Výzkumné centrum: Pokročilé sanační technologie a procesy

Bentonite coupled heat and moisture transport

  • experimental and numerical simulation of bentonite buffer condition: heating from one side and water pressure from the second side
  • coupled process: heat conductivity depends on water content and water retention and diffusivity depends on temperature
  • develepment of own numerical simulation code with object-oriented programming
  • sharing of experimental data in international community (Task force EBS project managed by SKB)

We use an alternative model of water distribution in bentonite, which is appropriate for the situation without contact with liquid water, like the moistrure redistribution driven by heat gradient. Water is assumed to be in two phases, gas (vapor) in the pores as mobile part and sorbed on solids as immobile part. The equilibrium is given by the adsorption isotherm, sorbed water mass ratio as a function of air relative humidity. For the situation without liquid water, this model replaces the standard use of retention curve extrapolated from the case of liquid water and capillary forces.

Illustration of water distribution to the mobile (air) and immobile (bentonite solid grains) zone, with non-equilibrium exchange determined by the adsorption isotherm.
Scheme of the experiment solved in the EBS Task Force project. Position of the temperature sensors.
Fitting of the temperature distribution in the space and time (model versus measurement)
Fitting of the relative humidity distribution in the space and time (model versus measurement)