Abstract: The invention relates to a recuperator having an improved core within the primary heat transfer surface. This core, by its unique construction, achieves a combination of reradiative and convective heat transfer which outperforms either of these separate modes while maintaining a low pressure loss. The core consists of a series of radial plates between which are a series of triangular baffles arranged at an angle with the horizontal of 45.degree. to 70.degree.. The baffles intercept the flow of flue gas and gently channel the flow of gas into a swirling pattern, thereby enhancing convective heat transfer while maintaining low pressure loss. The staggered triangular baffles also tend to reflect radiation that would otherwise be lost back to the primary heat transfer surface.

Abstract: Apparatus and method for carburizing and carbonitriding ferrous metal work in a continuous furnace having aligned heating, carburizing and diffusing zones. Each zone is provided with fan means in at least one side wall of the furnace, with both the inlet and the outlet of the fan at a level below the work trays which are conveyed through the furnace so that the gas atmosphere is pulled downwardly through the work at one or more pier positions within a processing zone and pushed upwardly through the work at the remaining pier positions within the zone. By proper refractory design and fan locations a more uniform and controllable flow pattern is provided throughout the length and width of each processing zone.