Reversing air flow across a cathode for a fuel cell

Abstract

A fuel cell assembly having means for providing tempered air to, and removing spent air from, air-flow passages across the cathode. The air flow path includes means for reversing the direction of flow across the cathode periodically to reverse the roles of the leading and trailing edges of the cathode to prevent temperature differences across the cathode from exceeding 200° C., and thus to prevent damage to the cathode from thermally-induced stresses during startup heating and steady-state cooling.

1 . A reversing-flow air tempering and supply system for supplying air from a source through air-flow passages of a fuel cell having first and second ports connected to the air-flow passages, comprising: 
 a) means for receiving air from said source and tempering said air to a predetermined temperature; and    b) flow-selection means for receiving tempered air from said tempering means and being connected across said first and second ports and being reversibly acting at a predetermined periodicity to direct said tempered air sequentially in periodically alternating directions through said air-flow passages between said first and second ports;    c) wherein said air-flow passages are at a first temperature and wherein a temperature difference (ΔT) is defined between said first temperature and said predetermined temperature.    
     
     
         2 . (canceled)  
     
     
         3 . A system in accordance with  claim 1  wherein the frequency of said reversing is about 2 Hz.  
     
     
         4 . (canceled)  
     
     
         5 . A system in accordance with  claim 1  wherein said predetermined temperature is higher than said first temperature, said system being in a heating mode with respect to said air-flow passages.  
     
     
         6 . A system in accordance with  claim 1  wherein said predetermined temperature is lower than said first temperature, said system being in a cooling mode with respect to said air-flow passages.  
     
     
         7 . A system in accordance with  claim 1  wherein said ΔT is greater than 200° C.