This is called a counter-flow heat exchanger or countercurrent exchange, it's very commonly used in industrial applications, for both gas or fluid flow. This s

This is called a counter-flow heat exchanger or countercurrent exchange, it's very commonly used in industrial applications, for both gas or fluid flow. This setup is very efficient at heat transfer, and can counter-intuitively produce a higher output temperature than the counterflow's input temperature. https://en.wikipedia.org/wiki/Countercurrent_exchange https://en.wikipedia.org/wiki/Countercurrent_exchange