A gas turbine engine includes a shaft comprising a first compressor, a fan assembly, and a power circuit that provides power to the shaft in a closed-loop system. An inner housing houses at least a portion of the shaft, the first compressor for compressing a core stream of air, and a combustor. A baffle encloses a portion of the inner housing and forms a first air passageway therebetween. A nacelle encloses a portion of the baffle and forms a second air passageway therebetween. A heat exchanger is positioned in the second air passageway that rejects heat from the power circuit into a heat rejection stream of air passing through the second air passageway. Air is accelerated as streams in parallel and via the fan assembly as the core stream into the inner housing, as a bypass flow stream of air through the first volume, and as the heat rejection stream.