oxygen diffusion

[melb]

Hello,

I have a container for growing plants that has a 4 gallon reservoir filled with water. The water level is refilled when it becomes low through a capped tube. Above the reservoir is a grid that allows air to pass through. On top of the grid is a peat-based growing media. The water reservoir is closed to the outside air except for a 0.250" hole.

My assumption is the oxygen diffuses through the grid into the peat based media. My question: is the hole large enough to bring the oxygen level back to 21% after it is depleted and how long will this take?

 

[liberoSimulation]

I think you need to do some work to find out the time taken for oxygen to reach to 21% through this hole.
Unsteady state material balance with proper diffusion model considering the assumptions that might be applicable to your system can be solved by modeling with defined initial and boundary conditions to see the concentration profile across the hole vs the time.

That is my view for your case, and hope that would help.

Regards

 

[melb]

Thanks for the response. One way I could simplify it is let's say we have two 4 gallon tanks connected by a 0.250" diameter hole. One tank has air with 21% oxygen and the other tank has air with 10% oxygen(assume the oxygen has been replaced by carbon dioxide). How do I go about modeling how long it takes for the oxygen to equalize to 21%