The present invention concerns among other things a plate heat exchanger for at least two heat exchanging fluids which heat exchanger is permanenty joined with at least one sealing means and comprises at least one core of plates with heat transferring plates (1-8), at least two end plates as well as inlet organs 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. Each one of the said alternating heat transferring plates (1-4) and a second one of the said two respective adjacent intermediate plates (5-8) form a double wall unit. For each one of the said double wall units ridges (9) and valleys (10) on the said alternating plate (1-4) are in all of their respective areal extensions adapted to and in near contact with the corresponding ridges (9) and valleys (10) on the said intermediate plate (5-8) except right before each one of at least one of those points with the closest around situated areas where the ridges (9) and valley (10) on a double wall unit are in contact with ridges (9) and valleys (10) on another double wall unit in the core of plates.
