Multi-pass exhaust gas recirculation cooler

A multi-pass exhaust gas recirculation cooler comprising:

• a plurality of coolant plenums for containing flowing coolant;
• a plurality of first-pass plenums for containing hot exhaust gases, each of said first-pass plenums disposed adjacent to at least one of said coolant plenums;
• a plurality of subsequent-pass plenums for containing the hot exhaust gases, each of said subsequent-pass plenums disposed adjacent to at least one of said coolant plenums;
• a plurality of exhaust passages defined in each of said first-pass plenums;
• and
• a plurality of exhaust gas passages defined in each said subsequent-pass plenums;
• wherein said exhaust gas passages have substantially equal radial cross sectional areas, and wherein further the total number of exhaust passages in said plurality of first-pass plenums substantially exceeds the total number of exhaust passages in said plurality of subsequent-pass plenums, and the exhaust gases flow past a coolant plenum at least twice.

A method for cooling recirculated exhaust, the method comprising:

• conveying coolant through at least one coolant plenum;
• directing heated exhaust through at least one first-pass plenum disposed adjacent to the at least one coolant plenum, defining a first area-in-flow within the first-pass plenum;
• re-directing the heated exhaust through at least one subsequent-pass plenum disposed adjacent to the at least one coolant plenum;
• defining a second area-in-flow within the subsequent-pass plenum, the first area-in-flow substantially exceeding the second area-in-flow;
• and
• permitting heat energy to be removed from the exhaust by coolant convection.