Refrigeration apparatus

A refrigeration apparatus that uses a refrigerant that operates in a supercritical range, the refrigeration apparatus comprising:

• a compression mechanism having a plurality of compression elements arranged and configured so that refrigerant discharged from a first-stage compression element of the plurality of compression elements is sequentially compressed by a second-stage compression element;
• a heat source-side heat exchanger using air as a heat source and being arranged and configured to operate as a radiator or evaporator of refrigerant;
• a usage-side heat exchanger arranged and configured to operate as a evaporator or radiator of refrigerant;
• a switching mechanism arranged and configured to switch between
• a cooling operation state in which the refrigerant is circulated through the compression mechanism, the heat source-side heat exchanger, and the usage-side heat exchanger in order, and
• a heating operation state in which the refrigerant is circulated through the compression mechanism, the usage-side heat exchanger, and the heat source-side heat exchanger in order;
• and
• a second-stage injection tube arranged and configured to branch off the refrigerant, which has radiated heat in the heat source-side heat exchanger or the usage-side heat exchanger, and to return the refrigerant to the second-stage compression element
• the second-stage injection tube being arranged and configured such that refrigerant is prevented from returning to the second-stage compression element through the second-stage injection tube at least during a beginning of a reverse cycle defrosting operation, which is performed to defrost the heat source-side heat exchanger by switching the switching mechanism to the cooling operation state.