Abstract: The aim of the invention is to improve the performance of heat exchangers such that lost heat is discharged from a cabinet or device, whereby the rise of the inner temperature for each discharged watt of power loss is only slight. The invention also relates to a flat refrigerating set. The temperature of the heated air (SL,) can be reduced in the counterflow (L4;L3;k1;k2 . . . ) by means of counterflowing cooling air (KL) without the cooling air physically entering into contact with the heated air flow (L1,L3,L5) that is to be cooled. The air flow to be cooled (SL) can be supplied to several parallel first chambers (k1,k3,k7) via an inlet area (13). The parallel first and parallel second chambers alternate in the direction of the height or density (h) of the refrigerating unit. The alternating chambers (k1,k2,k3,k4, . . . ) also extend into a section of the flat cooling unit (l13), which is located between the inlet area (13) and a closer end (40,41) of the refrigerating unit.