Method for controlling a temperature distribution in a heat exchanger

Device comprising:

• a heat exchanger,
• at least one optical waveguide arranged in the heat exchanger for measuring an actual temperature distribution in the heat exchanger, and
• a measuring device connected to the at least one optical waveguide, which device is designed for launching light into the at least one optical waveguide and evaluating light scattered in the at least one optical waveguide for determining the actual temperature distribution, and
• the device having a control means for controlling at least one flow of a fluid medium carried in the heat exchanger in such a way that the actual temperature distribution is made to approximate a target temperature distribution;
• characterized in that the heat exchanger has a tube bundle with a multiplicity of tubes, which are arranged in a shell space of the heat exchanger, the at least one optical waveguide being arranged in the interior space of a tube of the heat exchanger in the shell space.