jamromhem
Ya, you have a good point. I briefly thought about allowing the upper chamber to drain down into the bottom one, but didn't want the air between the two chambers to be allowed to mix. That would reduce the effectiveness of the system, as well as divert the airflow from where it's supposed to be going. But after reading your post, I thought I could add a sort of vent (through hole, bulkhead fitting etc.) and small tube to drain it down the outside of the 55 gallon drum into the sand the whole thing will be sitting on. Or even just cut some small slits or drilling tiny holes in the bottom sides of the upper chamber for the water to drain through (perforating it).
As for the fan, I will be using a 6 inch inline duct fan like this one :
6" Aero-Flo InLine Duct Fan 240 CFM - Airflow Technology, Inc. (Note: it states "Great for Greenhouses and Hydroponic gardens") so it will be OK in high humidity situations.
I wont be buying it online, but getting it at Lowe's or Home depot so I don't need to pay for shipping. It may not be that exact manufactures fan, but it will be a 6 inch duct fan with about a 240-250 cfm rating, and for use in humid conditions (like greenhouses or bathroom duct vent fans). That's why the warm air inlet tube (that extends up from the 55 gallon drum) is 6 inches wide, that way the 6 inch inline duct fan will fit inline with it seamlessly, and without restricting any airflow.