Multi-pass exhaust gas recirculation cooler

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.

1 - 8 . (canceled)  
   
   
       9 . A multi-pass heat exchanger core comprising: 
 at least one coolant plenum for containing flowing coolant;    at least one first-pass plenum for containing a flowing heated gas, said first-pass plenum adjacent to said at least one coolant plenum, and said first-pass plenum defining a first area-in-flow of the heated gas; and    at least one subsequent-pass plenum for containing the heated gas, said subsequent-pass plenum adjacent to said at least one coolant plenum, and said subsequent-pass plenum defining a second area-in-flow of the heated gas;    wherein the ratio of said first area-in-flow to said second area-in-flow is between about 1.3 to 1 and about 1.7 to 1, and the heated gas flows past a coolant plenum at least twice.    
   
   
       10 . An apparatus according to  claim 9 , further comprising: 
 a plurality of coolant plenums;    a plurality of first-pass plenums, said plurality of first-pass plenums defining a first plurality of exhaust passages to direct gas flow through said first-pass plenums; and    a plurality of subsequent-pass plenums, said plurality of subsequent-pass plenums defining a second plurality of exhaust passages to direct gas flow through said subsequent-pass plenums;    wherein said first plurality of exhaust passages substantially exceed in number said second plurality of exhaust passages, and said first-pass plenums and said subsequent- pass plenums are disposed in an alternate manner between cooling plenums, every second plenum being a cooling plenum.    
   
   
       11 . An apparatus according to  claim 9  wherein: 
 said plenums are substantially parallel; and    said first-pass plenums are separated from said subsequent-pass plenums by at least one elongate divider substantially perpendicular to said plenums.    
   
   
       12 . A multi-pass folded-flow exhaust gas recirculation cooler comprising: 
 a plurality of coolant plenums for containing flowing coolant;    a plurality of first-pass plenums, defining a first-area-in-flow, for containing hot exhaust oases, said first-pass plenums disposed adjacent to at least one of said coolant plenums; and    a plurality of subsequent-pass plenums, defining a second area-in-flow for containing the hot exhaust gases, said subsequent-pass plenums disposed adjacent to at least one of said coolant plenums;    wherein the total number of said first-pass plenums substantially exceeds the total number of said subsequent-pass plenums, whereby a ratio of the first area-in-flow to the second area-in-flow is between about 1.3 to 1 and about 1.7 to 1.    
   
   
       13 . The apparatus of  claim 12  further comprising: 
 a plurality of exhaust passages in each of said first-pass plenums; and    a plurality of exhaust gas passages in each of said subsequent-pass plenums.    
   
   
       14 . A multi-pass cross-flow heat exchanger core comprising: 
 a plurality of coolant plenums for containing flowing coolant;    a plurality of first-pass plenums for containing a flowing heated fluid and defining a first area-in-flow of the heated fluid, said first-pass plenums installed adjacent to said coolant plenums;    a plurality of subsequent-pass plenums for containing the heated fluid and defining a second area-in-flow of the heated fluid, said subsequent-pass plenums disposed adjacent to said coolant plenums; and    at least one elongate divider substantially perpendicular to said plenums and separating said first-pass plenums from said subsequent-pass plenums;    wherein said plenums are substantially parallel, the contained heated fluid flows past a coolant plenum at least twice, and a ratio of a first area-in-flow to a subsequent area-in-flow is between about 1.3 to 1 and about 1.7 to 1.