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by schneems 545 days ago
Thanks for mentioning that. It seems the PDF and the google docs "manual" have diverged a bit. (at least in page numbers).

I was curious about materials for the core. I know that they're supposed to exchange humidity as well as heat. I know PLA will absorb and release water but I would guess it wouldn't transfer enough to be very efficient. Though I would be happy to be wrong.

I assume the Core in my Panasonic whisper comfort was made out of something more permeable than "simply" extruded plastic. (would love to know more if someone has details).
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open_erv2 545 days ago
The MPLA (not pla) does not absorb the water vapor, but it condenses on the plastic and then evaporates. There is also the option of sorbent, which grabs the water vapor and then releases it with each cycle, before condensation occurs, getting higher efficiency.

The material in the whispercomfort is IIRC a fiberglass paper. It can only transfer liquid water, not solid water, and not vapor, effectively. The water condenses, whets the paper, then evaporates out the other side. It's a reasonable approach but does not work well in very low temperatures, and also the condensation process implies certain limits to efficiency, same as a non sorbent coated regenerative heat exchanger. The water doesn't start to condense until 100% RH, so it is 100% when it leaves the exchanger, while the air coming in is lower than that, usually. Thus water is lost.

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NavinF 545 days ago
Very interesting! Do you have a method of adding sorbent to a 3d print?

I wonder if it'd be worth having three TW4 modules with sorbent on only one of them. That way you can control humidity better by choosing 2 of the 3 to use at a time. Eg after a long shower you might wanna discard water vapor for an hour

What's the significance of the model numbers 4 and 12?

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open_erv2 545 days ago
Yeah that would probably work, it's just a matter of cost. A lot of people balk at $700 CAD, the eventual price is supposed to be $1300 for a pair, you do that and you are looking at a lot of $ for the flow and energy recovered.

The numbers are the number of versions before it stabilized, so 12 tries for the window mount, 4 for the through wall. It took a while.

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