There is disclosed a refrigeration device in which a cooling capability and efficiency can be improved by controlling a high pressure side pressure of a low stage side refrigerant circuit into an optimum value. A refrigeration device 1 includes a high stage side refrigerant circuit 4, first and second low stage side refrigerant circuits 6A and 6B, and cascade heat exchangers 43A and 43B to evaporate a refrigerant of the high stage side refrigerant circuit 4, thereby cooling high pressure side refrigerants of the low stage side refrigerant circuits 6A and 6B, and carbon dioxide is charged as the refrigerant in each of the refrigerant circuits 4, 6A and 6B, and in the device, there are disposed pressure adjusting expansion valves 31 to adjust high pressure side pressures of the low stage side refrigerant circuits 6A and 6B.

Refrigeration apparatus R that includes a refrigerant circuit composed of compression section 11, gas cooler 28, electric expansion valve 39, and evaporator 41 includes: electric expansion valve 33; tank 36; split heat exchanger 29; electric expansion valve 43; electric expansion valves 47 and 71; auxiliary circuit 48, main circuit 38, and control apparatus 57, in which control apparatus 57 regulates the gas cooler outlet temperature based on outside air temperature when the outside air temperature is higher than a specified temperature, and regulates the gas cooler outlet temperature based on saturation temperature ST of saturated liquid of the refrigerant after the refrigerant flows out of compressor 11 but before flows into electric expansion valve 33, when the outside air temperature is lower than the specified temperature.

A vapor compression system that includes a reheat coil that heats a supply air stream flowing across the reheat coil with a refrigerant. A fan forces an environmental air flow across a condenser to remove energy from the refrigerant. A controller adjusts a speed of the fan to control a flow of the refrigerant through the reheat coil.

In certain embodiments, a transcritical refrigeration system provides refrigeration by circulating carbon dioxide (CO.sub.2) refrigerant through the system. A flash tank of the transcritical refrigeration system is operable to supply the CO.sub.2 refrigerant, in liquid form, to a low temperature refrigeration case and a medium temperature refrigeration case. A low temperature compressor is operable to compress the CO.sub.2 refrigerant discharged from the low temperature refrigeration case. A medium temperature compressor, a parallel compressor, and an ejector are each operable to compress the CO.sub.2 refrigerant discharged from the medium temperature refrigeration case, the CO.sub.2 refrigerant discharged from the low temperature compressor, and/or CO.sub.2 flash gas discharged from the flash tank. A gas cooler is operable to cool the CO.sub.2 refrigerant discharged from the medium temperature compressor and the parallel compressor. A controller is operable to dynamically adjust a pressure set point for the flash tank.

A vehicle air conditioning apparatus is provided that can prevent temperature variations of the air after the heat exchange in a radiator to reliably control the temperature of the air supplied to the vehicle interior. During the heating operation and the heating and dehumidifying operation, target degree of supercooling SCt when target air-blowing temperature TAO is a predetermined temperature or higher is set to SCt1 that is greater than SCt2 when the target air-blowing temperature TAO is lower than the predetermined temperature. When amount of air Ga supplied from indoor fan 12 is lower than a predetermined value, the target degree of supercooling SCt is corrected, which is set such that the degree of supercooling is lower than target degree of supercooling corrected when the amount of air Ga supplied from the indoor fan 12 is a predetermined value or higher.

A return air superheat degree test method for a multi-split system. A multi-split system comprises a re-cooling loop composed of a first heat exchanger (100) and a second heat exchanger (200), a first temperature sensor (11), a second temperature sensor (12) and a third temperature sensor (13). The return air superheat degree test method comprises the following steps: acquiring a first temperature value (T.sub.1) detected by the first temperature sensor (11), a second temperature value (T.sub.intermediate) detected by the second temperature sensor (12) and a third temperature value (T.sub.2) detected by the third temperature sensor (13); acquiring a minimum value between the first temperature value (T.sub.1) and the second temperature value (T.sub.intermediate), and acquiring a maximum value between the third temperature value (T.sub.2) and the second temperature value (T.sub.intermediate); and calculating a superheat degree according to the minimum value and the maximum value.

A vehicle air conditioning apparatus is provided that can prevent temperature variations of the air after the heat exchange in a radiator to reliably control the temperature of the air supplied to the vehicle interior. During the heating operation and the heating and dehumidifying operation, target degree of supercooling SCt when target air-blowing temperature TAO is a predetermined temperature or higher is set to SCt1 that is greater than SCt2 when the target air-blowing temperature TAO is lower than the predetermined temperature. When amount of air Ga supplied from indoor fan 12 is lower than a predetermined value, the target degree of supercooling SCt is corrected, which is set such that the degree of supercooling is lower than target degree of supercooling corrected when the amount of air Ga supplied from the indoor fan 12 is a predetermined value or higher.

A CO.sub.2 refrigeration system (1) includes: a compressor (3), a gas cooler (5), a temperature sensor (17) and an electronic control system (13), the electronic control system including a processor device (15) arranged to control operation of the compressor (3) according to input signals received from the temperature sensor (17), wherein the temperature sensor (17) is positioned to read an output temperature of the gas cooler. A method for controlling a compressor (3) in a CO.sub.2 refrigeration system (1) is also disclosed.

A method for monitoring gas pressure in a heat rejecting heat exchanger in a cooling circuit is disclosed. The present capacity of one or more compressors in the cooling circuit compared to a maximum capacity of the one or more compressors is established. If the present capacity of the one or more compressors is at least at a level corresponding to a pre-set percentage of the maximum capacity, a period of time elapsed from a point in time where the compressor capacity reached said level is established. If the established period of time has a duration which is longer than a pre-set period of time, then it is concluding that the cooling medium is in a gas loop operational mode, allowing an operator or a controller to adjust operation of the cooling plant such that the cooling medium is brought out of the gas loop operational mode.

A diagnostic monitoring system and method is employed for one or more vapor compression systems such as air conditioners and heat pumps having a compressor, an indoor air handler fan coil and an outdoor condensor. Temperature, voltage and current sensors are provided at the outdoor condensor to determine that at least one vapor compression system is operating properly. Data obtained from the sensors is wirelessly transmitted to a receiving-device for use by the systems' custodian or repair service provider and includes information concerning an occurrence of periods when one or more of the vapor compression systems are operating at an abnormal state.