Two-stage heat exchanger

Abstract From the Canadian patent

Improved furnaces axe described in which secondary and tertiary heat exchanges are incorporated into new and existing hot-air furnace systems for controlled cooling of hot combustion products by co-current and countercurrent heat exchanges. Hot combustion products are cooled to a temperature at which latent heat of water vapour contained in combustion gases are substantially recovered. In one embodiment of our invention a secondary, heat exchanger comprises inter alia a closed hollow annular drum concentric with and spaced from a cylindrical combustion chamber, said annular drum having an upper annulus preferably filled with randomly packed refractory material. A second embodiment of our …