Patent ID: 6938685

Claim:
A heat exchanger suitable for use as a coolant evaporator, comprising: a plurality of generally planar plates which are assembled to form a heat exchanger block or plate stack, wherein respective pairs of plates are joined together to enclose between them two discrete parallel ducts, which are delimited by the inside surfaces of the plates and by edge webs arranged on the longitudinal sides of paired plates and by a middle web arranged in the middle in the longitudinal direction of respective paired plates, the edge webs and middle webs projecting toward the inside of the plate pair and being brazed to one another in the inside and at the edge of the plates, said parallel ducts being capable of discrete streams of fluid flowing counter-currently in the respective ducts; said stack of plate pairs forming a plurality of said parallel ducts for flow of a first fluid in the longitudinal direction of the plates, and respective pairs being separated from one another to form a plurality of passageways for a second fluid to flow on the outside of the plates essentially transversely to the direction of flow of the first fluid; and each plate having elevations protruding out of the plane of the plate, which are formed by material deformation, and the plates comprising elevations directed into the inside of the plate pairs and also toward the outside of the plate pairs, with the elevations directed toward the outside of the plate pairs being configured as elongated portions, wherein the elongated portions are shaped in the form of beads, and the beads in a plate have different lengths.