Patent ID: 6920916

Claim:
A layered heat exchanger comprising: generally rectangular metal plates each having formed in one surface thereof front and rear fluid channel forming recessed portions divided by a vertically elongated partition ridge, front and rear upper tank forming recessed portions continuous with upper ends of these portions and having a larger depth than these portions, and front and rear lower tank forming recessed portions continuous with lower ends of these portions and having a larger depth than these portions, the front and rear upper tank forming recessed portions having respective fluid passage apertures formed in their bottom wall, the front and rear lower tank forming recessed portions having respective fluid passage apertures formed in their bottom wall, each pair of adjacent metal plates being fitted together in superposed layers with their recessed surfaces opposed to each other to join opposed partition ridges of the metal plates to each other, to join opposed peripheral edges thereof to each other and to thereby form a flat tube portion having front and rear flat channels and front and rear upper tank portions and front and rear lower tank portions which are continuous with the channels, a multiplicity of flat tube portions being arranged in parallel to cause the front upper tank portions of the adjacent parallel flat tube portions to communicate with each other, the rear upper tank portions thereof to communicate with each other, the front lower tank portions thereof to communicate with each other, and the rear lower tank portions thereof to communicate with each other, wherein the metal plate is provided at one of an upper end and a lower end of the partition ridge with a fluid flow direction changing passage forming caved portion having a bottom wall of circular-arc cross section, the front and rear upper tank portions of the flat tube portion or the front and rear lower tank portions thereof being held in communication with each other through a fluid flow direction changing passage having an approximately circular cross section and formed by the caved portions which are opposed to each other, and wherein the opposed caved portions comprise circular-arc portions corresponding respectively to angles of at least 60 degrees to less than 90 degrees each, above and below a center line of the opposed caved portions and circular arc in cross section to have a same radius of curvature.