Abstract: A turbine engine is provided with a primary surface, counterflow heat exchanger for preheating the compressed air from the compressor prior to its entry into the combustor. The recuperator includes three concentric cylindrical shells which completely encircle the hottest components of the engine. The outermost shell includes a plurality of inlet openings for receiving air from the compressor, and a plurality of outlet openings for discharging the air into the combustor. The innermost shell includes a plurality of inlet openings for receiving gases from the turbine and a plurality of outlet openings communicating with an exhaust duct. The central shell is a corrugated tube which divides the space between the inner and outer shells into a plurality of concentric annular flow chambers, and allows heat transfer between adjacent chambers Annular turbulators may be inserted in the chambers.