Abstract: An apparatus and method for cooling hot fluids, especially exhaust gases, with a multi-pass cooler core. The cooler core is particularly useful for cooling exhaust gases flowing in an exhaust gas recirculation (EGR) system or regime in operative association with an internal combustion engine, such as a diesel engine. Cooled gases are recirculated to the engine input to help reduce noxious exhaust emissions. The invention utilizes unequal areas-in-flow between the first exhaust pass through the core and the second and subsequent passes through the core. The first pass through the core features an area-in-flow comparatively larger than the area-in-flow of the second pass. The difference in areas-in-flow between passes influences gas velocities to reduce fouling, despite changes in exhaust gas temperature between passes through the core.

Abstract: Heat exchangers, constructed in accordance with principles of this invention, comprise a plurality of first passages, for transporting a first fluid or gas therethrough, and one or more second passages for transporting a second fluid or gas therethrough. The second passages are positioned adjacent to the first passages to permit a desired transfer of thermal energy from the first passages to the second passages. At least one manifold is placed in communication with one of the first or second passages. The manifold includes an opening disposed therethrough for receiving or dispensing the first or second fluid or gas to or from the first or second passages. The heat exchanger includes a flow director disposed therein for diverting or distributing the flow of first or second fluid or gas in a manner different from a natural fluid or gas flow within the heat exchanger.