Abstract: A process using a liquid transfer fluid whose triple point temperature is less than ?125° C., such as isopentane, in order to recover cold energy of sublimating and melting substances frosted on exchanger surfaces and more particularly CO2. The same transfer fluid circulates on two coupled circuits, one purely refrigerating, the other heat transferring, when it carries out defrosting operations, and refrigerating to transfer refrigerating power recovered during the defrosting operations.