Plate heat exchanger

A plate heat exchanger for heat transfer between a first fluid and a second fluid, in which

• plate-formed heat transfer elements (1, 2) are permanently joined together in a plate package and said elements form between themselves, in alternating interspaces, first flow passages for said first fluid and second flow passages for said second fluid,
• each of said heat transfer elements (1, 2) comprises two plates (12, 13) abutting against each other and having through-openings (8a-11a) aligned with each other, and
• said through openings in the plates of the heat transfer elements form a first inlet channel and a first outlet channel through the plate package, which channels communicate with said first flow passages and are closed from connection with said second flow passages, and a second inlet channel and a second outlet channel through the plate package, which channels communicate with said second flow passages and are closed from connection with said first flow passages, wherein
• adjacent heat transfer elements (1, 2) are joined together in each of said interspaces (6) by means of three different and spaced permanent joints, a first joint of which surrounds an area covering the flow passage that is formed in the interspace (6) as well as the inlet channel (8) and the outlet channel (9) through the plate package, which channels communicate with the covered flow passage, and wherein a second one and a third one of said joints surround the one (10) of said inlet channels and the one (11) of said outlet channels, respectively, which constitute bypass channels and are closed from communication with the covered flow passage in the interspace (6), and
• further wherein leakage areas (16-19) in said interspace (6), which are situated between said first joint and the respective one of said second and third joints, communicate with the surrounding of the plate heat exchanger.