Multi-pass heat exchanger

Abstract

A multi-pass heat exchanger is provided. The multi-pass heat exchanger may be used in a fuel processing subsystem for cooling a reformate flow or in any other application where uniform outlet temperatures are desired. The multi-pass heat exchanger includes a plurality of tube run groups having a first pass, an intermediate pass and a final pass. The respective locations of the passes relative to each other provide more uniform outlet temperatures than conventional automotive-style, parallel flow, single-pass heat exchangers.

1 . A heat exchanger for transferring heat between a first fluid flow and a second fluid flow, the heat exchanger comprising: 
 an inlet manifold;    an outlet manifold;    a plurality of aligned and spaced tube run groups extending between the inlet manifold and the outlet manifold to direct the first fluid flow through the heat exchanger, each tube run group having three parallel tube runs; 
 the tube runs of each tube run group including a first tube run coupled to the inlet manifold to direct the first fluid in a first direction, an intermediate tube run coupled to the first tube run to receive the first fluid therefrom and direct the first fluid in a second direction opposite the first direction, and a final tube run coupled to the intermediate tube run to receive the first fluid therefrom and direct the first fluid in the first direction to the outlet manifold, the intermediate tube run located adjacent the first tube run and the final tube run;  
   for each adjacent pair of tube run groups, the final tube run of one of the tube run groups of the pair being located adjacent the first tube run of the other tube run group of the pair; and    a plurality of fins extending between the adjacent tube runs of the tube groups to direct the second fluid flow between the adjacent tube runs of the tube groups from an inlet face to an outlet face of the heat exchanger.    
   
   
       2 . The heat exchanger of  claim 1  wherein each tube run group comprises a single tube that defines the three tube runs.  
   
   
       3 . The heat exchanger of  claim 2  wherein each single tube is arranged in a generally serpentine configuration.  
   
   
       4 . The heat exchanger of  claim 1  wherein the tube runs and fins have sufficient effectiveness under normal operating conditions to partially vaporize the first fluid flow where the first fluid flow enters the heat exchanger inlet manifold as a single-phase fluid and exits the heat exchanger outlet manifold as a two-phase fluid.  
   
   
       5 . The heat exchanger of  claim 1  wherein the tube runs are flattened tubes.  
   
   
       6 . The heat exchanger of  claim 1  wherein the fins are serpentine fins.  
   
   
       7 . The heat exchanger of  claim 1  wherein the tube runs are constructed of aluminum.  
   
   
       8 . A heat exchanger for transferring heat between a first fluid flow and a second fluid flow, the heat exchanger comprising: 
 an inlet manifold;    an outlet manifold;    a plurality of aligned and spaced tubes extending between the inlet manifold and the outlet manifold to direct the first fluid flow through the heat exchanger, each tube having three parallel tube runs; 
 the parallel tube runs of each tube including a first tube run coupled to the inlet manifold to direct the first fluid flow in a first direction, an intermediate tube run coupled to the first tube run to direct the first fluid flow in a second direction opposite the first direction, and a final tube run coupled to the intermediate tube run and the outlet manifold to direct the first fluid flow in the first direction, the intermediate tube run located adjacent the first tube run and the final tube run;  
   for each adjacent pair of tubes, the final tube run of one of the tubes of the pair being located adjacent the first tube run of the other tube of the pair; and    a plurality of fins extending between the adjacent tube runs of the tubes to direct the second fluid flow between the adjacent runs of the tubes from an inlet face to an outlet face of the heat exchanger.    
   
   
       9 . The heat exchanger of  claim 8  wherein the tube runs and fins have sufficient effectiveness under normal operating conditions to partially vaporize the first fluid flow where the first fluid flow enters the heat exchanger inlet manifold as a single-phase fluid and exits the heat exchanger outlet manifold as a two-phase fluid.  
   
   
       10 . The heat exchanger of  claim 8  wherein the tubes are flattened tubes.  
   
   
       11 . The heat exchanger of  claim 8  wherein the fins are serpentine fins.  
   
   
       12 . The heat exchanger of  claim 8  wherein the tubes are constructed of aluminum.  
   
   
       13 . The heat exchanger of  claim 8  wherein each of the tubes is arranged in a generally serpentine configuration.  
   
   
       14 . A method of transferring heat from a first fluid to a second fluid in a heat exchanger, the heat exchanger including a planar inlet face to receive the second fluid, a planar outlet face opposite the inlet face to exhaust the second fluid, a first fluid inlet on a first side of the faces, and a first fluid outlet on a second side of the faces opposite the first side, the method comprising the steps of: 
 flowing the first fluid from the inlet to the outlet via a plurality of aligned multi-pass flow paths;    each of the flow paths including a first pass extending between the first and second sides in a first flow direction transverse to the inlet and outlet faces, an intermediate pass extending between the first and second sides in a flow direction opposite the first direction transverse to the inlet and outlet faces, and a final pass extending between the first and second sides in the first flow direction, the passes being parallel to each other;    each of the intermediate passes running between the first and final passes of the associated flow path, for each adjacent pair of flow paths;    the final pass of one of the flow paths of the pair running adjacent the first pass of the other flow path of the pair;    flowing the second fluid from the first face to the second face via flow paths between and transverse to the passes; and    transferring heat between the first and second fluids as the first and second fluids flow through the respective flow paths.    
   
   
       15 . The method of  claim 14  wherein the first fluid comprises water.  
   
   
       16 . The method of  claim 14  further comprising the step of transferring sufficient heat to only partially vaporize the first fluid.