A design that is different from the cross-flow types.
Klingenburg GmbH - Energy Recovery - Counterflow plate heat exchanger
Appears to be very similar to the core used in the Westaflex mentioned earlier.
Don't overlook
this link, it has lots of interesting literature.
Here's a grab from one of the the documents above.
The company appears to be in the business of selling high efficiency counterflow cores.
Regards,
-Jim