Passive Housing

[Martin Bonner]

I can't provide a counter example for /heat/ exchangers, but your lungs are a non-counter current gas exchanger. (Birds on the other hand use a more efficient and more complex counter current system.)

[Alan Braggins]

I can:

the "why" is "because the crossflow is cheaper than counterflow".)

[Doctor Drivel]

The most common is the plate heat exchanger inside combis. Plate heat exchangers on some combis are designed not to be so efficient as to drop the return water so much the boiler cannot raise the temperature on the primary flow side enough. This also may affect the delta T of the main heat exchanger and have adverse effects, such as cracking. Long thin high kW plate heat exchangers extract an amazing amount of heat from incoming water and are used on heat banks.