View Single Post
Old 03-01-10, 02:30 PM   #10
Super Moderator
Piwoslaw's Avatar
Join Date: May 2009
Location: Warsaw, Poland
Posts: 920
Thanks: 173
Thanked 93 Times in 77 Posts

Originally Posted by AC_Hacker View Post
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).

Last edited by Piwoslaw; 03-01-10 at 03:09 PM..
Piwoslaw is offline   Reply With Quote
The Following User Says Thank You to Piwoslaw For This Useful Post:
Hv23t (12-11-12)