Figure 1

Porous medium made of 257 (±9) μm sodiocalcic glass beads packing (from CVP Abrasif & Broyage, cleaned with NaOH and de-ionized water, volume fraction: 60.3$\%$) homogeneously filled with a coffee suspension (3.5$\%$ weight in water) before (a) (beads, water, coffee) and after (b) (beads, coffee) drying under natural room convection and ambient temperature.Reuse & Permissions

Figure 2

Drying through the upper free surface of a cylindrical (height $=$ 4 cm) porous medium made of glass beads (62$\%$ volume fraction) initially filled with a colloidal suspension at 5$\%$ volume fraction in water. Drying occurs through the upper surface (right) with a steady dried air flow at 0.1 m/s leading to an initial drying rate of $1.1\times {10}^{-10}$ m${}^3$/s which corresponds to a drying velocity (see text) of $1.2\times {10}^{-7}$ m/s. MRI measurements were carried out every 2 h over 4 days giving us access to (a) the distribution of particles in the pores at the end of the experiment [the black line corresponds to Eq. (4) (see text)], (b) the distribution of colloids in the liquid phase, and (c) the distribution of water as a function of sample height. For the two last panels the profiles displayed are separated by 10 h. Red thick lines represent the initial state.Reuse & Permissions

Figure 3

Scheme of the drying mechanism in a porous medium coupled with the transport of colloidal particles. The green (light gray) particles are free to move in the liquid phase whereas the red (dark gray) ones are motionless in the compacted region. Initially (a) the particles are homogeneously dispersed in the medium and water saturation is at its maximum. Then the particles start to accumulate around the free surface of the sample (b). Afterwards the particles start forming a crust (c) and the saturation decreases in the whole sample. At the end of drying the compacted region extends throughout the sample but with an effective particle content decreasing downwards.Reuse & Permissions

Figure 4

Total water saturation (ratio of the total mass of water to the initial mass of water) as a function of time during the drying of a porous medium. Initially filled with (black, bottom) pure water, [red, (dark gray)] 5$\%$ colloidal particles in water, [green (light gray)] 10$\%$, (blue, upper) 15$\%$. The square symbols correspond to the experimental data. The dotted lines correspond to the modeling approach based on the measure of the compacted-front thickness, and the continuous lines to the full modeling approach.Reuse & Permissions