Drying Granular Solids

Ceaglske, N. H.; Hougen, O. A.

doi:10.1021/ie50331a017

Cited by 103 publications

(52 citation statements)

References 2 publications

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“…Ceaglske and Hougen (1937) first pointed that the Fick's law was not sufficient to describe drying, and that gravity, capillary effects, external pressure were to be taken into account as well. They proposed then to enhance the diffusion theory by considering diffusion coefficients which were function of the water content.…”

Section: Modelling Drying Kineticsmentioning

confidence: 99%

On Water Transfer and Hydraulic Connection Layer During the Convective Drying of Rigid Porous Material

et al. 2014

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The convective drying of a natural porous material, limestone, is investigated in this study, with both experimental and numerical approaches. The first experimental campaign, which focuses on the influence of samples' slenderness, suggests the presence of a hydraulic connection layer between the porous water and the external environment, in spite of the very fine pore structure of the material. This hydraulic transfer enables the fast water evaporation at the beginning of the drying test, when external conditions drive the kinetics. Furthermore, the results show that this layer does not exceed 30 mm deep from the external surface, given the drying conditions of the test. A second experimental campaign aims to analyse, by mean of an X-ray tomography tool, the internal water content during the drying. It confirms that water transfer takes place within the limestone in two distinct stages. The first stage being faster than the second one with a homogeneous desaturation along the sample, it is consistent with the hypothesis of the hydraulic connection layer. Finally, the finite element modelling makes possible to identify the main mechanisms of water transfer, namely liquid convection and vapour diffusion. Keywords

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Section: Modelling Drying Kineticsmentioning

confidence: 99%

On Water Transfer and Hydraulic Connection Layer During the Convective Drying of Rigid Porous Material

et al. 2014

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“…The rate may differ slightly, depending on the texture of the surface. For example, as sand beds dry, the water conforms to the shapes of the particles, so the wet area is larger than the planar one pertaining to the surface of the body, and the rate of evaporation is correspondingly higher (Ceaglske & Hougen, 1937). The distribution of a spreading liquid is illustrated schematically in Fig.6.…”

Section: Dryingmentioning

confidence: 99%

Synthesis and Characterization of Amorphous and Hybrid Materials Obtained by Sol-Gel Processing for Biomedical Applications

Catauro¹,

Bollino²

2012

Biomedical Science, Engineering and Technology

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“…Figures 7-10 show that the diffusion model predicts the drying time but not accurate rate of moisture loss, an observation made by several researchers. [15][16][17] Labuza [18] reported that a diffusion-controlled process will have an activation energy less than 34 kJ=mol. The effective diffusivities determined from these isothermal experiments were plotted on an Arrhenius graph, Fig.…”

Section: Isothermal Drying Apparatusmentioning

confidence: 99%

The Development of an Isothermal Drying Apparatus and the Evaluation of the Diffusion Model on Hygroscopic Porous Material

Roberts

Tong

2003

International Journal of Food Properties

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A drying apparatus combining microwave energy and hot air was developed to dry materials isothermally and its applicability for hygroscopic porous materials has been demonstrated. With on-line sample mass measurements, the apparatus is suitable for determining drying kinetics and investigating the mechanism(s) that limit the drying process for a variety of food materials. Drying curves have been obtained from bread samples using the isothermal drying apparatus. These drying curves were analyzed to compare effective diffusivities calculated from convective hot air conditions (2.35-4.21 Â 10 À9 m 2 =s) to effective diffusivities calculated from isothermal conditions (7.6-18.3 Â 10 À9 m 2 =s), and a significant difference was shown. However, Fick's diffusion equation was shown only to predict drying time and not drying rate. The results of this research showed that proper parameter evaluation did not solve the problem of accurately predicting moisture transfer. Therefore a new model needed to be developed to predict moisture transfer. We hypothesized that during isothermal drying of hygroscopic porous material evaporation is the governing moisture loss mechanism, and Fick's second law was unable to predict moisture loss when this mechanism occurs.

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Drying Granular Solids

Cited by 103 publications

References 2 publications

On Water Transfer and Hydraulic Connection Layer During the Convective Drying of Rigid Porous Material

On Water Transfer and Hydraulic Connection Layer During the Convective Drying of Rigid Porous Material

Synthesis and Characterization of Amorphous and Hybrid Materials Obtained by Sol-Gel Processing for Biomedical Applications

The Development of an Isothermal Drying Apparatus and the Evaluation of the Diffusion Model on Hygroscopic Porous Material

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