My Toy HRV runs the air straight thru the coroplast
channels, but the open layers have side-exit at each end.
That should give some turbulence to the flow.
A relatively easy experiment is to cut some coroplast strips just
wide enough to be mechanically stable and insert them
off-angle into the open channels. That oughta add significant
turbulence without reducing the surface area much.
Poke a pair of thermocouples down into the one channel
and see what difference it makes.
A/C has some machine-cut black coroplast squares.
Maybe we can convince him to do the experiment.
FWIW, some recent construction plans for HRV have a block
down the center of the open channels and a reversal space
at the end. They run the air down one half and back up the
other. That gives some temperature gradient that has some
of the benefits of a full counter-flow exchanger. And it's
easier to route the ports.
I have a very crude thermal imager that was made for firemen
to find cold bodies in a flaming building. It won't focus up
close, so may not yield useful results, but next cold spell,
I'm gonna break it out and see if I can learn anything
about the thermal profile from the outside of the exchanger.
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