[itsmegame]

Dear members,
I wouuld like to know the model to be used for modelling evaporation of water from a test tube containing water and sand. it would be very helpful if someone guides me in this, by directing me to the governing equations and boundary conditions . i am very new to modelling, im installing matlab currently.
Thank you

[Enthalpy]

Antoine's equation gives the vapour pressure. For instance on Wiki. Provided, of course, that sand is at the bottom hence plays no role.

Then, depending on the setup, vapour diffusion in air, or air movement, can (may well) limit the evaporation speed, and then you're in serious trouble.