Learning Forum

[801842]

I've been trying to simulate a close container with liquid water and air on it with the objective of reach the equilibrium ratio of vapor water on the air at a certain constant temperature below the saturation temperature by diffusion forces.

I've try to use the multiphase model with the mass transfer mechanism from water liquid to wet air (mixture of air + vapor water) with a tabular pt sat properties and the species model (species transport) active, applying inlet diffusion at the wet air phase but it doesn't seem to be evaporating, it just expand the area where the liquid water is located but without any evaporation. What may I change to reach my objective or what should I use?

Thank u!

[Rob]

If the domain is closed what boundary are you setting for diffusion?  Species transport is typically used for non-evaporating systems, so you may want to review the options in Fluent. 

[801842]

I was trying to do the equilibrium inside the container, so the walls of the container don't let the water or air pass throw. The limit of vapor in the air must be given by the saturation pressure at the specify temperature, what I thought I define in the tabular pt sat I set at the saturation properties, in the evaporation/condensation mass mechanism

[Rob]

OK, that makes more sense. What is the vapour density?

[801842]

The vapor density is 0.01284 kg/m^3 corresponding to the temperature that I set up (15 ºC) and density of the phase wet air (air + water vapor) is calculated by the volumen-weight-mixing-law.

[Rob]

OK, so as the water evaporates where does it go? Consider the CFD model as opposed to "physics". 

[801842]

It is supposed just to mix with the air of the container. I was trying to simplify the problem, later I will partially open the container so that the water evaporated can be spread and the water liquid can continue the diffusion and evaporation till there is no water left at the container. 

[Rob]

Closed domain may well be harder as you also need to compress the vapour. Otherwise as liquid water becomes vapour where does it go?

[801842]

Okey, thanks I will try opening the container.