DOI: 10.1140/epje/i2002-10106-1
Drying processes in the presence of temperature gradients -Pore-scale modelling
H.P. Huinink1, L. Pel1, M.A.J. Michels1 and M. Prat21 Department of Applied Physics, Technische Universiteit Eindhoven, Postbus 513, 5600 MB Eindhoven, The Netherlands
2 Institut de Mécanique des Fluides de Toulouse, Avenue Camille Soula, 31400 Toulouse, France
h.p.huinink@tue.nl
(Received 16 July 2002 and Received in final form 19 December 2002 / Published online: 11 February 2003)
Abstract
The influence of temperature gradients on the drying of water-saturated
porous networks has been studied. We have focussed on the influence of the
temperature on the drying process via the equilibrium vapor density
, because this is the most sensitive parameter with respect to
variations of the temperature
T. We have used a 2D model which accounts
for both capillary and buoyancy forces. Invasion events by air or water are
handled by standard rules of invasion percolation in a gradient (IPG). Vapor
fluxes are calculated by solving a discretized version of the Laplace
equation. In the model the temperature
T varies linearly from the open
side
T0 to the closed side
TL. The temperature gradients strongly
influence the cluster evolution during the process, because they facilitate
vapor transport through wet regions. When
T0<TL, the movement of the
front is inhibited and dry patches develop after a certain time at the
closed side. When
T0>TL, the front movement is enhanced and the air
ingress in the wet region behind the front is inhibited. The behavior of 3D
systems differs from that of 2D systems, because the point where air
percolates the system and the point where the water network breaks up in
isolated clusters do not coincide. Before the latter fragmentation point the
temperature will mainly influence the drying rates. After this point also
the water distribution becomes sensitive to the temperature profile.
47.55.Mh - Flows through porous media.
68.03.-g - Gas-liquid and vacuum-liquid interfaces.
64.60.Ak - Renormalization-group, fractal, and percolation studies of phase transitions.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002