scholarly journals An Experimental Study of Vegetable Solar Drying Systems with and without Auxiliary Heat

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Abdul Jabbar N. Khalifa ◽  
Amer M. Al-Dabagh ◽  
W. M. Al-Mehemdi
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Solar Drying ◽  
Drying Time ◽  
Exponential Equations ◽  
Drying System ◽  
Auxiliary Heater ◽  
Best Fit ◽  
Drying Chamber ◽  
Natural Drying

An experimental study is conducted to investigate the performance of a solely solar drying system and a system equipped with an auxiliary heater as a supplement to the solar heat. The performances of both are compared to that of natural drying. Beans and peas are dehydrated in a system that consists of two flat plate collectors, a blower, and a drying chamber. Tests with four different airflow rates, namely, 0.0383, 0.05104, 0.0638, and 0.07655 m3/s are conducted. It was found that the drying time was reduced from 56 hours for natural drying to 12–14 hours for solar drying and to 8-9 hours for mixed (solar and auxiliary) drying. The efficiency of the mixed drying system was found to increase by 25% to 40% compared to the solely solar drying. A best fit to the experimental data of peas and beans was obtained by six exponential equations for the various systems with a correlation coefficient in the range 0.933 and 0.997.

scholarly journals РАЗРАБОТКА И ИСПЫТАНИЕ СОЛНЕЧНОЙ УСТАНОВКИ С ПОЛИКАРБОНАТНЫМ ПОКРЫТИЕМ ДЛЯ СУШКИ ПРОДУКТОВ СЕЛЬСКОГО ХОЗЯЙСТВА

World Science ◽  
2021 ◽  
Author(s):  
Ketevan Archvadze ◽  
Ilia Chachava ◽  
Ketevan Papava ◽  
Nanuli Khotenashvili ◽  
Riva Liparteliani ◽  
...  
Keyword(s):  
Vitamin C ◽  
Air Temperature ◽  
Laboratory Analysis ◽  
Agricultural Products ◽  
Solar Drying ◽  
Drying Process ◽  
Drying Time ◽  
Drying System ◽  
Natural Drying

The proposed solar drying system significantly reduces the drying time and improves the quality of the product, including the preservation of vitamins. When drying rosehip, a laboratory analysis for vitamin "C" showed that 28% of this vitamin is destroyed during natural drying, and 17% when using a solar dryer.The drying speed increases by 2.5 - 4 times compared to traditional outdoor drying.In the proposed installation, you can dry different agricultural products, you can change the coating of the solar drying unit. In S/D, the air temperature is higher than in the environment from about 13 to 32 degrees Celsius, depending on weather conditions.The drying process in the S/D apparatus allows you to ensure the purity of the products. S/D is covered and during the drying process the product is not contaminated with dust and rain, by influence of dew, is not damaged by birds, insects or wasps.This device is convenient for transportation, during the day it can be moved and rotated to align to the sun.The proposed solar dryer is easy to manufacture and can be widely used in large and small farms, private and subsidiary farms.

An Indirect Passive Solar Dryer for Drying

2011 ◽  
Vol 367 ◽  
pp. 517-524
Author(s):  
A. F. Alonge ◽  
O. O. Oniya
Keyword(s):  
Moisture Content ◽  
Initial Moisture Content ◽  
Solar Drying ◽  
Drying Time ◽  
Sun Drying ◽  
Two Samples ◽  
Drying System ◽  
Average Size ◽  
Local Materials ◽  
Drying Chamber

A solar drying system designed on the principles of convective heat flow, constructed from local materials was employed in drying yam (Dioscorea Alata). A glass collector having an efficiency of about 0.63 was used along with an absorber for absorbing the heat energy. The drying chamber consisted of drying trays. A chimney fitted at the top centre of the drying chamber enhanced airflow. Air passing through the collector heated up and dried the foodstuff in the drying chamber. The latitude of Ilorin is 8.26oN and the collector angle could be varied . 56o C, 41o C and 71o C were obtained as the maximum attainable temperatures for the drying chamber, ambient and collector respectively. Two samples of yam chips, each weighing 1560g and having an average size of 1cm thick, were dried both inside the dryer and outside the dryer within its surrounding. The initial moisture content of the yam was 70.3% (wet basis) and its final moisture content was 9% (wet basis).The result was compared to natural sun drying. It was observed that the drying time was reduced from 52 hours for sun drying to 45 hours for solar drying. The total cost of the construction was 6, 105 Naira.

Performance of a Solar Drying System Driven by a Hybrid Power System

2012 ◽  
Vol 455-456 ◽  
pp. 139-146
Author(s):  
Hao Zhong ◽  
Zhi Min Li ◽  
Tong Wu ◽  
Ming Jiu Yu ◽  
Run Sheng Tang
Keyword(s):  
Power System ◽  
Early Stage ◽  
Initial Moisture Content ◽  
Agricultural Products ◽  
Solar Drying ◽  
Test Results ◽  
Drying Time ◽  
Drying System ◽  
Drying Chamber

To increase the production and improve the quality of dried agricultural products, a new drying system with a hybrid driving power system was developed and tested. The system with total collector area of 100m2 is consisted of 10 drying units and each of them is consisted of 5 identical air collectors and a greenhouse-like drying chamber. Each of collectors in the system is equipped with a DC fan, powered by either 120W solar modules or a 300W wind turbine, and an AC fan, directly powered by the electricity from grid. Such drying system can operate in all time of any day and avoid any possible spoilage of dried products as found in conventional solar dryers due to the formation of mould on the surface of dried materials in the events of consecutive rainy days. Field test for the drying of 9 fruits was conducted from November to December in 2005. The results indicated that the system was very effective for the drying of fruits and the solar drying time for most of the materials to be investigated was only one third of that required in the natural sun drying. Test results also showed that the nocturnal ventilation of drying chambers at the early stage of drying exercise was necessary for materials with high initial moisture content in order to further shorten the solar drying time.

Experimental Study of Notoginseng Drying Based on a Solar Air Heating System

2011 ◽  
Vol 71-78 ◽  
pp. 2073-2076
Author(s):  
Fen E Hu ◽  
Zhi Juan Wang
Keyword(s):  
Winter Season ◽  
Heating System ◽  
Solar Drying ◽  
Mass Rate ◽  
Drying Time ◽  
Air Heating ◽  
Solar Air Collector ◽  
Air Blower ◽  
Drying System ◽  
Air Channels

A solar air drying system including solar air collector, drying cabinet and air blower for notoginseng drying has been constructed and tested. Two identical air solar collectors with two air channels, V-groove absorption heat plates and a single glass cover have been employed. The results of test show that the solar air collectors can obtain a good thermal performance in winter season. When the air flow mass rate is fixed at 0.0597kg·s-1, the maximum values of thermal efficiency and outlet air temperature are 76.0% and 62.2°C, respectively. The experimental analysis between two sampling notoginseng drying suggests that the solar drying is very effective, and the drying time has been shorten to about 440 minutes from 990 minutes of the traditional drying by sun. It is also observed that using the solar drying system notoginseng has a higher quality than traditional drying method.

scholarly journals Mathematical modeling of pequi pulp drying and effective diffusivity determination

2017 ◽  
Vol 21 (7) ◽  
pp. 493-498 ◽  
Author(s):  
Elisabete P. de Sousa ◽  
Rossana M. F. de Figueirêdo ◽  
Josivanda P. Gomes ◽  
Alexandre J. de M. Queiroz ◽  
Deise S. de Castro ◽  
...  
Keyword(s):  
Experimental Data ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Drying Time ◽  
Air Speed ◽  
Drying Curves ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Best Fit

ABSTRACT The aim of this work was to study the drying kinetics of pequi pulp by convective drying at different conditions of temperature (50, 60, 70 and 80 °C) and thickness (0.5, 1.0 and 1.5 cm) at the air speed of 1.0 m s-1, with no addition of adjuvant. The experimental data of pequi pulp drying kinetics were used to plot drying curves and fitted to the models: Midilli, Page, Henderson & Pabis and Newton. Effective diffusivity was calculated using the Fick’s diffusion model for a flat plate. It was found that, with increasing thickness, the drying time increased and, with increasing temperature, the drying time was reduced. The Midilli model showed the best fit to the experimental data of pequi pulp drying at all temperatures and thicknesses, presenting higher coefficients of determination (R2), indicating that this model satisfactorily represents the pequi pulp drying phenomenon. There was a trend of increase in the effective diffusivity with the increase in pulp layer thickness and temperature.

Improvement of the Thermal Performance of Solar Drying Systems Using Different Techniques: A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Messaoud Sandali ◽  
Abdelghani Boubekri ◽  
Djamel Mennouche
Keyword(s):  
Heat Pump ◽  
Climatic Conditions ◽  
Operating Conditions ◽  
Solar Drying ◽  
Drying Time ◽  
Buoyant Force ◽  
Circulation Mode ◽  
Solar Dryer ◽  
Drying System ◽  
Air Circulation

Solar drying is one of the most important processes of preserving agricultural products. This review paper focused mainly on the enhancement of efficiency a solar drying system. The establishment of different techniques and factors, which may affect the performance of solar dryers, helps to improve solar dryers’ effectiveness. Different types of solar dryers were described here; moreover, various performance analyses of solar drying systems (SDSs) were presented. Factors and techniques for improving efficiency of solar dryers were discussed as well. The effect of operating conditions, geometrical conditions, adding of reflectors, heat exchanger, heat pump, photovoltaic source, air circulation mode, and phase change material (PCM) on the efficiency of a solar drying system were studied and discussed. Results showed that climatic conditions such as ambient temperature and solar radiation have an important influence on the solar dryer performance. The chimney integrated in solar dryer increases the buoyant force applied on the air stream to maintain a greater air flow velocity, which removes one side of moisture. The concentrators found to be effective in reducing the drying time by increasing the air temperature inside the dryer. Photovoltaic panels provides electricity source to run electrical components such as the fan to provide a forced air circulation that removes more moisture from the product compared with the natural convection or the heat pump to ensure the drying process at night. PCMs store the thermal energy during sunshine hours and release it after sunset, which can reduce the heat losses and improve the thermal efficiency of the drying system.

scholarly journals Performance Enhancement of a Sludge Continuous Feed Heat Pump Drying System by Air Deflectors and Auxiliary Cooling Subsystems

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6651
Author(s):  
Win-Jet Luo ◽  
Cheng-Yan Lin ◽  
Nai-Feng Wu ◽  
Zhi-Qun Xu
Keyword(s):  
Performance Enhancement ◽  
Heat Pumps ◽  
Drying Time ◽  
Operational Conditions ◽  
Subsystem Design ◽  
Airflow Field ◽  
Continuous Feed ◽  
Drying System ◽  
Improved Design ◽  
Drying Chamber

This study proposes an improved design for a typical sludge continuous feeding drying system connected with three air-source heat pumps. The system’s performance was further improved using air-deflectors on the drying chamber’s internal sidewalls, enhancing the heat and mass transfer between the conveyor sludge and circulating airflow. In this study, numerical analysis was performed to elucidate the deflector designs on the airflow field and thermal temperature field distributions in the drying chamber. The specific moisture extraction rate (SMER) value was quantified to evaluate the system’s overall improvement during experiments. With a suitable deflector design, the average percent water content in sludge could be further reduced to 22.2% with drying time of 18.3 h, and the SMER value could be enhanced from 1.38 kg/kWh to as high as 1.83 kg/kWh with an increment of 32.44%. Moreover, to prevent overloading and frequent shutdown of the compressors, an auxiliary cooling subsystem was designed to attain stable operational conditions. By the auxiliary cooling subsystem design, the compressors’ shutdown can be avoided, the temperature difference between airflow inlets and outlet of the drying chamber can be increased, and SMER value can be further increased to a value of 1.94 kg/kWh.

A Mathematical Model Of Solar Drying Of Rice

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Pyseth Meas ◽  
Anthony H.J. Paterson ◽  
Donald J. Cleland ◽  
John E. Bronlund ◽  
A. John Mawson ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Moisture Transfer ◽  
Solar Drying ◽  
Algebraic Equations ◽  
Drying Time ◽  
Nonlinear Algebraic Equations ◽  
Drying System ◽  
The Many ◽  
Heat And Moisture ◽  
Practical Accuracy

Abstract A mathematical model describing the heat and moisture transfer within a solar drying system of rice was formulated. A numerical solution using MATLAB was implemented due to the many coupled PDEs and nonlinear algebraic equations. The model was checked for a range of the space steps and by comparison to analytical solutions for completed situations and was shown to contain no significant numerical errors. After estimating the best values and uncertainties of the system inputs the model was validated by comparison with experimental data for solar drying of rice. It was shown to be a very good mechanistic tool with advantages of simplicity and practical accuracy. The model accurately predicted the drying time and the temperature, and moisture content (MC) within the bed during drying except when a polystyrene drying pad was used. However, the model did not predict the experimental bed water activity (relative humidity) consistently well.

scholarly journals Design and Analysis of a Novel Drying Chamber in Indirect Forced Convection Solar Drying

2020 ◽  
Vol 9 (9s) ◽  
pp. 11-16
Keyword(s):  
Energy Efficiency ◽  
Forced Convection ◽  
Solar Collector ◽  
Ambient Air ◽  
Drying Rate ◽  
Solar Drying ◽  
Drying Time ◽  
Hot Air ◽  
Drying Chamber ◽  
Effective Distribution

Long drying time and less control on drying parameters in natural convection drying give way to forced convection indirect solar drying. In forced convection drying, an external blower supplies ambient air into the solar collector. The incoming air gets heated inside the collector and this air then flows into the drying chamber where the product to be dried is kept. The hot air absorbs the moisture from the raw crops and exits through the chimney. Along with the temperature and humidity of incoming air, its distribution inside the drying chamber is also important in the process of drying. The drying rate and quality can be improved if these parameters are under control in forced convection solar drying. In this paper, design and analysis of a novel drying chamber are presented to improve the performance and energy efficiency of solar drying with effective distribution of air inside the chamber. The variation of velocity with respect to different positions inside the drying chamber is also studied numerically.

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