Greg wrote:

I am looking for something a little more efficient than a clothes line.
Has anyone seen plans for some closed loop dryer that can cope with the
RH you see in the sub tropics?

How about a little greenhouse? Hang a piece of plastic over an EW line
between two poles, then string another line below it. Leave the ends of
the tent mostly open.

How open? If they are completely closed, the water vapor never escapes.
If they are completely open, the greenhouse adds nothing, compared to
a clothesline.

Don Ocean and and PJM are also invited to answer this hvac science and
engineering question. Please compare the drying rate to an outdoor
clothesline and include the effects of condensation, if anticipated.

For the sake of definiteness, if Greg wants to remove 12 pounds of water
from 12 pounds of clothes with 400 ft^2 of surface (both sides) in minimal
time in full sun in August in Key Largo, when it's 84 F and w = 0.0185,
using a 16'x16' R1 greenhouse with 90% solar transmission, how many cfm
of outdoor air should flow through the greenhouse?

Nick