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Access type: UnknownSubject: search.filters.subject.Moisture diffusivity

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    Mathematical modelling of roselle seeds (Hibiscus sabdariffa L.) drying kinetics
    (2023-08-01)
    Thuy, N. M.
    ;
    Tram, N. B.
    ;
    Cuong, D. G.
    ;
    An, L. T.
    ;
    Duy, H. K.
    Roselle seeds (Hisbiscus sabdariffa L.) are among the seeds that are high in nutrients and can be useful in several applications. Through the drying process, the seeds can be preserved for a long time. The roselle seeds were oven-dried at different temperatures 55, 60, 65 and 70°C, giving different outlet values for yield and final moisture. A total of five empirical mathematical models (Newton, Henderson and Pabis, Logarithmic, Diffusion approach and Page) were selected to describe and compare the drying characteristics of roselle seeds at respective drying temperatures. The adequately suitable drying temperature was found to be 70°C with a drying time of 4 hrs. The effective moisture diffusivity was calculated using the Fick diffusion equation. The results showed that the moisture content of the seeds gradually decreased with time. The effective diffusivity coefficient of moisture transfer varied from 5.4262×10<sup>-10</sup> to 1.074×10<sup>-9</sup> m<sup>2</sup>/s over the temperature range investigated. Mathematical models were fitted to the experimental data and by statistical comparison, the Page model represented drying characteristics better than the other equations with the highest R<sup>2</sup> (0.998) and the lowest values of χ<sup>2</sup> (0.00033) and RMSE (0.00023) observed for drying air temperature of 70°C. The dependence of moisture diffusivity on temperature was described by the Arrhenius equation, with the estimated activation energy being 43.08 kJ/mol within 55 to 70°C. Based on the selected model, it is possible to predict the moisture change during the drying of roselle seeds and thereby better control the process.
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    Effects of germination time and drying temperature on drying characteristics and quality of germinated paddy
    (2015-04-01)
    Chungcharoen, Thatchapol
    ;
    Prachayawarakorn, Somkiat
    ;
    Tungtrakul, Patcharee
    ;
    Soponronnarit, Somchart
    Germination time and drying temperature are very important parameters affecting the quality of the germinated paddy (GP) since the microstructure of starch granules is modified during germination. The experimental results showed that the germination time increasing from 60 to 68 h provided more loosely-packed starch granules, lower hardness of cooked GP, higher γ-aminobutyric acid content (GABA) and larger number of fissured GP after drying. However, the modified microstructure did not cause a difference between drying curves at each germination time. Prediction results of the moisture content from the two-layer model were in good agreement with the experimental results and also showed that the effective moisture diffusion coefficient values of husk were significantly lower than those of germinated brown rice. Drying at a higher drying temperature could reduce the number of fissured GP more significantly. The hardness of cooked GP samples and their GABA contents obtained from drying temperatures changed insignificantly from that of the shade-dried GP. The sensory analysis results revealed that the texture of GP was better than that of the rice without germination and the longer germination time provided the adverse effect on the fermentation odour and texture.
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    Explicit analytical solution for drying kinetics of flat materials
    (2009-02-01)
    Wattananusorn, S.
    This research features a theoretical framework to describe the transport of moisture content in convective drying of flat materials. A new set of formulations is developed on the basis of the spreading-pressure concept as the driving force rather than using the traditional Fick's law. The suggested method also provides a possibility to abandon both conventional isotherms: the two-parameter Brunauer-Emmett-Teller (BET), and the three-parameter Guggenheim-Anderson-de Boer (GAB) models. As a result, the proposed procedure creates a moisture dependent diffusivity embedded in a certain non-linear diffusion equation which can be solved explicitly. © 2009 Pleiades Publishing, Ltd.