Method for operating a heat exchanger, arrangement with a heat exchanger, and system with a corresponding arrangement

The invention relates to a method for operating a heat exchanger (1), in which a first operating mode is carried out in first time periods, and a second operating mode is carried out in second time periods that alternate with the first time periods; in the first operating mode a first fluid flow (A) is formed at a first temperature level, is fed into the heat exchanger (1) in a first region (2) at the first temperature level, and is partially or completely cooled in the heat exchanger (1); in the first operating mode a second fluid flow (B) is formed at a second temperature level, is fed into the heat exchanger (1) in a second region (3) at the second temperature level, and is partially or completely heated in the heat exchanger (1); and in the second operating mode the feeding of the first fluid flow (A) and of the second fluid flow (B) into the heat exchanger (1) is partially or completely halted. In the second time period the second region (12) is cooled by using cooling fluid that is conducted through passages in or on the heat exchanger (1) in the second region (12) but not in the first region (11) which comprises the terminal 30% at the warm end of the heat exchanger (1). A corresponding arrangement (10) and a system (100) with such an arrangement (10) are also covered by the present invention.