Heat exchanger

Abstract

A heat exchanger ( 50 ) is provided for transferring heat between first and second fluids ( 52 ) and ( 54 ) having a maximum operating mass flow rate through the heat exchanger ( 50 ) and mass flow rates that are substantially proportional to each other. The heat exchanger ( 50 ) provides essentially constant outlet temperatures for the first and second fluids ( 52,54 ) for all of the flow rates within the operating spectrum of the heat exchanger ( 50 ) without the use of an active control system. The heat exchanger ( 50 ) is of particular use in the fuel processing system ( 36 ) of proton exchange membrane type fuel cell systems.

1 - 12 . (canceled)  
   
   
       13 . A fuel processing system for a proton exchange membrane type fuel cell system, the fuel processing system comprising: 
 an auto-thermal reformer having an inlet connected to the system to receive a humidified air/fuel mixture therefrom and an outlet connected to the system to supply a reformate flow thereto;    a water-gas shift reactor having an inlet connected to the system downstream from the auto-thermal reformer to receive the reformate flow therefrom and an outlet connected to the system to supply a reformate flow with a reduced carbon monoxide content thereto;    a recuperative heat exchanger including first and second flow paths,    the first flow path connected to the system upstream of the auto-thermal reformer to preheat the humidified air/fuel mixture to a desired inlet temperature range for the auto-thermal reformer,    the second flow path connected to the system downstream of the auto-thermal reformer and upstream of the water-gas shift reactor to cool the reformate flow to a desired inlet temperature range for the water-gas shift reactor,    the first and second flow paths arranged relative to each other to supply the desired inlet temperature ranges for the auto-thermal reformer and the water-gas shift reactor at all flow rates within the anticipated operating spectrum of the fuel cell system without the use of an active control system.    
   
   
       14 . The fuel processing system of  claim 13  wherein the recuperative heat exchanger and the auto-thermal reformer are an integrated unit.  
   
   
       15 . A method of operating a fuel processing system for a proton exchange membrane type fuel cell system, the method comprising the steps of: 
 a) flowing an air/fuel mixture through a first flow path of a recuperative heat exchanger to an auto-thermal reformer located downstream of the first flow path;    b) flowing a reformate from the auto-thermal reformer through a second flow path of the recuperative heat exchanger located downstream of the auto-thermal reformer and upstream of a water-gas shift reactor;    c) providing the air/fuel mixture from the first flow path to the auto-thermal reformer within a desired catalytic temperature range for all flow rates within the operating spectrum of the fuel cell;    d) providing the reformate from the second flow path to the water-gas shift reactor within a desired catalytic temperature range for all flow rates within the operating spectrum of the fuel cell; and    e) performing steps c) and d) without an active control of the recuperative heat exchanger.    
   
   
       16 . An integrated unit for a fuel processing system of a fuel cell system, the integrated unit comprising: 
 a recuperative heat exchanger including a first flow path for an air/fuel mixture and a second flow path for a reformate, each flow path having an entrance and a exit; and    an auto-thermal reformer, the auto-thermal reformer including; 
 an inlet connected to the exit of the first flow path to receive the air/fuel mixture therefrom; and  
 an outlet connected to the entrance of the second flow path to direct the reformate thereto.  
   
   
   
       17 . The integrated unit of  claim 16  wherein each of the first and second flow paths are multi-pass flow paths, and at least part of the auto-thermal reformer is surrounded by a final pass of the first flow path and an initial pass of the second flow path.  
   
   
       18 . The integrated unit of  claim 16  wherein at least part of the auto-thermal reformer is surrounded by a portion of the recuperative heat exchanger.  
   
   
       19 - 20 . (canceled)