Refrigeration apparatus controlling opening degree of a second expansion mechanism based on air temperature at the evaporator or refergerant temperature at the outlet of a two stage compression element

A refrigerating apparatus where a working refrigerant reaches a supercritical state in at least part of a refrigeration cycle, the refrigerating apparatus comprising:

• a first expansion mechanism arranged and configured to reduce pressure of refrigerant;
• a second expansion mechanism arranged and configured to reduce pressure of refrigerant;
• an evaporator connected to the first expansion mechanism, the evaporator being arranged and configured to evaporate refrigerant;
• a first compression element arranged and configured to suck in, compress and discharge refrigerant;
• a second compression element arranged and configured to suck in, further compress and discharge refrigerant that has been discharged from the first compression element;
• a third refrigerant pipe arranged and configured to allow refrigerant that has been discharged from the first compression element to be sucked into the second compression element;
• a radiator connected to a discharge side of the second compression element;
• a first refrigerant pipe interconnecting the radiator and the first expansion mechanism;
• a fourth refrigerant pipe branching from the first refrigerant pipe and extending to the second expansion mechanism;
• a fifth refrigerant pipe extending from the second expansion mechanism to the third refrigerant pipe;
• a second heat exchanger arranged and configured to cause heat exchange to be performed between refrigerant flowing through the first refrigerant pipe and refrigerant flowing through the fifth refrigerant pipe;
• a temperature detector arranged and configured to detect a value of at least either one of
• a temperature of air around the evaporator, and
• a temperature of refrigerant discharged from at least either one of the first compression element and the second compression element;
• a controller configured to control the second expansion mechanism to increase a quantity of the refrigerant passing therethrough
• when the value detected by the temperature detector is temperature of air, and the air temperature is lower than a predetermined tow-temperature air temperature, or
• when the value detected by the temperature detector is temperature of refrigerant, and the refrigerant temperature is higher than a predetermined high-temperature refrigerant temperature;
• an external cooler arranged and configured to cool refrigerant passing through the third refrigerant pipe;
• an external temperature detector arranged and configured to detect a temperature of a fluid passing through the external cooler;
• and
• a third refrigerant temperature detector arranged and configured to detect a temperature of refrigerant passing through the third refrigerant pipe,
• the controller being further configured to control the second expansion mechanism to increase the quantity of the refrigerant passing therethrough when a difference between the temperature detected by the external temperature detector and the temperature detected by the third refrigerant temperature detector has become less than a predetermined value.