Mathematical Modelling of the Drying Characteristics of Milled Sorghum Residue

During milling of cereal grains, bran which is separated from the starchy endosperm of the grain is a major by-product. In this study, milled sorghum residue was dried in a cabinet dryer under different conditions (temperature and air velocity). The obtained drying data were fitted into ten existing mathematical models and obtained the best model while, the effective moisture diffusivity and activation energy of the drying process was determined using Arrhenius type approach. The result shows that the initial moisture content obtained for the sorghum residue using standard oven drying method were 41.28 ± 0.33%, 49.52 ± 0.63 % and 47.06 ± 0.42 % on wet basis for the wet residue of variety A, B and C, respectively, at equilibrium point, the final moisture content of about 12.93 ± 0.14 – 14.31± 0.07 as temperature ranges from 40 oC to 70 oC and air velocity ranges from 0.8 m/s to 1.2 m/s. During the drying process, the drying rate falls more rapidly as it was initially high as a result of more moisture in the sorghum residue and the drying rate decreases slowly until reaching the reduced moisture content. The obtained values of effective moisture diffusivity (Deff) ranges between 9.89 x 10-10 and 22.21 x 10-10 m2/s, 9.45 x 10-10 and 20.62 x 10-10 m2/s and 8.56 x 10-10 and 20.76 x 10-10 m2/s for variety A, B and C, respectively. However, the result of the modelling shows that the drying characteristics of variety A and B of the sorghum residue can be predicted using Midilli et al. model while the drying behaviour of Variety C can be predicted using Hii et al. model.

Determination of moisture diffusivity and activation energy on fixed bed drying of red pepper (Capsicum annum) on convective solar drying

Moisture diffusivity and activation energy are two important variables in a drying process to understand a certain product's drying behavior. This study aimed to determine the value of effective moisture diffusivity and the activation energy of red pepper in a conventional forced convective drying based on electricity (conventional convective drying/CCD) and forced convective drying based on solar energy (convective solar drying/CSD). The value of effective moisture diffusivity was determined using the equation, which refers to Fick’s second law. The Arrhenius equation determines the activation energy value as a model of the relationship of inverse temperature and the normal logarithmic value of effective moisture diffusivity. The results showed that the values of effective moisture diffusivity of CCD 70 °C were the highest. The regression analysis between the drying layers (X), and effective moisture diffusivity (Y) showed a polynomial pattern with a coefficient determination R2 value of 0.85 (CCD 70 °C), 0.81 (CCD 60 °C), 0.88 (CCD 50 °C), and 0.48 (CSD). (R2) The higher moisture diffusivity values in CCD indicated that the drying systems are more stable than CSD. The drying activation energy calculation showed that the value of CCD's activation energy was 36.36 kJ/mol.K, while the value of CSD's activation energy was 31.28 kJ/mol.K. Those results were consistent with the results of the previous studies.

Kinetics, energy efficiency and mathematical modeling of thin layer solar drying of figs (Ficus carica L.)

First convectional thin layer drying of two fig (Ficus carica L.) varieties growing in Moroccan, using partially indirect convective dryer, was performed. The experimental design combined three air temperatures levels (60, 70 and 80 °C) and two air-flow rates (150 and 300 m3/h). Fig drying curve was defined as a third-order polynomial equation linking the sample moisture content to the effective moisture diffusivity. The average activation energy was ranged between 4699.41 and 7502.37 kJ/kg. It raised proportionally with the air flow velocity, and the same pattern were observed for effective moisture diffusivity regarding drying time and velocity. High levels of temperature (80 °C) and velocity (300 m3/h) lead to shorten drying time (200 min) and improve the slices physical quality. Among the nine tested models, Modified Handerson and Pabis exhibited the highest correlation coefficient value with the lowest chi-square for both varieties, and then give the best prediction performance. Energetic investigation of the dryer prototype showed that the total use of energy alongside with the specific energy utilization (13.12 and 44.55 MWh/kg) were inversely proportional to the velocity and drying temperature. Likewise, the energy efficiency was greater (3.98%) higher in drying conditions.

Experimental Investigation to Evaluate the Effective Moisture Diffusivity and Activation Energy of Cassava (Manihot Esculenta) under Convective Drying

Investigation of effective moisture diffusivity (Deff) and activation energy (Ea) of cassava were conducted under convective drying at temperature and velocity of 60, 70 and 80 °C, and 1.0, 1.5 and 2.0 m/s, respectively. In the experiment, cassava was sliced into 3 mm-thickness and dried under given conditions until mass was saturated. Deff and Ea were described by Fick’s second law and Arrhenius-type equation, respectively. The experimental results indicated that the increase in Deff was significantly affected by increasing the hot air temperature and velocity. The slope method was used to calculate average Deff, and results were found to range from 3.83 × 10–9 – 9.86 × 10–9 m2/s. The Ea was found to decrease with an increase in hot air velocity, ranging from 21.23– 24.92 kJ/mol. Additionally, Moisture content (Mw) and Drying rate (DR) were also used to describe the drying kinetics. From the experimental results, Mw and DR decreased with an increase in drying time. DR increased with an increase in temperature and velocity causing Mw to rapidly decrease and drying time to reduce. The highest DR was found to be 0.55 gwater/min at temperature of 80 °C and velocity of 2.0 m/s.

EFFECT OF DRYING KINETICS ON THE QUALITY OF THE GREEN CAPSICUM

The effect of power (Watt) of microwave assistance drying on consumption of energy, drying efficiency and kinetic studies in green capsicum (Capsicum annum) was studied. For describing green capsicum drying behavior two mathematical models (Lewis model and Parabolic model) are used. Based on their root mean square error, χ2 and R2, values of predicted and experimental moisture content to models are compared. The drying time of green capsicum was decreased from 47 minutes to 22 minutes due to increasing power of microwave from 180 Watt to 900 Watt. The drying process was showing a falling rate period. In Lewis model the result shown most appropriate model for the study. For co-relation of moisture content with effective moisture diffusivity a third-order relationship was found. The effective moisture diffusivity of Green Capsicum samples increased as the moisture content decreased. Over the microwave power spectrum tested, the effective diffusivity ranged from 1.5 X 1012 m2/sec to 4.3 X 108 m2/sec, with an energy activation of 31.74 W/g. As microwave power and moisture content increased, so did energy efficiency.

Evaluate the drying of food waste using cabinet dryer

Purpose In order to reduce leachate from food waste; a food waste dryer with a conventional tray was built, and drying of food waste was investigated. Methods Power of 2.7 kW was used as the heat source, and a centrifugal fan with an air volume of 1300 m3/h, 2800 rpm, and 110 pa was used. The experiments were performed at three temperatures of 50, 60, and 70°C and three air velocities of 1, 1.5, and 2 m/s with a thickness of 3 cm. A conventional tray was used for drying. The Drying kinetics, effective moisture diffusivity, activation energy, and dryer energy consumption during drying of food waste were obtained. Result The minimum drying process was occurred in temperature of 70°C and air velocity of 2 m/s at the 120 min, and the maximum drying process was happened in temperature of 50°C and air velocity of 1 m/s at the 890 min. The energy consumption of drying process had the lowest value at 70°C of temperature and 2 m/s of inlet air velocity. The highest energy consumption value was related to temperature of 50°C and velocity of 1m/s. Effective moisture diffusivity of waste food during the drying process was in the range of 2.74×10− 9-3.65×10− 8 m2/s. The values of energy of activation were determined between 21.596 and 64 KJ/mol. Conclusion Cabinet dryer with a conventional tray can be used for drying food waste in the shortest time with low energy consumption.

EFFECT OF DIFFERENT TEMPERATURE ON REHYDRATION KINETICS OF CHICKEN BREAST MEAT CUBES

In the present research, it was aimed to understand the effect of different rehydration temperatures (80, 90 and 100°C) on rehydration kinetics of hot air dried chicken breast meat cubes. The rehydration rate increased with the increasing of temperature of rehydration water. ΔE and chroma values of the rehydrated samples at 90°C and 100°C samples were found statistically similar. To describe the rehydration kinetics, four different models, Peleg’s, Weibull, first order and exponential association, were considered. Between these four models proposed Peleg’s model gave a better fit for all rehydration conditions applied. The effective moisture diffusivity values of chicken meat increased as water rehydration temperature increased.