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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.

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The objective of this study was to investigate dehydration kinetics of barberry (Berberis vulgaris L.) at different drying temperatures (60 ºC, 70 ºC, 80 ºC), air velocities (0.3 m s-1, 0.5 m s-1, 1 m s-1) with two types of pretreatment. Drying time and colour quality during dehydration were experimentally determined. Barberries were dried from the initial moisture content of 73.44% (w.b.) to the required moisture content of 18% (w.b.). Dehydration kinetics was monitored by measuring barberries weights at regular intervals. Convective drying curves were obtained for the treated and untreated barberries. The effect of two dipping pretreatments on drying kinetics of barberries was also studied. The two pretreatments were thermal shocking by immersing barberries in hot water, followed by cold water cooling, and dipping in olive oil and food grade K2CO3. Colour of the dried product was altered significantly during drying. The results indicated that the use of low temperatures is adequate for preserving this property. The air temperature significantly affected drying time and hunter colour indices of barberries (P< 0.05). With heat shocking and treatment with olive oil and K2CO3, drying time was reduced to about 40% and 60%, respectively. The total colour change (ΔE) and hue angle (H) increased with temperature. Moisture transfer from the test samples was described by applying the Fick’s diffusion model for calculating the effective diffusivity. The effective moisture diffusivity (Deff) of barberry increased as the drying air temperature increased. The Deff values were higher for the treated samples than the untreated ones. These values were also higher for the samples treated with olive oil and K2 CO3 emulsion than those treated with hot water. The effective diffusivity of the untreated and the pre-treated varied between 2.57×10-13 and 9.67×10-12 m2 s-1, respectively. Higher colour change was observed in barberries treated with olive oil and K2CO3 emulsion. Statistical analysis showed that temperature and pretreatment had the most significant effect on drying time at p<0.01.

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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.

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According to the significant effect of the structure and saturation of cathode catalyst layer (CCL) on the operation of proton exchange membrane fuel cell (PEMFC), a pore scale model is presented to simulate the transport processes in CCL. Using this model, the tortuosity and macroscopic effective diffusivity of CCL with different porosities and saturation levels were obtained. The water distribution was obtained by solving two-phase flow equations using volume of fluid (VOF) method. The structure of CCL was reconstructed by assuming agglomerates as equally-sized circles and spheres in two-and three-dimensional domains, respectively. A sequential algorithm was used to determine the location of agglomerates in the computational domain with specific overlap. A comparison was made between the results obtained for three- and two-dimensional domains which showed 2D assumption results in an overestimating on effective diffusivity. However, the variation trend of effective diffusivity versus porosity was about the same. According to the results, due to the blocking effect of water presence in CCL, the increase of saturation causes less available pathways for gas to diffuse. Therefore, the effective diffusivity decreases by the increase of saturation level. Moreover, the decrease of porosity leads to the increase of tortuosity which results in lower pathways for gas to diffuse into the domain and hence less effective diffusivity was obtained. The decrease of oxygen effective diffusivity of CCL causes a lack of oxygen concentration at the electrochemical reaction sites and leads to the decrease of the PEMFC performance.