The Geometry of Heat Transfer

In crossflow the streams cross at right angles; in counterflow they run opposite. The difference decides how much energy is recovered.

Temperature Profiles

Counterflow lets the cold outgoing air meet the coldest part of the incoming stream along the whole length, so the average gradient stays high. Crossflow has a varying gradient and a warmer cold-exit region that wastes potential.

The Numbers

At equal size and flow, counterflow typically reaches 70 to 75 percent sensible effectiveness versus 60 to 65 percent for crossflow.

Trade-off

Counterflow cores are harder to build and seal, so crossflow is common where cost and simplicity win. Choose counterflow when effectiveness is the priority.