Learning Forum

[Pritam singh]

I'm simulating evaporation from a cylinder of 30mm diameter and 3mm height filled with water. Top surface of the cylinder is open and other surfaces are maintained at constant temperature. I want to get temperature profile inside the liquid but the top boundary where phase change and heat transfer is taking place to the ambient, what boundary condition should I give there? Also I'm supplying the liquid from the bottom such that interface level will remain constant. the volume of liquid supply rate is same as evaporation rate of liquid from the top surface. so im finding it difficult to satisfy continuity equation and energy equation simaltaneously.

 

[SRP]

Hi,

To re-create the liquid supply, apply a "Velocity Inlet" boundary condition to the bottom surface. Check that the velocity and mass flow rates are configured to match the pace of your liquid supply.Set the temperature at the intake to match the liquid's original temperature. You can employ a "Pressure Outlet" or "Outflow" boundary condition for the top surface, where evaporation and heat transfer to the environment occur. Typically, the pressure at this boundary should be indicated in relation to the ambient pressure.

Thank you.

 

[Pritam singh]

Hi, 

since on the top surface there is heat transfer by convection and also due to evaporation liquid is converted into vapor. So if I use pressure outlet or out flow boundary condition then i am not able to use these condition at the boundary. For applying these thermal condition at the top surface i considered it as a thin wall and then applied the convection boundary condition along with heat generation (loss of heat at the surface due to phase change), but once i made the top surface as wall then satifying continuity equation is not possible, because we are applying velocity inlet boundary condition so,  that much of fluid must be coming out of our domain and due to wall nothing can come out from the top surface. This is the ambiuity.

[SRP]

Hi,

You calculate the temperature manually at the outlet as per the physics and try to set that temeprature at the outlet. You cam apply convection boundary only at the walls.

Thank you.

[Pritam singh]

Hi,

If I set the temperature at the outlet (for pressure outlet B.C.) then that temperature value is not going to be used for calculation unless there is a backflow. So that input will not fixed the boundary temperature.

Thank you.

[SRP]

Hi,

I suggest you can try creating some region connecting to you outlet and then try to apply bc to the outlet (which is no more a outlet now), you can set temperature condition now and set conditions for the region you created (kind of dummy just for reference). Hope this works.

Thank you.