The VAKATOR type heat exchanger is a welded structure with a cylindrical surface of the shell. The heat exchanger consists of an array of tubes in concentric pitch circles, two opposite tube plates, collecting and returns chambers and inlet and outlet nozzles for fluids. A constituent part of the design is to figure out different thermal dilatations of the tubes and the shell. The flow of both fluids across the exchanger is usually through more passages, with respect to pressure losses. The heat exchanger design is in a horizontal and vertical position. It is used for example as a recuperator or flue gas heat exchanger.