Modeling for Drying of Thin Layer of Native Cassava Starch in Tray Dryer

Abstract

Purpose:The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of 40-60°C. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between 40-55°C. Drying at 60°C occurred only in the falling rate phase. The critical moisture content was observed in the 40-55°C range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to 60°C. The modified Hii et al. model produced randomized residual plots, the highest R 2 , and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between 40-55°C. The constant drying rate phase occurred without any period of induction over a temperature range of 40-55°C prior to the falling rate period, while drying at 60°C took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

Energy–exergy analysis and mathematical modeling of cassava starch drying using a hybrid solar dryer

“…By taking the average value of the R 2 and RMSE of each model, the Page model was determined to be the most suitable model to describe the drying behavior of cassava starch using a solar tray dryer, followed by the Midilli and Modified Page models. This differs from the thin-layer models of cassava pulp drying using an oven dryer by Charmongkolpradit and Luampon (2017) and a tray dryer by Aviara and Igbeka (2016), who found that the Midilli model and the Modified Hii et al model were the most accurate, respectively. These differences may be attributed to the different drying conditions.…”

“…The values of the intercept (ln(D o )) and slope (E a /R) were −21.925 and −1844.46, resulting in D o and E a being estimated as 3•× 10 −10 m 2 /s and 15.3 kJ/mole, respectively. The activation energy was lower than that observed by other researchers, including Aviara and Igbeka (2016) in their work regarding cassava starch drying in a tray dryer (32.933 kJ/mole) and Shen et al (2011) in their work regarding sorghum stalk drying using an oven dryer (21.4 kJ/mole).…”

Energy Analysis of a Hybrid Solar Dryer for Drying Coffee Beans

“…Table 4 shows the value of effective diffusivity at different drying temperatures. The effective diffusivity values in this experiment are found to be within a range of 10 − 11 to 10 − 9 m 2 /s, which is generally considered the acceptable range for most agricultural and food products (Aviara et al 2016). Another study, performed by Phitakwinai et al (2019), reports that the effective diffusivity values of coffee beans dried at 50°C-70°C ranged from 7.7544.10 − 10 to 1.4525.10 − 9 .…”

Towards an optimal hybrid solar method for lime-drying behavior

“…This is because the water molecules are loosely bind to the lime matrix, which, in turn, makes evaporation easier [59]. The values of effective diffusivity in this experiment are within 10 À11 to 10 À9 m 2 /s, an acceptable range for agricultural and food products [60].…”

“…The activation energy value in this experiment are in the range of generally acceptable value of activation energy for most food products, which is 14.42-43.26 kJ/mol [19]. Several studies have calculated the activation energy during the drying process, such as Aviara and Igbeka [60] in their work regarding modelling of cassava starch in a tray dryer (32.993 kJ/mol), Zhang et al [61] in their work regarding thin-layer modelling of apricot (16.5 kJ/mol), and Shen et al [36] in their work regarding thin-layer drying of sweet sorghum stalk (21.4 kJ/mol). It can be seen that the activation energy value in this experiment is higher compared to those studies, which may be influenced by several factors such as dryer design, operating temperature, and initial moisture content of the food products [36,55].…”