Patent ID: 8276652

Claim:
A flat tube heat exchanger comprising: at least one header; a plurality of spaced apart tubes in fluid communication with said header; and a plurality of fins disposed between said tubes, said fins further comprising: a base wall having at least one longitudinal axis, a first end, a second end, and a middle portion; at least one turnaround rib disposed in the middle portion of the base wall; a plurality of spaced apart entrance louvers disposed between the first end of the base wall and the turnaround rib, the entrance louvers having a first edge and a second edge, the first edge disposed on a first side of the longitudinal axis and the second edge disposed on a second side of the longitudinal axis, a width of each of the entrance louvers defined as a distance between the first edge of each of the entrance louvers and the second edge of each of the entrance louvers, wherein the width of the entrance louvers increases moving from the first end of the base wall to the middle portion of the base wall, wherein each of the entrance louvers is disposed at a predetermined angle α in respect of the longitudinal axis of the base wall, the predetermined angle α decreasing for the entrance louvers moving from the first end of the base wall to the turnaround rib; and a plurality of spaced apart exit louvers disposed between the turnaround rib and the second end of the base wall, the exit louvers having a first edge and a second edge, the first edge disposed on a first side of the longitudinal axis and the second edge disposed on a second side of the longitudinal axis, a width of each of the exit louvers defined as a distance between the first edge of each of the exit louvers and the second edge of each of the exit louvers, wherein the width of the exit louvers decreases moving from the middle portion of the base wall to the second end of the base wall, wherein each of the exit louvers is disposed at a predetermined angle β in respect of the longitudinal axis of the base wall, the predetermined angle β decreasing for the exit louvers moving from the turnaround rib to the second end of the base wall, wherein at least one of the entrance louvers and the exit louvers has a shape in cross section configured to affect at least one of an airflow and a pressure drop through the entrance louvers and the exit louvers.