Plate heat exchanger consisting of at least two modules (1a, 1b), • wherein each module (1a, 1b) has a multiplicity of passages which are arranged in a stack-shaped manner, and through which heat-exchanging media can flow in an alternating manner and which is separated from one another by separating plates, • the modules (1a, 1b) are overall cuboidal and are bounded on the outer sides by cover plates, • the modules (1a, 1b) are arranged next to each other in such a manner that a rectangular side of one cuboidal module is directly adjacent to a corresponding rectangular side of another cuboidal module, • the modules (1a, 1b) have means for supplying and removing the heat-exchanging media and means (headers) for distributing and collecting the heat-exchanging media to and from the individual passages, and • wherein at least two modules (1a, 1b) have at least one common header, characterized in that • at least one moulded part (20a, 20b, 30a, 30b, 40a, 40b, 60a, 60b) is fastened in each case on the two cover plates which form the respectively directly adjacent sides (9a, 9b) of two adjacent modules (1a, 1b), referred to below as contact surfaces (9a, 9b), wherein • the moulded parts (40a, 40b, 60a, 60b) are arranged and shaped in such a manner that the movement of the modules (1a, 1b) perpendicularly to the contact surface (9a, 9b) is prevented by at least one moulded part (40a, 60a) on one contact surface and a moulded part (40b, 60b) on the other contact surface, or • the moulded parts (20a, 20b, 30a, 30b) are arranged and shaped in such a manner that the movement of the modules (1a, 1b) perpendicularly to the contact surface (9a, 9b) is prevented by at least one moulded part (20a, 30a) on one contact surface and a moulded part (20b, 30b) on the other contact surface and by at least one additional moulded part (50, 51). • wherein each module (1a, 1b) has a multiplicity of passages which are arranged in a stack-shaped manner, and through which heat-exchanging media can flow in an alternating manner and which is separated from one another by separating plates, • the modules (1a, 1b) are overall cuboidal and are bounded on the outer sides by cover plates, • the modules (1a, 1b) are arranged next to each other in such a manner that a rectangular side of one cuboidal module is directly adjacent to a corresponding rectangular side of another cuboidal module, • the modules (1a, 1b) have means for supplying and removing the heat-exchanging media and means (headers) for distributing and collecting the heat-exchanging media to and from the individual passages, and • wherein at least two modules (1a, 1b) have at least one common header, characterized in that • at least one moulded part (20a, 20b, 30a, 30b, 40a, 40b, 60a, 60b) is fastened in each case on the two cover plates which form the respectively directly adjacent sides (9a, 9b) of two adjacent modules (1a, 1b), referred to below as contact surfaces (9a, 9b), wherein • the moulded parts (40a, 40b, 60a, 60b) are arranged and shaped in such a manner that the movement of the modules (1a, 1b) perpendicularly to the contact surface (9a, 9b) is prevented by at least one moulded part (40a, 60a) on one contact surface and a moulded part (40b, 60b) on the other contact surface, or • the moulded parts (20a, 20b, 30a, 30b) are arranged and shaped in such a manner that the movement of the modules (1a, 1b) perpendicularly to the contact surface (9a, 9b) is prevented by at least one moulded part (20a, 30a) on one contact surface and a moulded part (20b, 30b) on the other contact surface and by at least one additional moulded part (50, 51).