The exchanger consists of an artery making direct contact alongside another artery. .
The temperature gradient along the exchanger is great at the start of the length of the exchanger but minimal or nonexistent at the end of the length of the exchanger.
Warm blood flowing out from the core of the body moves in the same direction as the cool blood flowing alongside it from an extremity.
The temperature differential between warm and cold blood is small at any point along the two "pipes" carrying the blood.