DIY ventilation heat exchanger

[AC_Hacker]

Originally Posted by Daox

Do you have any examples of the 180 degree flowing design?

Daox,

I tried to find the links when I did the post, but couldn't find the web site again.

Sometimes I find material that is very interesting but not relevant to an original search. I try to bookmark as much of these surprises as I can, but some just get away. I think that's how it is with the Internet.

As I recall, the increase in efficiency for the 180 degree counter flow was small (5% to 8%). The 90 degree design seems to dominate the market, my guess is that it is pretty efficient and easy to make.

For me, the lesson to be learned is that China is making the cross-flow cells and selling them to OEMs. If we can discover the source of the cells, we can build the box ourselves.

But effectively utilizing an energy recovering ventilating system is predicated on having a home that is very tightly sealed...

This gets us back to insulation and sealing... Talk about 'all roads lead to Rome', here we are again.

Regards,

-AC_Hacker

P.S.: BTW, don't know if you saw my post on Grey Water Energy Recovery, that one is not dependent on having a tight house.

* * *

[Piwoslaw]

Originally Posted by AC_Hacker

As I recall, the increase in efficiency for the 180 degree counter flow was small (5% to 8%). The 90 degree design seems to dominate the market, my guess is that it is pretty efficient and easy to make.

For me, the lesson to be learned is that China is making the cross-flow cells and selling them to OEMs. If we can discover the source of the cells, we can build the box ourselves.

From what I read somewhere, the cross flow's efficiency is around 60%-70%, while the counter flow can get over 90%, so that may be worth fighting for. I think the differences in our sources come from different designs being tested.

I'm all for finding a source of cheap cross flow cells. Using 2 or 3 to make a counter flow set up (like in the picture in my second post) would give killer efficiency. I tried googling in both English and Polish for just the guts, but no luck, only "recuperators with alu cell". I'll ask at a local builder's forum.

Re heat pump: In my climate it's very hard to find an old A/C unit, air conditioning is just starting to be mainstream. Old refrigerators, now that's a different story. I can find one in any town, or even in any roadside ditch or forest:/ On the other hand, taking a fridge apart is illegal in Europe (environmental protection laws), so hush-hush

EDIT: I found this page on different types of heat exchangers. It's in Polish, but maybe Google Translate will help. It confirms that the cross flow exchanger's efficiency is 60%-70%, and adds that using 2 of them can be 95% efficient. Also, there is a spiral heat exchanger, which appears to be just aluminum foil rolled up into a spiral tube. The benefits are 85% efficiency and frost resistance (frost is the main enemy of cross- and counter-flow cells, requiring heating elements to keep the airflow from getting restricted).

[1blueox]

These are fascinating posts. Somebody asked about plans for 180 degree counter-flow exchangers so I thought I'd post.

I'm making a counter-flow air to air exchanger out of plywood and aluminum foil as an experiment. The design is very simple: imagine a piece of plywood as wide as the foil and as long as you want. Along the long edges are 1x2's to support the foil. Then the foil is laid on them. On top of the foil at its edges are another pair of 1x2's, with another sheet of plywood on top. Imagine folding the whole thing back on itself every couple of feet giving you two channels for the air, separated by foil (obviously you can't fold the plywood, that's just to give the concept). Add two small fans to move the air, some duct work at each end, and there you have it!

Those of you with far more experience than I have can improve on materials and dimensions, but if the foil is 18 inches wide and maybe 30 feet long, it should do a pretty good job. Humidity is not much of a factor where I live, but if condensation becomes a problem I'll clearly have to modify things a bit. This version is just for my own fun.

[AC_Hacker]

1bluebox,

Originally Posted by 1blueox

I'm making a counter-flow air to air exchanger out of plywood and aluminum foil as an experiment...

This sounds like a worthy project.

From my Internet research, it learned that there are two types of air energy recovery schemes. One uses non-porous membrane material, like aluminum foil, and the other uses a porous material that will allow condensing water to re-humidify incoming air. This might suggest other materials for you to try.

Also, it would seem to me that you'd want to go much thinner than 1x2 for your membrane separator. I'd think that membrane spacing on the order of 1/8 inch would be more in the ball park.

I also came across a DIY ERV discussion wherein someone was considering using a material like plastic food wrap for the membrane material. Seems like such a material would be cheap, easy to work with, quiet, and unaffected by condensation.

As my home insulation and infiltration project progresses, I'm beginning to notice that the controlled admission of new air is now required keep the comfort level at an acceptable level.

Regards,

-AC_Hacker

[Piwoslaw]

Originally Posted by AC_Hacker

If we can discover the source of the cells, we can build the box ourselves.

I found a (Swedish?) company that is a global supplier of heat exchangers:
Heatex AB

No idea of prices, but 'm sure that if we group-ordered a few hundred, then we could probably negotiate a deal

[AC_Hacker]

Originally Posted by Piwoslaw

I found a (Swedish?) company that is a global supplier of heat exchangers:
Heatex AB

Piwoslaw,

Don't know if you saw it, but the company has some interesting ERV design software (more properly, sizing software). So if one were going to try to fabricate their own Energy Recovery Ventilator, You could get a good idea where to begin.

The link is here:

Heatex AB - The No.1 Air-to-Air Heat Exchanger Company: Thanks!

... If this doesn't work for you,maybe go to the root URL and look for "software".

Regards,

-AC_Hacker