A Design for Experimental Drying Apparatus for The Determination of The Impact of The Affecting Factors on The Drying Time and Performance for Fruits (original) (raw)
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Thin-layer drying rates of fig fruits were determined experimentally under different conditions of the drying air temperature, relative humidity and velocity, and under different initial moisture content of the fruits. Twenty-four drying tests were run by an experimental dryer, locally designed and fabricated for thin-layer drying. The results showed that the drying air temperature, the fig fruits initial and final moisture content had the greatest effect on the drying rate of fig fruits, followed by the drying air relative humidity. Air velocity had the least effect. The objectives of this research work could be summarized as: expressing the loss of moisture during the drying process of the fruit or the vegetable, as a function of the affecting factors of the drying process, the determination of the fruit or the vegetable drying rate as a function of all the affecting factors, the determination of the needed time through each stage of the drying process, and how to benefit from the findings of this research work in conducting productive drying operation of fruits on large scale. This work was planned for mathematically expressing the loss in fig fruits moisture throughout the drying process as a function of the affecting factors using multiple linear regression analysis. The derived mathematical expressions which relate the results of the drying process with the affecting factors could be used in the determination of the instantaneous moisture content of the fruits at successive time intervals. These equations are especially useful for solar drying under which the drying air properties are under continuous changes along the time of the day and along the days of the year. The derived mathematical equations covered all the stages of the drying process, i.e, the stage of the primary increasing drying rate, the stage of the constant drying rate and the stage of the falling drying rate.
Thin-layer drying rates of fig fruits were determined experimentally under different conditions of the drying air temperature, relative humidity and velocity, and under different initial moisture content of the fruits. Twenty-four drying tests were run by an experimental dryer, locally designed and fabricated for thin-layer drying. The results showed that the drying air temperature, the fig fruits initial and final moisture content had the greatest effect on the drying rate of fig fruits, followed by the drying air relative humidity. Air velocity had the least effect.
Journal of food Engineering, 2004
In order to establish the influence of the drying air characteristics on the drying performance of figs (ficus carica) several drying tests have been carried out in a laboratory scale tunnel-dryer. The dryer using ambient heated air and working in closed loop was equipped with a continuous monitoring system. The investigation of the drying characteristics has been conducted in the temperature range of 55–85 °C and the airflow in the range of 0.5–3 m/s. An Arrhenius-type equation was used to interpret the influence of the drying air parameters on the effective diffusivity, calculated with the method of slopes in terms of energy of activation, and this was found to be insensitive to air velocity values higher than 2 m/s. The effect of the air temperature and velocity on the drying constants was determined by fitting the experimental data using regression analysis techniques. The influence of the air temperature on the drying kinetics of figs has been shown to follow the Arrhenius relationship. The strong influence of air temperature and velocity at the early stages of drying was evident, as well as the relative insensitivity of the drying process at the later stages. A value beyond which the increase of the airflow velocity has no significant effect on the drying rate was encountered and was determined to be 2 m/s, indicating the predominance of the internal mass transfer resistance over the external one. The investigation revealed that the drying kinetics is most significantly affected by temperature, with the airflow velocity having a limited influence on the drying process. Correlations expressing the drying constants and effective moisture diffusivity dependence on the drying-air parameters are reported.
Drying Characteristics of Fruits using Solar Drying
2016
In this study, a solar dryer system designed to use convection sources of energy for drying agricultural product it is expensive process in developing countries. This research is a try to develop a solar dryer for figs. The aim is to produce a drying fig with good quality and decrease the drying time. Five different indirect design concepts were presented. All concepts that generated are indirect forced and natural convection of solar energy. All generation consists of the same dimensions and material made. One design concept was chosen after screening process which consists of a solar collector, a drying chamber, and chimney. Finally, the result was discussing five experiments that did to obtain the higher performance of solar dryer. The result recorded the average chamber temperature is 59°C compared with average ambient temperature is 32 °C. The theoretically result presented the dryer efficiency is 17.6%.
MATHEMATICAL MODELING FOR DRYING FIGS IN THIN LAYER USING MECHANICAL DRYER
In the present work, selected mathematical thin-layer drying models were fitted to experimental data using non-linear regression analysis techniques. The drying behavior was examined and simulated using four different thin layer drying models (simple, modified simple, logarithmic and two-term exponential model). An empirical equations relating the studied drying parameters with the drying constants of each model were also developed. The analysis was conducted based on the final moisture content (Mf) and the equilibrium moisture content (Me) for calculating the moisture ratio (MR). The results indicated that, both forms of different drying models equations described the drying behavior of whole figs satisfactorily as indicated by the high values of coefficient of determination (R 2 ) and low values of standard error (SE).
DRYING FIGS USING DEVELOPMENT MECHANICAL DRYER
The present work was conducted to study and simulate the drying behavior of whole figs fruits under different drying parameters. The approach led to develop a small scale industrial figs dryer using butane-gas as heat energy source and also describe the change in whole figs moisture content during actual drying process using the proposed dryer. The experimental were carried out using fresh whole figs "Ficus Carica" its local name is "Sultani". Whole figs fruits were treated before drying by treatment (A): the fruits sulfured by dipped in 1. 5% aqueous sodium metabisulfit and, treatment (B): the fruits were dipped in 1% sodium hydroxide before treated with solution of 1.5% sodium metabisulfit. Four levels of drying air temperature (55, 65, 75 and 85 °C) and four levels drying air velocity (0.2, 0.4, 0.6 and 1 m/s) The dryer has been developed and tested for drying whole figs fruits at Agriculture Engineering Department, Faculty of Agriculture, Kaferelsheikh University. The results showed that, the reduction rate of whole figs moisture content was increased with the increasing of drying air temperature and air velocity in all pretreatment of simple whole figs. On the other hand, the whole figs moisture content reduction rates on the treatment (B) were higher than that in treatment (A) for all the combination of the parameters. The recorded drying time for drying whole figs from an initial moisture content of about 223-400% d.b to a final moisture content of about 18-20 % d.b were 35-20 hours under different drying parameters. Heating control unit using butane-gas was used to control heat source in drying air temperature with fluctuation of about ±1.7 °C for all levels of drying air temperature. The total capacity of the dryer is about 40 kg of fresh figs producing about 10 kg of dried figs, the calculated operation cost of the dryer approaches about 6.3 LE/kg of dried whole figs fruits. The developed dryer of whole figs fruits showed good mechanical and thermal performance. Stamatios, et al., (2005) studied the drying air characteristics on the drying performance of figs (Ficus Carica) several drying tests have been carried out in a laboratory scale tunnel-dryer. The investigation of the drying characteristics has been conducted in the temperature range of (55 -85 o C) and the air velocity in the range of (0.5 -3 m/s). An Arrhenius-type equation was used to interpret the influence of the drying air parameters on the effective diffusivity, calculated with the method of slopes in terms of energy of activation, and this was found to be insensitive to air velocity values higher than 2 m/s. , mentioned that, application of combined electromagnetic radiation and hot air is gaining momentum in food processing. A combined infrared and hot air heating system was developed for drying of vegetables. A conveyors drying system having three chambers was fitted with mid-infrared (MIR) heaters for radiative heating. Through-flow hot air circulation was also provided for convective mode heating. The system was designed to operate under infrared, hot air and combination mode independently. The performance evaluation studies indicated that combination drying of carrot and potato at 80 o C with air at a velocity of 1 m/s and temperature of 40 o C reduced the drying time by 48%, besides consuming less energy (63%) compared to hot air heating. Combination drying also gave better results over infrared heating alone. The energy utilization efficiency of the dryer was estimated to be 38% for both carrot and potato drying.
This paper presents developments and potentials of solar drying technologies for drying of fruits, vegetables, spices, medicinal plants and fish. Previous efforts on solar drying of fruits, vegetables, spices, medicinal plants and fish are critically examined. Recent developments of solar dryers such as solar tunnel dryer, improved version of solar dryer, roof-integrated solar dryer and greenhouse type solar dryer for fruits, vegetables, spices, medicinal plants and fish are also critically examined in terms of drying performance and product quality, and economics in the rural areas of the tropics and subtropics. Experimental performances of different types of solar dryers such as solar tunnel dryer, improved version of solar tunnel dryer, roof-integrated solar dryer and greenhouse type solar dryers which have demonstrated their potentialities for drying fruits, vegetables, spices, medicinal plants and fish in the tropics and subtropics are addressed. Simulated performances of solar tunnel dryer, improved version of solar tunnel dryer and roof-integrated solar dryers were assessed for drying fruits, vegetables, spices, medicinal plants and fish. The agreement between the simulated and experimental results was very good. The simulation models developed can be used to provide design data and also for optimal design of the dryer components. A multilayer neural network approach was used to predict the performance of the solar tunnel drier. Using solar drying data of jackfruit and jackfruit leather, the model was trained using backpropagation algorithm. The prediction of the performance of the drier was found to be excellent after it was adequately trained and can be used to predict the potential of the drier for different locations and can also be used in a predictive optimal control algorithm. Finally, prospects of solar dryers for drying fruits, vegetables, spices, medicinal plants and fish in the tropics and subtropics are discussed.
Kinetic of Drying of Sliced Fruit with Various Pretreatment Using Cabinet Dryer
2013
The objective of this research is to determine the kinetic of drying on sliced fruit with various pretreatments. The cabinet dryer with electric heater was used in this research. The drying temperatures were 50oC, 60oC, and 70oC. The sliced of pineapple, papaya, and snake fruit were used as samples. Pretreatment involved blanching, osmotic drying and add preservative material. The pretreatment of osmotic drying were conducted for reducing the initial moisture content of the fruit. The result showed that drying time of sliced fruit were about 10 to 24 hours. The osmotic drying has effect on reducing the drying rate. The drying rates at constant period for 50oC, 60oC, and 70 oC of papaya, pineapple and snake fruit were 40.72, 50.75, and 74.43%/h; 28.89, 33.99, and 45.90%/h; 23.97, 31.22, and 42.85%/h respectively. Therefore the activation energies of pineapple, papaya, and snake fruit were 6.6-47.2 kJ/mole, 20.3-45.9 kJ/mole, and 23.9-56.4 kJ/mole. The optimal condition for drying fru...
Performance Evaluation of Solar and Oven Drying for Tropical Fruits
Sretechjournal Publication
Solar drying is the common traditional method to preserve fruits by reducing its moisture content and the microorganisms’ activities, hence, slowing down the mold growth, which affect the quality of fruits. The operational cost of the solar dryer can be cheaper but the drying time using the solar dryer is usually longer than other drying techniques that use electricity due to the lower and inconsistent temperature within its drying chamber. In this work, bananas, papaya and pineapple were dried using an oven at temperatures of 65-85oC, and the results were compared with the outcomes of drying using a simple wood solar cabinet dryer, done in Kota Samarahan, Sarawak Malaysia. The drying profiles for the fruits dried in the oven were found to be quite similar, indicating the insignificant variation in the cell matrix structure of the fruits, and in addition, these results were supported by the small range of the estimated drying constants between 1.32 - 1.83 10-1 hr-1. Moreover, the results showed that the increase in the temperature of drying in the oven from 65 to 75oC did not change the drying time significantly, but the drying time was reduced significantly to 70% when the temperature was increased to 85oC. The fluctuation of temperature and air flow within the solar dryer between 27-34oC and 0.12 -1.52 m/s, respectively, slowed down the drying process, resulting to prolong of drying time. The drying time to reduce the moisture content from 80-60% for the solar drying was between 31 to 74 hours while for oven drying with temperatures of 65-85oC was between 1-5 hours.
Applicability of a single-layer drying model to predict the drying rate of whole figs
Journal of food engineering 81 (3), 553-559, 2007
In this study the mathematical modelling of single-layer drying of whole (uncut) figs (Ficus carica L. var. tsapela) in an experimental heat pump of closed cycle, is presented. A range of drying air velocities (1.0-5.0 m/s) and temperatures (46.1-60°C) were tested in drying whole (uncut) figs to moisture content below 30% w.b. Drying temperatures higher than 50°C, were lay beyond the operational limits of the specific heat pump and therefore a set of auxiliary electric resistances were used. Seven thin-layer drying models were fitted to drying experimental data of figs, implementing non-linear regression analysis techniques. The statistical analysis concluded that the best model in terms of fitting performance was the Logarithmic one. Correlations between the model parameters and the drying conditions to calculate moisture ratio MR in relation to the drying time, were determined and reported.