A method and a system for a heat exchanger assembly are provided. The heat exchanger assembly includes one or more arcuate heat exchanger segments each including an inlet header configured to extend circumferentially about a circumference of an inner surface of a fluid flow duct, and an outlet header configured to extend circumferentially about the fluid flow duct. The heat exchanger assembly also includes a first serpentine heat exchanger tube extending between the inlet header and the outlet header and including a series of flow path segments having a gradually changing direction defined by a bend radius of the tube such that a direction of flow through the serpentine heat exchanger tube reverses between the inlet and the outlet headers and a second serpentine heat exchanger tube extending between the inlet header and the outlet header, the second serpentine heat exchanger tube co-planar with the first serpentine heat exchanger tube.