A heat exchanger, which comprises - a plate pack formed of circular heat exchange plates having openings and arranged on top of each other, in which plate pack the heat exchange plates are attached to each other as plate pairs, the inner parts of which plate pairs are arranged in connection with each other via flow channels formed by the openings of the heat exchange plates, - an outer casing surrounding the plate pack, which casing comprises end plates mainly in the direction of the ends of the plate pack and a cylindrical shell connecting the end plates, - inlet and outlet connections (5a, 5b) for a first heat exchange medium arranged through the end plate of the outer casing, which connections (5a, 5b) are arranged in connection with the inner parts of the plate pairs of the plate pack, and - inlet and outlet connections (6a, 6b) for a second heat exchange medium arranged through the outer casing, which connections (6a, 6b) are arranged in connection with the inside of the outer casing, i.e. with the outside of the plate pack, and - the plate pack is arranged inside the shell in an acentric manner, so that the midpoint of the cross-section of the plate pack substantially deviates from the midpoint of the cross-section of the shell in the vertical direction and/or lateral direction of the cross-section, whereby the distance of the outer surface of the plate pack defined by the outer edges of the heat exchange plates from the inner surface of the shell is substantially different on opposite outer edges of the plate pack, characterised in that - the inlet and outlet connections (6a, 6b) for the second heat exchange medium are arranged through the end plate of the outer casing, so that the connection (6a, 6b) opens into a space between the outer surface of the plate pack and the inner surface of the shell where the plate pack is farthest from the inner surface of the shell. - a plate pack formed of circular heat exchange plates having openings and arranged on top of each other, in which plate pack the heat exchange plates are attached to each other as plate pairs, the inner parts of which plate pairs are arranged in connection with each other via flow channels formed by the openings of the heat exchange plates, - an outer casing surrounding the plate pack, which casing comprises end plates mainly in the direction of the ends of the plate pack and a cylindrical shell connecting the end plates, - inlet and outlet connections (5a, 5b) for a first heat exchange medium arranged through the end plate of the outer casing, which connections (5a, 5b) are arranged in connection with the inner parts of the plate pairs of the plate pack, and - inlet and outlet connections (6a, 6b) for a second heat exchange medium arranged through the outer casing, which connections (6a, 6b) are arranged in connection with the inside of the outer casing, i.e. with the outside of the plate pack, and - the plate pack is arranged inside the shell in an acentric manner, so that the midpoint of the cross-section of the plate pack substantially deviates from the midpoint of the cross-section of the shell in the vertical direction and/or lateral direction of the cross-section, whereby the distance of the outer surface of the plate pack defined by the outer edges of the heat exchange plates from the inner surface of the shell is substantially different on opposite outer edges of the plate pack, characterised in that - the inlet and outlet connections (6a, 6b) for the second heat exchange medium are arranged through the end plate of the outer casing, so that the connection (6a, 6b) opens into a space between the outer surface of the plate pack and the inner surface of the shell where the plate pack is farthest from the inner surface of the shell.