Countercurrent exchange to the extreme. It even uses countercurrent exchange of methanol as a deicer; it sprays in pure methanol at the coldest parts of the he

Countercurrent exchange to the extreme. It even uses countercurrent exchange of methanol as a deicer; it sprays in pure methanol at the coldest parts of the heat exchanger, captures it somehow, and sprays the increasingly waterlogged mixture farther and farther upstream where it's warmer and doesn't need to be as concentrated to prevent freezing.