Patent ID: 7650763

Claim:
An air conditioning unit comprising: a combined refrigeration and heat pump circuit, wherein the air conditioning unit is switchably configured to change a flow direction of a refrigerant for switchable operation from the refrigeration circuit to the heat pump circuit, the refrigeration and heat pump circuit further comprising: at least a main compressor adapted for a compression of the refrigerant from a low pressure to a medium pressure in a first compression stage; a first external heat exchanger in fluid communication with the main compressor; a subsidiary compressor in fluid communication with the first external heat exchanger and adapted for a compression of the refrigerant from the medium pressure to a high pressure in a second compression stage, an inlet and an outlet of the subsidiary compressor exchanged depending on the refrigeration and heat pump circuit desired; a second external heat exchanger in fluid communication with the subsidiary compressor, wherein different pressure levels are assigned to the external heat exchangers depending on the refrigeration and heat pump circuit desired; an expansion machine in fluid communication with the second external heat exchanger, wherein the expansion machine and the subsidiary compressor form an expansion-compression machine, an inlet and an outlet of the expansion machine exchanged depending on the refrigeration and heat pump circuit desired, and wherein an assigned volume/density ratio of the compression to the expansion within the expansion-compression machine is prespecified; and an internal heat exchanger providing fluid communication between the expansion machine and the main compressor, wherein the expansion compression machine is adapted to operate in at least one of the following manners: the expansion machine is adapted to work at a full pressure and the subsidiary compressor, in addition to a displacing work, is adapted to be loaded with a volume changing work; the expansion machine is adapted to be loaded with a displacing work and a volume changing work, and the subsidiary compressor is adapted to work at the full pressure; both the expansion machine and the subsidiary compressor are adapted to work at the full pressure; and both the expansion machine and the subsidiary compressor are adapted to be loaded with a displacing work and a volume changing work.