Determiination of moisture diffusivity in porous media using moisture concentration profiles

Pel, Leo L; Brocken, Hjp Harold; Kopinga, K.

doi:10.1016/0017-9310(95)00201-4

Cited by 96 publications

(79 citation statements)

References 4 publications

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“…8 At least two stages can be distinguished in the drying process. 4,5 In the first stage, the mass transfer at the top surface (zϭ0) is the limiting step in the water transport. As a consequence, only a small gradient in the water saturation ͑m 3 /m 3 ͒ develops and the water saturation can be assumed to be equal to its volume-averaged value, Ϸ͗ ͘.…”

Section: A Starting Pointmentioning

confidence: 99%

“…We limit ourselves to the so-called first drying stage. 4,5 This stage of the drying process covers an important part of the drying process, because approximately 60% of all water evaporates in this regime. This stage has the nice feature that the water remains uniformly distributed throughout the medium, which makes the analysis of the equations simpler.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

How ions distribute in a drying porous medium: A simple model

Huinink¹,

Pel²,

Michels

2002

Physics of Fluids

Self Cite

106

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Salt crystallization at surfaces is an important problem for buildings and monuments. We do not consider the formation of salt crystals as such, but focus on transport properties of ions in a drying porous medium. We deal with the first phase of the drying process, where the water is still uniformly distributed throughout the medium. An approximate model is presented, which accounts for both convection and diffusion. It is shown that the key parameter is the Peclet number at the evaporating surface, Pe≡hL/εD, where h, L, ε, and D are the drying rate, sample size, porosity, and diffusion constant, respectively. When Pe≪1 (diffusion dominates over convection) the ions remain uniformly distributed throughout the system. Strong accumulation at the evaporating surface occurs for Pe≫1 (convection dominates over diffusion). Crossover behavior is found for Pe≈1. Therefore, it is likely that the first crystals will be formed both in the bulk and at the interfaces of the material when Pe≪1. For high values of Pe the density peak at the evaporating surface will reach the saturation concentration long before it is reached in the bulk of the material. As a consequence, the salt starts to crystallize at the interfaces.

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Section: A Starting Pointmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How ions distribute in a drying porous medium: A simple model

Huinink¹,

Pel²,

Michels

2002

Physics of Fluids

Self Cite

106

View full text Add to dashboard Cite

show abstract

“…Some 2D model porous systems consisting of glass beads exist, allowing imaging the drying process using a camera. [13][14][15] To measure fluid distributions inside 3D porous materials, techniques like synchrotron X-ray tomography [16] and nuclear magnetic resonance (NMR) imaging [17][18][19] allow noninvasive probing of moisture with a sufficiently high spatial and time resolution. For this study, NMR imaging was used to monitor the moisture distribution during drying process.…”

Section: Introductionmentioning

confidence: 99%

Transport of a water-soluble polymer during drying of a model porous media

et al. 2017

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This article presents an experimental investigation on transport of methylhydroxyethylcellulose (MHEC) during drying of a model porous material. Nuclear magnetic resonance imaging and thermogravimetric analysis are used to measure water and MHEC transport, respectively. MHEC is added to glue mortars to increase open time, i.e., the time period during which tiles can be applied with sufficiently good adhesion. Previous work showed that MHEC promotes a receding front during drying and therefore leads to differences in the degree of hydration throughout the mortar sample, i.e., the top surface shows poor hydration and the bottom surface shows good hydration. In this study, we investigate the transport of MHEC during drying of a model porous material, consisting of packed glass beads saturated with an aqueous MHEC solution. At MHEC concentration less than 1.3 wt%, homogeneous drying is observed, enabling advective transport of MHEC toward the drying surface. In this case, accumulation of MHEC may form a skin at the top surface and below this skin layer, a gel zone may form, which allows migration of water toward the evaporation surface. When the MHEC concentration is above 1.3 wt%, front receding drying is observed, which prevents transport of MHEC, resulting in a more homogeneous distribution of MHEC. ARTICLE HISTORY

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“…Lemaire et al (2004) analyzed the water transport in expansive clay (from an infiltration test) using the common diffusion equation involving Boltzmann variable. A parameter of hydraulic diffusivity was deduced using the Matano's (Pel et al, 1996) method. After Lemaire et al (2004), two fluid transport mechanisms were involved in the test performed: imbibition of the microporosity in the scale of clay grains and capillary imbibition in the mesoporosity around the clay grains.…”

Section: Discussionmentioning

confidence: 99%

Development of a Large-Scale Infiltration Tank for Determination of the Hydraulic Properties of Expansive Clays

Tang

Cui

et al. 2009

Geotechnical Testing Journal

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A large-scale infiltration tank was developed to study the water transfer in compacted expansive clay. Volumetric water content sensors were buried in a soil column for water content monitoring during infiltration. In addition to water content, soil suction and temperature at various locations and the heave at the soil surface were also monitored. Emphasis was put in minimizing the effect of sensors installation on water transfer and soil deformation. The results obtained for 338 days of infiltration were presented in terms of changes in suction, volumetric water content, temperature, and the soil heave. Based on the recorded data, the performance and limitation of different suction and volumetric water content sensors and the adopted test procedure were analyzed. The recorded data on soil suction and volumetric water content were finally analyzed for determining the unsaturated hydraulic properties of soil, such as the water retention curve and the unsaturated hydraulic conductivity. Note also that the results constitute useful data for further physical analysis or numerical models’ calibration.

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Determiination of moisture diffusivity in porous media using moisture concentration profiles

Cited by 96 publications

References 4 publications

How ions distribute in a drying porous medium: A simple model

How ions distribute in a drying porous medium: A simple model

Transport of a water-soluble polymer during drying of a model porous media

Development of a Large-Scale Infiltration Tank for Determination of the Hydraulic Properties of Expansive Clays

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