The invention provides a method and apparatus for quantity controlled, continuous liquid exchange in distillation and absorption refrigerant circuits.In the method on the one hand the pressure of a volumetric liquid flow, to be supplied to the high pressure zone at a defined rate, of enriched starting solution is raised from a low level to a high pressure level, while on the other hand the mutually separated liquid flows (which in sum are equal in amount) to be removed from the high pressure zone, of the product condensate and of the depleted solution, are transferred from a high pressure level to a low pressure level. In a solution exchange apparatus the method utilizes mechanical energy of the liquid flows (which are to be depressurized and to be removed from the apparatus) and only requires a small external boosting device to overcome internal frictional and intercomponent leakage. The liquid flows that are to be depressurized are for this purpose cooled down prior to mechanical energy transfer to a value below the saturation temperature of their respective relaxation pressure level. The apparatus is a displacement apparatus. In the case of application to absorption refrigerant circuits it is preferably driven with refrigerant vapor.