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DoctorDoctor · 09-22-11, 06:32 PM

Yes, I was thinking of using fins to hold the center pipe. My point is to use K.I.S.S. (keep it simple stupid). Sure one can design and make a air to air heat exchanger with near perfect numbers - outside air is heated to almost that of inside air and vice versa, so that no heat energy is lost. Surface area is indeed the critical factor for heat exchange. The ideas like the "thermal wheel" look great but no one is going to build them. If you want better heat exchange, just make the exchanger longer. Not sure that the honeycomb is actually better than just adding another section of aluminum vent pipe to make it longer.

One would probably want an air flow so that the entire volume of air in the crawlspace (or basement) is pumped out at least once a day. If one increases airflow too much, one doesn't get as good heat exchange. Also, the humidified air in the outside part of the larger pipe will start freezing on the inner pipe (if the ambient temp is less than freezing).

One issue is that one doesn't want the fresh outside air that you have just pumped in to be pumped out. So the out-take can't be too close to the intake. I was think that a 90 degree corner on the outer tube with a hole cut out so the inner tube goes through it. One would seal all around this hole. I wish I could draw a picture.

09-22-11, 06:32 PM	#118
DoctorDoctor Lurking Renovator Join Date: Sep 2011 Location: Colorado Posts: 13 Thanks: 0 Thanked 1 Time in 1 Post	Really simple heat exchanger Yes, I was thinking of using fins to hold the center pipe. My point is to use K.I.S.S. (keep it simple stupid). Sure one can design and make a air to air heat exchanger with near perfect numbers - outside air is heated to almost that of inside air and vice versa, so that no heat energy is lost. Surface area is indeed the critical factor for heat exchange. The ideas like the "thermal wheel" look great but no one is going to build them. If you want better heat exchange, just make the exchanger longer. Not sure that the honeycomb is actually better than just adding another section of aluminum vent pipe to make it longer. One would probably want an air flow so that the entire volume of air in the crawlspace (or basement) is pumped out at least once a day. If one increases airflow too much, one doesn't get as good heat exchange. Also, the humidified air in the outside part of the larger pipe will start freezing on the inner pipe (if the ambient temp is less than freezing). One issue is that one doesn't want the fresh outside air that you have just pumped in to be pumped out. So the out-take can't be too close to the intake. I was think that a 90 degree corner on the outer tube with a hole cut out so the inner tube goes through it. One would seal all around this hole. I wish I could draw a picture.