Charge Air Humidification of Fuel Cells

Abstract

A fuel cell system includes a fuel cell stack that receives a cathode feed gas and has an exhaust stream and a heat transfer stream flowing therefrom. A charge-air heat exchanger enables heat transfer between the heat transfer stream and the cathode feed gas. The charge-air heat exchanger also enables heat transfer between the heat transfer stream and the cathode feed gas to compensate for the adiabatic cooling effect. Furthermore, the charge-air heat exchanger vaporizes the liquid water to provide water vapor. The water vapor humidifies the cathode feed gas.

1 - 9 . (canceled) 
     
     
         10 . A fuel cell system, comprising:
 a fuel cell stack that exhausts an exhaust stream;   a heat transfer system that supplies a heat transfer fluid through said fuel cell stack; and   a multi-stage charge-air heat exchanger having first stage and second stages and that enables heat transfer between said heat transfer fluid and a cathode feed gas and that enables heat transfer between said heat transfer fluid, said cathode feed gas and liquid water to vaporize said liquid water providing water vapor, wherein said water vapor humidifies said cathode feed gas.   
     
     
         11 . The fuel cell system of  claim 10  further comprising a first stage injector that injects a portion of said liquid water into said cathode feed gas within said first stage. 
     
     
         12 . The fuel cell system of  claim 10  further comprising a second stage injector that injects a portion of said liquid water into said cathode feed gas within said second stage. 
     
     
         13 . The fuel cell system of  claim 10  further comprising a condenser that condenses water vapor in said exhaust stream to provide said liquid water as a condensate. 
     
     
         14 . The fuel cell system of  claim 10  further comprising a compressor that compresses said cathode feed gas. 
     
     
         15 . The fuel cell system of  claim 14  wherein said compressor is upstream of said charge-air heat exchanger and receives a portion of said liquid water to humidify said cathode feed gas within said compressor. 
     
     
         16 . The fuel cell system of  claim 15  further comprising an injector arranged to inject said liquid water into said cathode feed gas within said compressor. 
     
     
         17 . The fuel cell system of  claim 15  wherein said liquid water is vaporized within said compressor during a compression process. 
     
     
         18 . The fuel cell system of  claim 10  wherein a portion of said liquid water is injected into said fuel cell stack to humidify said cathode feed gas within said fuel cell stack. 
     
     
         19 . A method of humidifying a cathode feed gas supplied to a fuel cell stack, comprising:
 flowing said cathode feed gas through a charge-air heat exchanger;   injecting liquid water into said cathode feed gas within said charge-air heat exchanger; and   vaporizing said liquid water within said charge-air heat exchanger via heat transfer from a heat transfer fluid to humidify said cathode feed gas.   
     
     
         20 . The method of  claim 19  further comprising condensing water vapor within an exhaust stream of said fuel cell stack to form said liquid water. 
     
     
         21 . The method of  claim 19  further comprising compressing said cathode feed gas within a compressor prior to said step of flowing said cathode feed gas through said charge-air heat exchanger. 
     
     
         22 . The method of  claim 21  further comprising injecting a portion of said liquid water into said compressor to humidify said cathode feed gas during a compression process. 
     
     
         23 . The method of  claim 19  further comprising injecting a portion of said liquid water into said fuel cell stack to humidify said cathode feed gas within said fuel cell stack.