Cooling devices with a circulating liquid coolant have been used to remove the heat generated in fuel cells in the fuel cell systems installed on movable objects such as electric automobiles.
For example, Japanese Patent Application Laid-open No. 2002-216817 disclosed such cooling device which decreases the liquid coolant bypass ratio to an electric conductivity reduction device (ion-exchange resin) when the temperature of the liquid coolant is high and electric conductivity is low, and increases the bypass ratio to the electric conductivity reduction device when the temperature of the liquid coolant is low and electric conductivity is high. With such technology, at a high temperature when high cooling performance is required, the bypass flow rate can be increased and priority can be placed on cooling, and at a low temperature when the amount of emitted heat is small, priority can be placed on reducing electric conductivity of liquid coolant.
Similar technology is also described in Japanese Patent Applications Laid-open No. 2003-123804 and 2003-123813.