Patent ID: 7870671

Claim:
A method of manufacturing a plate heat exchanger comprising providing a plurality of stacked plates which limit heat exchange of two or more separate fluids across said plates, said plates each including a double wall configuration to prevent one or more of said two or more fluids from leaking through a wall of the plates and entering a path of an other of said one or more of said two or more fluids; sealingly interconnecting the double walls of each of said plates around borders of port holes in the plates; providing to each plate of the stacked plates, prior to being brazed, brazing material on a surface thereof which engages a surface of another plate of said stacked plates; and configuring areas of mutually contacting wall surfaces of two of said plates forming a double wall plate around borders of a port hole to only partly cover each other; wherein the borders of the port holes in walls engaging each other in a plate have equal diameters and are provided with relatively displaced indentations.