Patent ID: 6880628

Claim:
A heat exchanger for use in a fuel cell system, the heat exchanger comprising: heat transfer tube elements having a flat passage allowing flow of a cooling medium therein; outer fins retained adjacent the heat transfer tube elements allowing flow of a gas there through; and a core formed by laminating the heat transfer tube elements and the outer fins in order; wherein the gas flows through the outer fins in a direction orthogonal to the direction of cooling medium flow which flows in the passage in each heat transfer tube element; and a passage in at least a section of the passage for cooling medium provided in each heat transfer tube element comprising a large passage and a small passage group disposed in parallel, the large passage having a large width and being provided upstream to the core with respect to the direction of gas flow, and the small passage group comprising a plurality of small passages being narrower than the large passage and being provided downstream of the core with respect to the direction of gas flow; wherein the small passage group has a width corresponding to 20-40% of a total width of the cooling medium passage.