology in solar drying. The flat plate solar collector is an essential device that absorbs heat from solar radiation in order to heat the air flowing through. To improve the thermal utilization of this device, heat transfer enhancement by using the technique of changing airflow patterns into swirling or rotating flow was proposed in this research. In the experiment, wire mesh stainless porous material (WP) SUS304 with various porosities (X) of 0.747, 0.888 and 0.928, transverse pitch with duct height ratio (P/h) of 1.14, 1.43, and 1.71, rib height with duct height ratio (R/h) of 1, attack angle (α) of 30° was placed on the solar absorber plate and the investigation conducted under solar simulator of EN 12975–2 standard with a constant solar intensity of 780±20 W/m2. Air was used as the working fluid in the turbulent flow region at Reynolds number (Re) in the range of 3,700–30,000. The experiment results showed that Nusselt number (Nu), Friction factor (f) and Thermal enhancement factor (TEF) significantly increased when WP was placed on the absorber plate because the swirling airflow through WP occurred and disturbed the thermal boundary layer on absorber plate. The increase in Re resulted in increased Nu and decreased f. Nu and f increased with a decrease in X and P/h. The highest Nu and f of 303.01 and 5.14, respectively, were found at X = 0.747 and P/h = 1.14. The maximum TEF was 1.84. Besides, the developed correlations were in good agreement with the experimental results of predicting both Nu and f with the mean differences of 6.23% and 9.98%, respectively.

Performance evaluation of PV powered solar tunnel dryer integrated with a mobile alert system for shrimp drying

The study was aimed at evaluating the drying characteristics, modelling of drying behaviour, and performance of PV powered walk-in-type semi-cylindrical forced convection solar tunnel dryer integrated with a mobile alert system using shrimps (Metapenaeus dobsoni). The dryer was fabricated using UV stabilized polythene film, CPVC pipes, and GI frames and coupled with a PV panel. A mobile alert system consisting of an Arduino UNO, load sensor, and GSM module was evaluated as an automatic data acquisition and information support system for the dryer users. Fresh shrimp samples were dried to the moisture content of 10.54% (w.b) from 79.22% (w.b) in 6 h. The graph of drying rate against the time exhibited that shrimp drying took place under the falling-rate drying period. Mathematical modelling of the drying process revealed that the Page model could accurately predict the drying behaviour of shrimp. The maximum drying efficiency of 20.22% was attained for drying shrimp in the solar tunnel dryer under forced convection. PV panel obtained an average electrical efficiency of 11.64% and supported the load requirement of 0.636 kWh/day for drying. The mobile alert system was effectively tested as an automatic data acquisition and information support system for dryer users.

Thermokinetic Study by Solar Convective Drying of Argan Press-Cake

The argan tree "Argania spinosa" is a typically multi-use tree. It represents the agroforestry systems pivot which has so far succeeded in meeting the needs of the inhabitants of arid and semi-arid areas strongly marked by climatic hazards. Argan press-cake, residue from the argan oil extraction, is used in several fields, namely: cosmetics, agriculture, and pharmacology. In order to keep this argan paste with a pennyworth, solar drying is an economically appropriate solution, energy and environmentally friendly. In this work, an experimental study is performed to improve the sun-drying process of Argan press-cake using an indirect forced convection solar dryer. As a result, the evolution of the temperature and the drying kinetics inside the product have been assessed. The influence of air recycling drying on the drying time has been highlighted and the characteristic drying law was established too. Thus, the optimal storing conditions of argan press-cake were identified.