Abstract: A refrigerator or heat pump with a jet pump (1) as the compressor, in which the evaporator (2) of the heat-pump or refrigerator circuit is incorporated in the jet pump (1). In the simplest case, this is achieved by the presence, in the inlet line, of a partition (18, 39, 40, 41) made of porous material such as, for example, sintered metal, which firstly exercises a throttling action between the condenser pressure and the evaporation pressure and secondly on whose large internal surface the evaporation of the working medium takes place at the same time. The supply of the evaporation heat is obtained by the fact that only one part of the liquid working medium fed from the condenser (3) is evaporated, and on the other hand heat can be supplied from outside via heat-exchangers (21, 27). Heat-pump or refrigerator circuits with a jet pump of this type (1, 24, 30) can also be designed with several stages, so that an internal heat exchange can be effected in a number of ways.