Joseph Meehan wrote:

What exactly is a contra-flow heat exchanger? How is it powered? If
it is not powered, how does it violate a basic law of physics?

"Wayne Whitney" wrote in message
...

On 2007-11-23, Joseph Meehan wrote:

If you start with 80º interior and 60º exterior the best you can do is
to get 70º air coming into the home and 70º air exiting the home.


In a contra-flow heat exchanger, I believe you can get 100% heat
exchange, i.e. the air exiting the house is 60 degrees and the air
entering the house is 80 degrees.



What law of physics did you have in mind, top poster?

Maybe you should read up on heat exchangers:

http://en.wikipedia.org/wiki/Heat_exchanger

http://en.wikipedia.org/wiki/Countercurrent_exchange