The heat exchanger system includes a first heat exchanger assembly including a plurality of airfoil members circumferentially spaced in a flow stream of an annular duct. Each airfoil member including a radially inner end and a radially outer end and a first internal flowpath configured to channel a flow of cooled fluid therethrough. The heat exchanger assembly includes a second heat exchanger assembly including a plurality of fin members extending proximate the flow stream and a second internal flowpath configured to channel a flow of cooled fluid therethrough. The heat exchanger assembly includes a header system including a conduit path configured to couple the first heat exchanger assembly and the second heat exchanger assembly in flow communication. The header system includes an inlet connection configured to receive a flow of hot fluid from thermal loads and an outlet connection configured to direct cooled fluid to thermal loads.
