Evaporation Rate from Tank Vent

[pflow]

Please inform me of a method and equation to calculate the evaporation rate of water out the vent of a storage tank. The tank is 6 ft diameter and 8 ft tall with a 4" vent on top.

I have found many equations for water pools, but I think this situation is different (small opening on large covered pool).

 

[MortenA]

Is it a aboveground vessel?

Imo it will depend on thermal cycling.

When the content get heated it breathes (worst case suturated) air out - when it get cold is breathes (worst case dry) air in.

If the vessel is in open air then the air may get heated during the day an cool during the nigt.

Set up a spreadsheet for worst case (almost empty tank etc)

Best regards
Morten