Showing 15 results for Drying Kinetic
Volume 11, Issue 3 (7-2009)
Abstract
This paper peresents a mathematical model for the thin layer drying of the Viliamz cultivar of soybean. The thin layer drying behaviour of soybean was experimentally investigated and the mathematical modelling performed by using thin layer drying models provided in the literature. Experiments were conducted at inlet drying air temperatures of 30, 40, 50, 60 and 70ºC and at a fixed drying air velocity of 1 m s-1. Thirteen different thin layer mathematical drying models were compared according to their r values, RMSE, 2 and EF by non-linear regression analysis. The effect of drying air temperature on the model constants and coefficients was predicted using multiple regression analysis. According to the results, the Midilli et al. model was found to be the best mathematical equation for modelling thin layer drying of soybean.
Investigation of energy consumption and Drying Kinetics of thyme leaves in microwave dryer
Khafajeh, H. 1, Banakar, A. 1 , Minaei, S. 1, Taghizadeh, A. 2, Motavali, A. 1, Rezaei Aderyani, M. 3
Volume 11, Issue 45 (3-2014)
Abstract
In this study the effect of microwave power on drying behavior, effective moisture diffusion, the best mathematical model of drying, activation energy values and energy consumption of the herb thyme was investigated. Results of regression analysis of mathematical models in MATLAB software points that the Midili model has the best described to the data. Effective diffusion coefficient of herb thyme was found to be between 15.416 and 213.802m2/s. Also the activation energy was determined to be 84.86 W/g for constant drying rate and 100 W/g for effective moisture diffusion. In addition, the minimum and maximum value of specific energy consumption drying of herb thyme was 6.994 to 19.607 kW/kg, respectively.
Volume 13, Issue 2 (3-2011)
Abstract
Drying characteristics of Quercus were determined experimentally as a function of temperature, air velocity, and variety (Quercus Persica and Quercus Libani). In order to estimate and select a suitable drying curve, five different thin layer drying models were fitted to the experimental data. Experiments were performed at the air temperatures of 50, 60 and 70°C. At each temperature level, two air velocities were adjusted: 0.5 and 1m/s. The effect of air temperature was found to be significant in comparison to air velocity for drying of fresh Quercus fruits. Increasing air velocity at constant air temperature resulted in the decrease of drying time. Among all the selected drying models, the Page model was found as the best mathematical model for describing the drying kinetics of Quercus fruits. Based on the results, drying temperature of 70 oC and air velocity of 1 m/s are the optimum values for drying Quercus fruit. Drying time and Page model constants were found to be dependent significantly on the variables studied.
Volume 13, Issue 5 (9-2011)
Abstract
The objective of this study was to investigate the drying kinetics of oyster mushroom, Pleurotus ostreatus Mushrooms were dried using a cabinet-type convective dryer. Air temperatures of 50, 60 and 70 oC were used for the drying experiments. The experimental drying data were fitted to different theoretical models to predict the drying kinetics. Nonlinear regression analysis was performed to relate the parameters of the model with the drying conditions. The performance of these models was evaluated by comparing the correlation coefficient (R2), root mean square error (RMSE) and the chi-square (χ2) between the observed and the predicted moisture ratios. Among all the models, the model of Midilli et al. was found to have the best fit in this study. Effective moisture diffusivities (Deff), diffusivity constant (D0) and activation energy (Ea) were calculated. The Deff varied from 9. 619x10-10 to 1.556x10-9 m2s-1 over the temperature range studied and Ea was 22.228 kJ mol -1.
Volume 13, Issue 53 (5-2015)
Abstract
Drying is one of the preservation techniques in which moisture removal through simultaneous heat and mass transfer occurs. Due to low energy efficiency and prolonged time of hot air drying, the new drying techniques such as infrared, must be employed. In this study, the effects of temperature and drying method on the kinetics of persimmon slices with 5 mm fixed thickness were investigated. The tests were performed at 3 temperature levels (50, 60 and 70◦c) using both hot air and infrared dryers in 3 replicates. The experimental data obtained from drying treatments were fitted to 9 mathematical models in order to evaluate the drying kinetics of persimmon slices. The fitting quality of the proposed models was evaluated using the coefficient of determination (R2), root mean squares error (RMSE), chi- square (χ2) and sum square error (SSE). Based on the results, Wang and Singh model was found to be the best model fitted to the experimental hot air drying data at all temperature levels. In the case of experimental infrared drying data at 50 and 60◦c, the logarithmic model showed the best fitting results while at 70◦C, 2-term model showed the highest fitting quality. These models exhibited the highest value of R2 and the least RMSE, χ2 and SSE comparing to the other models
Volume 13, Issue 54 (8-2015)
Abstract
Pistachio plays an important role as exportation of Iran. The method of drying process has a remarkable influence on the quality of dried products. There are various methods for drying pistachio; however, choosing a suitable method of drying depends on reliability, healthiness and rapids. In current research, the effect of temperature in three levels of 40, 50 and 60°C and rotational speed of the dryer agitator in three levels of 5, 10 and 15rpm on reduction rate of drying period and drying kinetics of a common Iranian pistachio (Kalleh Ghoochi v.), in a new intelligent- vacuum rotary dryer, was investigated. This dryer was consisted of a cylindrical chamber and a twin electrical heater which dried products in a vacuum medium. The experimental data was analyzed in a statistical software "SPSS 10 " In accordance with the results, temperature and rotational speed of the agitator had a significant effect on drying period. When temperature and speed were 60°C and 15rpm respectively, drying period was short and equaled 185 min, but in temperature of 40°C and speed of 5rpm, drying period was long and equaled 325 min. Increasing the temperature also increased the rate of drying significantly. Results indicated that increasing temperature from 40°C to 50°C caused 25% decrease in the drying period and increasing temperature from 40°C to 60°C caused 39% decrease in drying period.
Volume 13, Issue 56 (10-2015)
Abstract
In this study, pomegranate arils were dried by infrared dryer to find a suitable mathematical model, effective moisture diffusion coefficient and activation energy. The experiments were performed at four air velocity levels (0.3, 0.5, 0.7 and 1 ms-1) and three infrared radiation levels (22, 31 and 49 W cm-2). Experimental data with semi-theoretical and empirical models were evaluated to find the best model. Among the models, Midili's Model was selected based on R2, χ2 and RMSE criteria. Effective diffusion coefficient of pomegranate arils was in the range of 0. 4×10-9 to 3.21×10-9 m2 s-1. Activation energy was calculated by using Arheneus exponential model. The values of activation energy were determined in first method between 0.43 to 1.17 W g-1 cm-1 and second method between 1.1 to 0.72 W g-1 cm-1.
Volume 14, Issue 3 (5-2012)
Abstract
Vacuum drying of Salicornia herbacea L. was performed at different drying temperatures (50, 60, 70, and 80C) to evaluate the drying characteristics and the effect of drying temperatures on the quality of Salicornia. As the drying temperature increased, the drying time decreased significantly (P< 0.05). The drying rate decreased with decrease in moisture content and increase in drying time. On the other hand, the drying rate increased with increase in drying temperature. The logarithmic model exhibited the best fit to the experimental drying data among the tested models. The drying constants estimated using the logarithmic model were found to be affected by the drying temperature. The activation energy for drying was 15.02 kJ mol-1. The surface color of the Salicornia herbacea samples was significantly affected by the drying temperature (P< 0.05). CIE L*-, b*-, and Chroma (C*)-values increased significantly, while a*- and hue angle (h*)-values decreased significantly after drying at all of the drying temperatures (P< 0.05).
Volume 16, Issue 96 (1-2020)
Abstract
The purpose of this study was to produce red beetroot pulp powder using foam-mat drying technique and to investigate the effect of foam thickness on drying kinetics and physicochemical and microstructural properties of the resulting powder. To prepare foam, ovalbumin as foaming agent at a concentration of 2% (w / v) was added to the red beetroot pulp and was stirred for a specific time and speed. Prepared foam was spread on aluminum plates at thicknesses of 5, 6 and 7 mm and then dried in a hot air cabinet dryer at 50 ºC and constant air velocity of 1 m/s. Results showed that increasing foam thickness from 5 to 7 mm had no significant effect on moisture content and moisture ratio but significantly (p <0.05) reduced the drying rate by about 29.63%. The effective moisture diffusion coefficient was significantly affected by the foam thickness and ranged between 5.550 × 10−9 and 7.388 × 10−9 m2/s. Also, with increasing foam thickness, due to increasing drying time and more denaturation of proteins, an increase in Carr index and Hausner ratio was observed, resulting in a decreasing trend in the flowability of the powders. Bulk and tapped densities of powders were significantly decreased due to the change in moisture content, caused by the increase in foam thickness. Thickness had no significant effect on water solubility index and water absorption index. The microstructure analysis of the produced powders by field emission scanning electron microscope showed that with increasing foam thickness, cracking and surface roughness of powder particles increased. The results of this study and further studies can lead to optimization of red beetroot powder production as a natural food coloring and better preservation of its nutritional and functional properties.
Mohsen Heydari, Khalili Khalili, Seyed Yousef Ahmadi Brooghani,
Volume 17, Issue 8 (10-2017)
Abstract
Drying process is one of the intensive energy operations in many industries such as tile and clay brick manufacturing industries. Cracking as a result of non-uniform deformation is one of defects that may occur during drying making the dried products useless. Intermittent drying is an effective strategy for improving the drying kinetics and the quality of the dried parts. Proper selection of intermittent drying parameters including the period, amplitude and the start time of variation are the main challenge in the drying. The purpose of this paper is to examine the effect of the period of temperature variation on the drying kinetics and induced stresses in the intermittent drying of clay like material. 3D modeling and simulation of continues and intermittent drying has been done by using finite element method. Moisture and thermal stresses are compared with each other. The good agreement between experiments and the simulation results revealed that the model developed is valid and accurate. Simulation results show that the stresses induced by drying heavily influenced by the frequency of variation. The change of the Frequency variations depending on the material properties and sample dimensions can decrease/increase the drying induced stresses. Intermittent drying has a different effect on the different points of the samples. Hence, the points susceptible to crack formation must be investigated simultaneously. The thermal stresses are negligible compared to the moisture stresses and can be neglected in drying modeling.
Volume 18, Issue 110 (4-2021)
Abstract
Allium stipitatum is one of the most important plants native to Iran, which has a special position in food basket of people because of its many healing properties. In this study, effect of a proposed combined microwave-hot air method on kinetics and physical properties of Allium stipitatum was investigated. In the proposed method, after applying microwaves (600, 750 and 900W), samples were subjected to combined microwave-hot air drying process. Results showed that Logarithmic model with values of R2 =0.996 and RMSE=0.002 was the best one to model drying kinetics of Allium stipitatum slices under the proposed method. In addition, drying curves analysis showed that the more microwave power, the less drying time and the more process rate. Moreover, in the combined section, effect of microwave power will be dominant due to higher energy. The optimum operating point to achieve the lowest moisture content and drying time ocuured at primary power of 900W and combined conditions of 450W at 80°C. Increasing microwave power increased effective moisture diffusivity from 0.167×10-8 to 0.283×10-8 m2/s and decreased average activation energy from 17.429 to 2.074 kJ/mol. The optimum operating conditions in terms of appearance quality (colorimetry) were related to drying at microwave power of 900W and combined conditions of 450W and 80°C, which was introduced as proposed optimum point. In general, the proposed combined method compared to microwave method alone, was an efficient method in ordrt to keep the product quality characteristics and its use in drying Allium stipitatum is recommended.
Volume 18, Issue 119 (12-2021)
Abstract
In this research, a combined photovoltaic / thermal solar dryer containing phase change materials (PCM) was designed and fabricated for drying mint leaves. The performance of this dryer was evaluated under the climatic conditions of Mashhad city with a longitude of 59.62
and a latitude of 36.26
. The components of this dryer mainly include: photovoltaic panel, solar collector, blowers, phase change material chamber containing paraffin wax and drying chamber. Solar dryer and natural drying in shade as two different drying types were used to perform experiments on mint leaves. The initial moisture content of the mint leaves was 80% which reduced to 12%. The required drying time for the combined solar drying and natural drying was 290 minutes and 1560 minutes, respectively. Eight thin layer drying models available in the literature were fitted to the experimental data in which the Two-term model and the Wang and Singh model were the best fit models for natural and combined solar drying respectively. These models have the highest correlation (highest coefficient of determination and least root mean square error and Chi-square) with the experimental moisture ratio among the other models.
Volume 20, Issue 134 (4-2023)
Abstract
The aim of this research was to investigate the effect of basil, sage and chitosan edible coatings on the physicochemical properties of microwave-dried apple slices. In this study, apple fruit slices were coated with basil, sage and chitosan in three concentrations (0, 0.5 and 1%) and dried at different microwave powers (90, 180 and 360 W). The drying kinetics, color, texture and antioxidant activity of apple slices were investigated. The analysis of the data indicated that the drying of the apple slices happened only in the range of the descending speed period. These data were fitted with 7 different experimental models, among the models, the most suitable models for basil, sage and chitosan coatings were Midili, Approximation of diffusion and Verma, respectively. Midili was able to predict moisture content more accurately than other models. Also, the amount of brightness, adhesivenes, cohesiveness and antioxidant activity increased with the increase of coating concentration and microwave power, but the amount of redness, yellowness, browning, general color change and hardness decreased. In general, edible coating is one of the new methods that increases the shelf life and quality of the final product. Therefore, it is recommended to treat fruits using edible coatings to increase the appearance quality and improve the color at the end of the drying process.
Volume 21, Issue 5 (9-2019)
Abstract
In this work, performance of a newly designed hybrid dryer was investigated. Drying was done with the support of solar energy to microwave conveyor dryer. By using collector, which was designed with semisphere shape for having high efficiency from solar energy, hot air was produced and moved through the tunnel with velocity of 3 m s-1 and by using 0.7, 1 and 1.4 kW microwave support, drying behavior of 5, 10, and 15 mm zucchini slices were examined. At the end of drying process, drying time, color changes of dried products, energy consumption, collector efficiency, and modelling of drying were determined. Considering the time required for drying the zucchini slices until reaching 10±1% (wb) moisture content and electrical energy consumption values, the most suitable results were obtained from 1 kW microwave power, air velocity of 0.245 m min-1, and 5 mm zucchini slice thickness, corresponding to total energy of 1.143 kWh. The collector efficiency was calculated as 24.3%, under the environmental conditions of our study.
Volume 25, Issue 2 (2-2023)
Abstract
The present study was conducted to dry apples in a Temperature-Controlled Microwave (TCM) drier under optimum conditions. Drying durations, drying curves, color changes and drying models were analyzed. Within the scope of this study, TCM drying, oven drying, shade and sun-drying methods were experimented. Apples were sliced into four and eight pieces and dried at 50, 60 and 70°C drying temperatures in three replicates. The shortest drying time (30 minutes) was achieved in temperature-controlled microwave drying and the longest drying time (287 hours) was observed in shade-drying method. TCM drying best preserved the color parameters. Lightness and redness values were best preserved with TCM drying at 70°C in four slices and yellowness value was best preserved with again TCM drying at 50 and 60°C temperatures in four slices. Chroma values were best preserved with temperature-controlled microwave drying at 50°C in eight slices. Considering the drying durations and color parameters, TCM drying was identified as the best method for drying apple.
