Abstract: The present invention concerns a plate heat exchanger for at least two heat exchanging fluids which is permanently joined with at least one sealing portion and has heat transferring plates (1-8), at least two end plates and inlet and outlet organs for the heat exchanging fluids. The core of plates includes alternating heat transferring plates (1-4) and intermediate heat transferring plates (5-8) between the alternating plates. Adjacent plates form a double wall plate unit. The plate elements are permanently joined with each other in a plurality of points having spaced apart areas. For each one of the double wall units, ridges (9) and valleys (16) on the alternating plate (1-4) are in tight contact with the corresponding ridges (9) and valleys (10) on the intermediate plates (5-8) except right at at least one of the points with the spaced apart areas.