Process and heat pump for the transfer of heat and cold

Process for the transfer of heat and cold between two separate fluid streams by means of a closed circuit of cooling medium, by which a cooling medium is successively vaporized, compressed, liquified and decompressed and, by heat exchange with the fluid streams, absorbs heat of evaporation and gives off heat of condensation, wherein (a) during heating by a condenser, said cooling medium is heated, prior to its decompression, by the Joule's heat released upon compression, and (b) prior to said heating by said Joule's heat, said cooling medium is cooled by heat exchange with the fluid stream used for vaporization, said fluid stream being simultaneously heated.