Patent ID: 7892690

Claim:
A method for controlling liquid delivery in a proton exchange membrane fuel cell system, the method comprising: moving a liquid at a flow rate using a pressure source, wherein the flow rate is between about 10 and about 200 milliliters per hour; flowing the liquid through a differential flow meter, wherein the differential flow meter is disposed after the pressure source in a flow path and before receipt of the liquid by a fuel processor included in the fuel cell system, the differential flow meter including a flow restriction and at least one sensor that is configured to measure differential pressure in the liquid before and after the liquid passes the flow restriction, wherein the flow restriction includes an orifice with a smaller opening than a line that supplies the liquid to the flow restriction; as the liquid flows past the flow restriction in the differential flow meter, using the at least one sensor of the differential flow meter to measure the differential pressure of the liquid before and after the liquid passes the flow restriction; determining flow rate of the liquid using the differential pressure; and changing the flow rate of the liquid.