This is my current configuration.
I slid out the end fan, raised the top fan slightly
and slid out the core to give some sense of the
construction.
It all fits together like a Chinese jigsaw puzzle.
The plastic is either press-fit or stitch welded.
Never found any affordable glue for coroplast.
The outer shell is one piece of coroplast, origami-style.
The only tape on the system seals the holes
in the end of the coroplast shell. And duct tape
holds the filter material on the outside end.
I wouldn't even need the tie-wrap if I hadn't
accidentally cut the plastic where I shouldn't have.
This one is 4" square and two feet long. Meets my needs.
No reason it couldn't be arbitrarily large.
I poked it thru a hole in the window because it was easy.
And it saved another right angle bend in the air flow.
I thought about sizing it to fit a square-to-round furnace
duct adapter, but I'm too cheap to spend $7 each
on them.
I keep buying fans and duct work when I find 'em cheap
at garage sales, but I just can't get past "if it works,
don't fix it."
Right now, it's 42F outside, 66F inside and I'm losing
5.9F across the heat exchanger. Meets my 80-20
criteria.
I live alone and don't cook much. Most people
would want more air flow, but this should scale nicely.
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