Drying Of Agricultural Products Research Articles

Optimization of thermal photovoltaic hybrid solar dryer for drying peanuts

The drying of agricultural products is traditionally carried out using solar radiation. However, this process is time-consuming and also unreliable in locations having cold and humid environments. This study experimentally investigates an innovative air collection system integrated with a dryer. The study focuses on the drying analysis of peanuts utilizing three operational modes of a solar dryer: forced convection, natural convection, and traditional open-sun drying. Key parameters including solar radiation intensity, moisture extraction, and outgoing air temperature from the collector were studied. Solar radiation served as the primary energy source, driving the solar dryer's operation within a drying air temperature range of 33 °C–58 °C, applied to 8 kg of peanuts. Initially, the peanuts exhibited a moisture content of 72 %. The developed solar dryer subsequently reduced the moisture content of the peanut by 18 %. The study evaluated three key aspects: electrical efficiency, thermal efficiency, and overall thermal efficiency of the proposed hybrid collector and solar dryer system, conducted from 9 a.m. to 4 p.m. Results indicate that the forced convection mode of solar drying outperformed the other modes, demonstrating superior effectiveness. These findings hold significant implications for the advancement of solar dryer technology, offering valuable insights for the wider solar drying community.

Effect of channel depth ratio and absorber plate configuration on performance of a solar air heater

An experimental evaluation of the effect of channel depth ratio and absorber plate configuration on the performance of a baffled counter flow double-pass solar air heater (BCDSAH) is main objective of current work. The BCDSAH was constructed so as to permit adjustments of channel depth ratio (CDR) to 2, 3 and 4. During experimentation, the lower channel depth was kept at 50 mm while the upper channel depth was adjusted to 100 mm, 150 mm and 200 mm, yielding various channel depth ratios. The assessments were conducted for three configurations of absorber plate: (i) flat absorber plate, (ii) baffled absorber plate and (iii) baffled absorber plate with phase change material (PCM). The performance of the BCDSAH was evaluated at an air mass flow rate of 0.07 kg/s for temperature rise, useful heat gain (UHG), energy efficiency, and exergy efficiency. For CDR = 2 and a baffled absorber plate with PCM, the obtained average values of temperature rise, UHG, energy efficiency and exergy efficiency were 15.3 °C, 1075.2 W, 76.2 % and 2.7 % respectively. For the baffled absorber plate with PCM, increases of 8.5 %, 9.4 %, 10.1 % and 10.9 % were obtained in temperature rise, UHG, energy efficiency and exergy efficiency respectively for CDR = 2 compared to CDR = 4. Finally, a value of CDR = 2 and a baffled absorber plate with PCM are suitable for applications like drying of agricultural products and space heating.

Efficient simulation of bitter gourd drying in active solar dryer: A state-of-the-art model

Greenhouse drying system is used to dry agricultural products or low-temperature thermal drying using a greenhouse structure. In this paper, an experimental and simulation study is carried out to evaluate the drying performances of an active solar greenhouse dryer using COMSOL Multiphysics. The experimental setup includes a compact thermal storage-based greenhouse dryer (1.5 m × 1.0 m x 0.5 m) equipped with a black gravel-covered Aluminium jacket and 35 kg of paraffin wax for heat retention which is located on the floor of the dryer. The experiments were conducted in Ranchi, India (23.34 °N, 85.30 °E) under clear sky conditions in the month of May. The amount of solar radiation (global solar radiation) varied from (630 W/m2 to 1052 W/m2) with an average of 936 W/m2, ambient air temperature (30.2 °C–38.2 °C), air relative humidity (31.6 %–34.6 %), and wind speed (0.9–1.0 m/s). The inside dryer temperature, humidity, wind speed, and floor temperature were also measured every hour. The average values of these parameters were 59.1 °C, 30.2 %, 0.91 m/s, and 69.1 °C, respectively. The FE (finite element) modelling finds out the maximum temperature in drying products, floor and dryer's outlet is 55.3 °C,72.4 °C and 67.4 °C, respectively at 13:00 h. The proposed dryer costs 19633.50 INR with an embodied energy of 1358.01 kW h. The proposed dryer has a break-even period of 1.87 years, and its lifespan is 35 years. During this time, the net CO2 emission was found to be 21.45 tonnes, and the earned carbon credit varies from 1505.01 to 30030.00 INR. The result shows that the drying efficiency is 42.52 %, reducing the initial moisture content from 88.64 % to 2.28 % within five consecutive hours. The energy and exergy efficiencies of the dryer are found to be 61.84 % and 56 % respectively. The system is a viable, sustainable choice for the large-scale production of bitter gourd flakes.

Developing effective radio frequency drying processes for tiger nuts: Dynamic analysis of moisture state, dielectric properties and quality

Radio frequency (RF) heating technology is widely applied to dry agricultural products due to the advantages of fast and volumetric heating, but it lacks systematic and in-depth studies on combination drying methods. This study aimed to investigate the drying mechanism of tiger nuts with hot-air drying (HD), radio frequency drying (RFD), radio frequency assisted hot-air drying (RFHD), and radio frequency-vacuum drying (RFVD), in terms of analyzing dynamic changes of dehydration kinetics, moisture migration, and dielectric properties during the drying processes, as well as quality attributes of dried tiger nuts. The results indicated that the RF drying time (including RFD, RFHD and RFVD) was significantly reduced by 38.60–54.39%, compared with HD. Although RF drying had a positive effect on physical qualities, it caused clear changes to the microstructure. Among all drying methods, the free water content (A23) in the tiger nuts decreased as drying processed, while the immobilized water content (A22) increased first and then decreased. The A23 exhibited strong positive correlations with dielectric constant (ε′) and loss factor (ε″). Correspondingly, ε′ and ε″ gradually decreased due to a reduction in the A23 value. The results may comprehensively understand the RF drying mechanism of tiger nuts to provide high-quality products and optimize the drying process.

Efficiency upgrading of solar PVT finned hybrid system in Bangladesh: Flow rate and temperature influences

This research aims to determine the impact of mass flow rate and inflow temperature on the utility and effectiveness of solar thermal systems using fins with air in various applications in Bangladesh. This study examines a three-dimensional (3D) photovoltaic thermal (PVT) system where we analyze the behavior of a hybrid system with six aluminum sheets (1 mm thick fin as a heat exchange material) inside the heat exchanger where the air takes the direction to pass in waveform through the channels (made of aluminum) using fins. The top side of the fins is bent and affixed to the bottom of the floor of the PV panel to allow heat transfer utilizing the conduction-based method. This study selects inlet fluid mass flow rate and inflow temperature between (0.015–0.535 kg/s), and (10–40 °C) respectively, while comparing the result with experimental/numerical published data based on Bangladesh's weather conditions and applies the finite element method (FEM) to solve heat transfer equations. A brief analysis of the association among Reynolds number with pressure drop and fanning friction factor is included in this paper. Our model can be mounted on building rooftops or open fields where air velocity will be controlled mechanically; thus, it has many applications. This model can be implemented within an agricultural photovoltaic (APV) system, domestic functions, dry agricultural products, and provide heat for greenhouses. The result indicates that 302–514 W thermal energy has been produced for 0.015–0.535 kg/s. For growing inflow temperature, despite the reduction in electrical efficiency, the value of adding electrical and thermal efficiency (overall efficiency) comes with elevation. A 5 °C increase in inflow temperature leads to an overall efficiency increase of 0.33%. This study's findings can help researchers better comprehend air's properties as a heat exchanger in a developed design, and they can be applied to government and commercial projects.

Design and Simulation of a Multi-Channel Biomass Hot Air Furnace with an Intelligent Temperature Control System

Timely and effective drying of agricultural products is crucial for ensuring the quality and yield of grains. Biomass drying enhances energy utilization and reduces energy pressure. To this end, a novel multi-channel circulating biomass hot air furnace was designed to provide precise control of the heat source for grain drying, thereby improving the efficiency and quality of the drying process. The combustion process utilizes a multi-channel combined air supply to ensure complete combustion of biomass pellet fuel. During the heat exchange process, heat exchange plates isolate hot and cold areas, discharging combustion exhaust, while ensuring a pure air output. Using rapeseed as the drying subject, a temperature controller based on adaptive fuzzy PID was designed, targeting the biomass hot air furnace’s heat exchange system for modeling and verifying the model with the step response method. Model simulations were conducted in Matlab’s Simulink module using both adaptive fuzzy PID and traditional PID controllers, for a given signal. The settling times for the conventional PID and fuzzy PID were 445 s and 364 s, respectively, with overshoots of 20.1% and 6.3%, showing that the fuzzy PID controller performed better in terms of control performance. The validation tests showed that both control methods could maintain the temperature within ±5 °C. Compared to traditional PID control, the adaptive fuzzy PID control achieved a precision of ±3 °C. At the target temperature of 90 °C, the error was reduced to 3.7%, with a stabilization time of 1014 s. The use of fuzzy PID control exhibited better dynamic response characteristics, meeting the drying needs of rapeseed. This study provides a theoretical basis for the structural design and control system design of biomass hot air furnaces.

Spouting Technology in Energy-Carrying Electromagnetic Field Drying of Agricultural Products

Spouting Technology in Energy-Carrying Electromagnetic Field Drying of Agricultural Products

Development and Performance Evaluation of a Novel Solar Dryer Integrated with Thermal Energy Storage System for Drying of Agricultural Products.

Passive solar dryers play a crucial role in reducing postharvest losses in fruits and vegetables, especially in regions like sub-Saharan Africa with low electrification rates and limited financial resources. However, the intermittent nature of solar energy presents a significant challenge for these dryers. Passive solar dryers integrated with thermal energy storage (TES) can reduce intermittence and improve the drying efficiency. Currently, phase change materials (PCMs) are popular heat storage materials in dryers, and paraffin wax dominates. The main problem with the use of PCMs is that it is necessary to closely constrain the temperature range of the process during charging and discharging. This can be a difficult condition to meet in simple solar dryers due to the variable availability of solar radiation. Instead, solid-phase materials, such as sand and rocks, are often used. Soapstone is one of the natural rocks with good thermal properties, but it has yet to be used as a TES material in solar dryers for drying agricultural products. Therefore, the main objective of the present study was to develop a novel solar dryer integrated with soapstone as a TES material and evaluate its performance. The proximate analysis to examine the quality of dried products using the developed technology was also carried out. The comparative experiments for the developed dryer were conducted in two modes: dryer with TES materials and without TES materials, and the results were compared with open sun drying (OSD) by drying 50 kg of fresh pineapple and carrot at different times. The drying times for pineapples in the dryer with TES, without TES, and OSD were 13, 24, and 52 h, respectively. However, the drying times for carrots in the dryer with TES, without TES, and OSD were 12, 23, and 50 h, respectively. Notably, the dryer integrated with TES materials could supply heat for around 3-4 h after sunset. The thermal efficiency of the dryer, collector efficiency, and storage efficiency of TES materials were calculated and found to be 45, 43, and 74.5%, respectively. Proximate analysis indicated that the dryer integrated with TES materials effectively maintained the quality of the dried products compared to OSD. Solar dryer integrated with soapstone showed great promise as sustainable and efficient solutions for reducing postharvest losses and enhancing food security in resource-constrained regions like sub-Saharan Africa.

Modeling convective and intermittent drying of agricultural products

The purpose of this work is to quantify the energetic interest of convective and intermittent drying process of natural products. This drying mode has been achieved within a climatic blower. This laboratory device permitted us to achieve several tests for different conditions of drying for apples, carrots and peppers. This study permitted to appreciate the capacity of the model to describe the different drying periods. In the continuous case, a variation of the air velocity permitted us to find the most economic velocity for the drying of thin layer products. In the intermittent case, the numerical simulation profiles give us more information on what happens really to the product during periods of stop. Besides, the drying kinetics at the retaking increases with the air temperature. Then, we gain in energy and in global drying time.

Optimum scheduling of shared greenhouse solar dryer in Thai community

Drying agricultural products is crucial in improving product quality and reducing post-harvest losses, ultimately increasing income for farmers. Greenhouse solar dryers (GSD) amplify these benefits by enhancing quality, preserving nutrients, and extending shelf life, thus elevating the economic worth of agricultural products. However, optimizing GSD utilization faces challenges from seasonal crop patterns, limited variety, and uncertain yields, curbing their full economic potential. Therefore, GSDs must be shared among farmers to address the underutilization of the infrastructure and increase the community’s overall profit. In addition, prioritizing higher value-added goods further maximizes gains from the shared infrastructure. Considering these factors, this research aims to demonstrate the financial benefits of sharing GSDs within a community. To determine the optimal sharing schedule, a mixed-integer linear programming (MILP) model is formulated that considers the monthly production of fresh and dried products, with their corresponding prices and value-added. We tested the model’s performance under three different sharing schemes using the data of a typical Thai agricultural community. It is clearly shown that by sharing the GSDs and importing products to fill empty days, the utilization rate of the GSD can be increased from 23% to 62% by following the optimal schedule. Besides, this approach can boost the overall profit of the community by 1.6 times compared to individual GSD utilization practices. The proposed concept provides a robust schedule for dependable and profitable sharing, even amid unpredictable conditions. However, realizing these benefits entails managing additional challenges, highlighting the need for intelligent unit support for successful community-sharing GSD implementation.

Manufacturing and Evaluating of Indirect Solar Dryers

–Indirect solar drying uses solar radiation to heat air and dry agricultural products in harvest time to store them for a longer time and reduce waste. The dryer consists of a solar air heater collector, a drying chamber, and an air ventilation system. In this study, an indirect solar dryer system is constructed and ventilated with an electrical fan. Experiments are conducted on the system using eggplant as an agricultural sample on 2 consequent days (29th and 30th October 2022), to evaluate the system data recorded during the drying process in terms of the temperature for points in the system, solar radiation, and the sample mass. The temperature measurements are ambient, collector, and dried chamber outlet temperatures. The results show that the most effective time for solar drying is between 9:00 and 16:00, and the drying system air temperature is raised to about 40°C when solar radiation reached more than 600 W/m2 in the noon time. The weighted mass is used to evaluate the drying process, and maximum drying rate and drying efficiency are obtained on the 1st day of the drying before noon time.

Recent Progress and Application of Freeze Dryers for Agricultural Product Drying

AbstractThe impact of various freeze‐drying (FD) methods on the drying efficiency and quality of dried fruits and vegetables is reviewed. Additionally, a brief overview of recent advances in FD methods is provided. The FD technique is characterized by the following key properties: ability to maintain original texture and color, the highest nutritional value, and appropriate rehydration rate due to the porous tissue of the product. Recently, various combination methods have been tested to improve the drying speed and save energy when FD fruits and vegetables. This includes combining FD systems with other techniques such as ultrasound, microwave, vacuum, infrared radiation, pulsed electric field (PEF), and CO2 laser perforation. Combined benefits of these technologies include increased mass transfer rates, shorter dehydration time, energy savings, improved product quality, lower shrinkage, higher rehydration capacity, and flexibility to dry and manufacture the many types of dried fruits and vegetables pieces.

Recent Progress in Solar Dryers using Phase Changing Material: A Review

The most recent developments in the use of phase change materials (PCM) in solar dryers around the globe are summarised in this review article. The article emphasises the benefits of utilising PCM in solar dryers, including enhanced thermal performance and accelerated agricultural product drying. The review discusses the various PCM kinds and their characteristics, as well as the various arrangements of solar dryers that use PCM. The difficulties and restrictions of employing PCM in solar dryers are also covered in the study, including the need for careful PCM integration and selection as well as the complexity of PCM modelling. Overall, the study offers a thorough summary of the status of research on PCM-based solar dryers and offers insights into potential future research areas.

Thermo-economic and drying kinetic analysis of Oleaster using a solar dryer integrated with phase change materials and recirculation system

Drying of agricultural products is a good way to store wet products. In recent decades, using solar dryers has received much attention due to the environmental problems of using fossil fuels. However, one of the main problems of solar drying system is the low thermal efficiency and inhomogeneous distribution of temperature in the drying chamber. In this work, the increase of heat efficiency of flat plate collector has been investigated using phase change materials and air recirculation mechanism. Copper pipes containing phase change material, at the top of the collector plate vertically at three 5, 10 and 15 cm intervals. Drying process of Oleaster fruit was used to evaluate the drying performance of the solar dryer. The results revealed that using air recirculation system and thermal storage systems improved the drying efficiency and thermal efficiency it was about 43.42% and 16.75 %, respectively. The average thermal efficiency for distances of 5, 10 and 15 cm was 53.26, 54.89 and 56.29 %, respectively. Using return air flow increased the thermal efficiency at least 11.65 %. By economical optimization about 8.6 %. The best mathematical to predict the drying was Henderson and pabis. Moreover, the results indicated that applied CFD model predicted the thermal performance of the dryer at acceptable range (with low relative error 2.56 ± 0.32%). Based on the optimization process the proper arrangement of PCM tubes inside of the collector was obtained.

Computational modelling for decarbonised drying of agricultural products: Sustainable processes, energy efficiency, and quality improvement

Drying agricultural products consumes massive amounts of energy. The rapid depletion of non-renewable energy sources, along with rising environmental concerns, are opening up new opportunities for developing sustainable drying systems and reducing its carbon footprint. Drying modelling is a powerful tool for understanding the mechanism and predicting fluid flow hydrodynamics and heat and mass transfer during the drying process. The current review outlines the state-of-the-art of various modelling techniques for drying technologies, explores the unresolved bottlenecks in technology development, and provides new avenues for more innovative and sustainable drying technologies. First, the drying mechanism and novel drying technologies are explained. Then, various modelling methods are summarised. Finally, new insights into quality and energy modelling using CFD are discussed. Based on the research achievements, future challenges of CFD modelling and their contribution to improving the drying process in terms of high quality and low energy consumption and decarbonisation are addressed. • A comprehensive understanding of the drying mechanism is indispensable in CFD modelling. • Energy and environmental concerns create new avenues for developing sustainable drying. • CFD is conducive to heat and mass transfer prediction and drying parameter optimisation. • Modelling the drying process should be geared towards integrating energy and quality aspects.

Concentrated solar powered agricultural products dryer: Energy, exergoeconomic and exergo-environmental analyses

Only energy-efficient and sustainable drying processes can ensure a long-term and safe storage of agricultural products. Therefore, in this study, a multi-conical solar concentrating system is proposed for drying of various agricultural products. This paper focuses on multiple aspects of performance including energy, exergo-economic and exergo-environmental performance analyses. Copper oxide/water nanofluid was used as a heat transfer medium and the drying characteristics of green pumpkin and carrot slices were studied as samples application. It was found that the proposed multi-conical solar dryer showed a significant improvement in the thermal performance, and the drying time which takes to reach the set drying temperature was reduced by 40% related to the conventional solar dryers. In addition, the inside temperature of the dryer was well maintained at the set temperature for 10 h. Using multi-conical solar dryer, the average values of exergy efficiency and exergy loss were found to be 38.08% and 0.61 kW, respectively. In context of economic and environmental analyses, the energy payback time and CO2 mitigation for the expected lifetime of CuO nanofluid based solar dryer were 4.38 years and 13.41 tons, respectively, and with water as a heating medium these values were found to be 7.65 years and 10.39 tons, respectively. The performed assessments revealed that the nanofluid powered multi-conical solar drying system is highly efficient for drying of agricultural products at an industrial scale.

Experimental Performance Analysis Of Free And Forced Fully Developed Air Flow Green House Solar Dryer Using Curry Leaves

The world is beginning to move away from its consumption of fossil fuels. Various technologies are being developed to make use of renewable energy sources such as wind, solar, and tidal, etc. Solar energy is the best choice among these sources because of it is readily available, abundant, and capable of producing both electric energy and space heating. Solar energy can be used directly or indirectly to dry agricultural and non-agricultural products to preserve them for long a period without formation of fungi. Drying of herbal leaves is an important process in Siddha and Ayurvedic industries to produce herbal medicines in power form. However, as herbal leaves are dried in the open sun, they are susceptible to environmental factors such as rain, insects, and livestock. These disadvantages of open-air drying shall be overwhelmed by greenhouse solar dryer. Greenhouse solar dryer with natural convection, forced convection with hot air supply are the existing methods, but when supplied with hot air, the rise in temperature leads to nutrient loss in herbal leaves. In order to avoid this loss in nutrients, the current work gives a solution that the temperature of forced convection greenhouse dryer can be reduced and controlled by supplying the ambient air at inlet flow in a fully developed air region, and this method can also leads to reduction in colour loss with possibly same or higher drying rate compare to natural convection greenhouse dryer.

Study of the temperature and humidity regime in solar drying of agricultural products

This article presents the results of experiments on the temperature and humidity regimes in the drying chamber when drying apples and apricots in a refrigerator with a combined solar collector and heat pump. The combined dryer is designed for simultaneous drying and long-term storage of the product. Experiments on the study of temperature and humidity regimes were carried out under natural convection conditions. Experimental studies of temperature and humidity regimes showed that the maximum temperature inside the chamber reached 46 oC and the maximum humidity reached 62%, and in these temperature and humidity regimes, apples were dried in 30 hours and apricots in 48 hours. From a product with a starting mass of 5 kg, 0.65-0.7 kg of dried product was obtained. Experimental results on temperature and humidity during drying of apples and apricots t=f(h) and w=f(h) and presented in the form of a dependency graph.

A Prototype Passive Solar Drying System: Exploitation of the Solar Chimney Effect for the Drying of Potato and Banana

Agricultural product drying is of great importance as it is a reliable method for fruit and vegetable preservation. Tackling the high energy consumption of the process will reduce the final product cost and mitigate greenhouse gas emissions. In this work, a passive drying method was experimentally evaluated. The method was based on the principle of the stack effect taking place in the solar chimney structure. Different types of solar chimneys in terms of dimensions and materials were evaluated for the drying of banana and potato slices. The results of the experiments showed that the drying rate was close to solar drying systems. Parameters such as height and material characteristics of drying tubes, as also weather conditions, influenced the drying rate. It was found that the banana and potato slices were dried at a satisfactory rate for almost 48 h during the summer period in Greece. From the parameters of the drying tubes that were varied, it was found that both the height and material played a major role, as did the air flow rate. With the increase in the drying tube by 1 m and with the choice of proper manufacturing material, an increase in the flow rate between 40% and 100% can be achieved. When only the color of two 3 m-high tubes changed, the flow rate varied between 4% and 15%. The proposed method has almost zero energy consumption, and it could be used as a standalone or as a part of a hybrid drying system. It can also be adjusted in existing greenhouse-type agricultural structures as a parallel operation system.

CFD Analysis of a Small-Scale Solar Chimney Exposed to Ambient Crosswind

Solar chimneys are devices that use solar energy to generate a hot airflow that can be used for power production, the drying of agricultural products, and/or water desalination. The performance of a small-scale solar chimney is studied numerically. The computational domain includes the solar chimney, the ground, and the atmosphere. The turbulent airflow is simulated using the commercial CFD code Ansys Fluent. The only boundary conditions required for the simulation are the wind speed, the ambient temperature, and the absorbed energy from the ground, determined by an energy balance in the system. The system was simulated for one day in the summer in the city of Belo Horizonte, Brazil. The ambient crosswind plays an important role in the velocity and temperature. The velocity inside the solar chimney increased with the wind speed, increasing the heat transfer and decreasing the airflow temperature. When the wind speed increased from 0 to 10 m/s, the outlet velocity increased from 1 to 4 m/s, and the outlet temperature decreased from 313 to 304 K.