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Old 03-04-10, 12:31 AM   #13
Piwoslaw
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Quote:
Originally Posted by Xringer View Post
Those things do look large. But, it seems logical that a smaller unit would work for smaller houses, if you used a slower air-flow.
Since slower air will get more of a chance to give up it's heat before leaving the unit.
I believe it was in that MAKE article which AC_Hacker linked (I can't get it to open this morning) it was said that the lowest speed setting for the fans was not the most efficient, that it seemed to exchange more heat with a higher speed. Maybe with more air coming through there is a larger DeltaT, increasing the amount of heat absorbed?

I've noticed that the main two issues when constructing recuperators are
  1. Cross-section, which limits the amount of air that can be pushed through the unit,
  2. Surface area, which limits the amount of heat that can be transfered from one airflow to the other.
If the unit is very small, then either the surface area is puny, or it can't handle a large volume of air (pumping losses), or both. The big DIY counter-current unit in one of the pictures I posted previously had its largest dimension probably around 150cm, the other two below 100cm, and its exchange surface area is about 25m2.
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