side in the flow direction of the cooling medium.
Further, another heat exchanger of the present invention is characterized in that a bulged portion protruding on the cooling medium flow path side is formed in the cooling medium flow portion by denting at least any one of the two flat plates from the outside, a plurality of elliptical or oval cylindrical portions whose major diameter is oriented in the flow direction of the cooling medium are provided between two flat plates by butting the top portion of the bulged portion to the opposite flat plate, and this plurality of cylindrical portions is formed of shapes gradually decreasing in size as the cooling medium flows toward the downstream side in the flow direction of the cooling medium.
In this case, itthe opening portion.
Further, another heat exchanger of the present invention is characterized in that a flow path cross-section of the cooling medium flow path communicating with the space on the inlet side (inlet side space) of the cooling medium is gradually reduced as the cooling flows toward the downstream side in the flow direction of the cooling medium.
Further, another heat exchanger of the present invention is characterized in that a flow path cross-section of the cooling medium flow path communicating with the space on the outlet side (outlet side space) of the cooling medium is gradually magnified as the cooling medium flows toward the downstream side in the flow direction of the cooling medium.
Further, the present invention is characterized in that in a heat exchanger wherein a cooling