I was thinking of encasing the dryer tube inside a larger aluminium duct.
You used to be able to get 7" aluminium vent duct for range hoods.
I also thought about dumping the dryer vent into the 7" duct and
running that down the side of my garage. by the time the air hit the
end most of the heat would be transferred out of the pipe.

Thinking a larger box on the inlet side with a screen to capture
lint. and a trap and drain in the low point of the duct if needed to
drain off the moisture.

I don't think it would be too much trouble to maintain and a pretty
easy to install.

just thinking out loud.