A Plate and Shell type plate heat exchanger, which comprises a plate pack, a shell surrounding the plate pack, and end plates mainly in the direction of the ends of the plate pack and inlet and outlet connections for a first heat exchange medium and a second heat exchange medium arranged through the end plate. The plate pack of the heat exchanger is arranged inside the shell in an acentric manner, so that the midpoint of the cross-section of the plate pack deviates substantially from the midpoint of the cross-section of the shell in the vertical direction and/or lateral direction of the cross-section.