Cooling system for a fuel cell stack

Abstract

A fuel cell cooling system is provided with a coolant pump for pumping fluid through coolant flow field passages in a fuel cell stack. A pressure control mechanism is provided for maintaining a pressure level within the fuel cell stack for causing a phase change of the coolant within the stack. Allowing the coolant to change phase to a gas inside the stack reduces the amount of coolant needed to cool the fuel cell stack and thereby reduces the energy needed to pump the coolant through the fuel cell stack.

1 . A cooling system, comprising: 
 a heat exchange member defining a coolant passage therein, said coolant passage having an inlet end and an outlet end;    a source of liquid coolant delivered to said inlet end of said coolant passage; and    a pressure control mechanism for controlling a pressure of said outlet end of said coolant passage at a predetermined pressure level to cause coolant in said coolant passage to boil at an operating temperature of the cooling system.    
     
     
         2 . The cooling system of  claim 1 , wherein said coolant passage includes a plurality of elongated passages.  
     
     
         3 . The cooling system of  claim 1 , further comprising a heat exchanger for cooling coolant received from said pressure control mechanism.  
     
     
         4 . The cooling system of  claim 1 , wherein said pressure control mechanism includes a pressure control valve.  
     
     
         5 . The cooling system of  claim 1 , wherein said source of liquid coolant includes a pump.  
     
     
         6 . The cooling system of  claim 1 , wherein said coolant passage progressively widens from an inlet end to an outlet end to accommodate liquid-to-gas expansion.