Abstract: A heat recuperator and a method for recuperating heat from a furnace having a nozzle-mix burner to enhance the efficiency of combustion of one or more burners associated with the furnace. The recuperator comprises an exhaust tube which is connectable to a furnace combustion chamber for receiving heated exhaust gas therethrough. The exhaust tube has an outer cylindrical wall and an inner metallic tube concentrically supported therein. An annular space is defined between the outer cylindrical wall and the inner tube. The inner tube is formed, in at least a major length thereof, with a plurality of corrugations. An air inlet connection is provided at an inlet end of the annular space downstream of the exhaust tube. The annular space also has an outlet upstream of the exhaust tube adjacent an inlet end thereof and connectable to a burner supplying same with heated combustion air.