I'm working out the details of the design now.
From reading product literature, it looks like condensation will be an issue. There seem to be various schemes involving sensors and circuitry and "drying cycles", but for now I'm going to plunge ahead and ignore condensation to see just how big a problem it really is.
Since my realization that I have greatly over-sized my core, I have decided to go with a dual-core design. I'll divide the core stack in two, the cores being in series, with the air passing from one core to the next. This will double the distance over which heat exchange will take place, and should approximate a counter-flow heat exchanger.
So the next design issue will be duct sizing... I recall that Piwoslaw posted this:
Quote:
Originally Posted by Piwoslaw
As for air flow, I believe the minimum is 0.5 house volumes per hour, the maximum is either 2 or 4 house volumes per hour (don't remember). When replacing more than 2 (or 4) house volumes per hour the heating/cooling/recovery system may not be able to keep up, leading to noticeable drafts and energy loss. Also, the ducts should be sized to keep air speed below 5 m/s to keep noise down.
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There is a wonderful little program called
CurveExpert, that is true shareware and does a great job of curve fitting and formula generation.
I tried inputting
value tables from HVAC sites, in order to generate an automated formula for you, my reader. Unfortunately my first attempt failed so I found some online calculating pages that will calculate duct sizes from CFM.
Here one for metric
Here's one for US measurements
And here is a table just to double check your results.
The issue here is that if the air in the duct flows too quickly, it goes into turbulent mode and can make a lot of noise. A friend of mine re-did the ductwork in his house and neglected this issue. Silence really is golden.
The ventilation rate I previously calculated was about 15CFM, at least that's what I rounded it up to.
Using the
online calculator for US measurements, and using the value of 15 CFM, and using PVC as my duct material, I get a diameter of 2.85 inch ID.
So anything bigger than 2.85 inch will be nice and quiet. Three inch looks to be a winner so long as I keep my runs short. Four inches will just cost me more money and it will require more insulation to be efficient.
Bigger isn't always better.
Regards,
-AC_Hacker
PS: Next is fans
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