Abstract: A coolant recooler (1) partially filled with a cooling fluid is cooled, in a first process step, to such a low temperature that the thus-produced and stored amount of cold is sufficient for cooling, in a subsequent process step, the coolant of a heat-producing, water-cooled apparatus (4) to be connected, during its operating period. The coolant recooler (1) is movable and connectible, for cooling purposes, to the coolant circuit of the apparatus (4). During the cooling operation, no active refrigerating machine (3) is in operation. After termination of the cooling operation, the coolant recooler (1) is uncoupled from the apparatus (4), transported away, and subsequently its cooling fluid is recooled. The amount of cold still available in each particular case is indicated by a display.