Pore network study of bubble growth by vaporisation in a porous medium heated laterally

We present experimental and numerical investigations of vapour phase growth in a two-dimensional model porous medium heated laterally. Visualization experiments reveal the existence of a heat pipe effect within the porous medium when a sufficiently high temperature gradient develops along the porous medium. The bubble growth is characterized by a pattern transition between an invasion percolation (IP) pattern in a first phase of the growth and an invasion percolation in a destabilizing gradient (IPDG) at later times. It is shown that this transition corresponds at the pore scale to a transition between an invasion scenario where only one pore is invaded at each step of the invasion and a multiple pore invasion scenario. The IPDG pattern is characterized by the development of a thin vapour finger, which can explain premature vapour breakthroughs. This type of vapour finger cannot be simulated accurately using traditional models based on the continuum approach to porous media. (authors)