Abstract: A refrigeration apparatus (1) is disclosed which is provided with multiple systems of utilization-side heat exchangers (20, 30, 40) and in which liquid-side interunit piping lines (53, 54, 55) are combined into a single liquid-side interunit piping line in multiple systems of liquid lines. When the refrigeration apparatus (1) provides space heating of 100% heat recovery without the use of an outdoor heat exchanger (15), the flow of refrigerant in a refrigerant circuit (50) is stabilized even when the temperature of outside air is low, thereby preventing the capacity to provide refrigeration from decreasing.

Abstract: In a refrigerant circuit (20), an air conditioning unit (12), a cold-storage showcase (13), and a freeze-storage showcase (14) are connected in parallel to an outdoor unit (11). When placing an indoor heat exchanger (71) of the air conditioning unit (12) in the thermo-off state, a degree-of-opening control means (101) provides control so that an indoor expansion valve (72) is placed in the fully closed state. Thereafter, the degree-of-opening control means (101) detects the accumulated amount of refrigerant within the indoor heat exchanger (71) and then adjusts the degree of opening of the indoor expansion valve (72) depending on the refrigerant amount detected.

Abstract: A refrigerant return mechanism (5) is provided for returning liquid refrigerant in a receiver (17) to a circulation path. Whereby, the liquid refrigerant in the receiver (17) is forcedly returned to the circulation path in an operation state where the circulation path is formed in which the refrigerant sent out from compression mechanism (11D, 11E) flows from a second user side unit (20) to first user side units (30, 40) and is then returned to the compression mechanisms (11D, 11E).

Abstract: A refrigerant circuit (20) includes a low stage compressor (101, 102, 121, 122), a high stage compressor (41, 42, 43), an outdoor heat exchanger (44) and a utilization side heat exchanger (83, 93). During a defrosting operation of the refrigeration system (10), the high stage compressor (41, 42, 43) is driven. Refrigerant discharged from the high stage compressor (41, 42, 43) is pumped into the utilization side heat exchanger (83, 93) to heat frost on it from its inside. Thereafter, the refrigerant evaporates in the outdoor heat exchanger (44), is then compressed by the high stage compressor (41, 42, 43) and is sent again to the utilization side heat exchanger (83, 93).

Abstract: In order that an indoor heat exchanger (41), a cold storage heat exchanger (45), and a freeze storage heat exchanger (51) may differ in their refrigerant evaporating temperature, a refrigerant circuit (1E) is provided with a suction side three way switching valve (102) capable of switching of flow paths between the heat exchangers (41, 45, 51) and a compressor (2).

Abstract: A subcooling unit (200) includes a refrigerant passage (205) connected to liquid side communication pipes (21, 22) of a refrigerating apparatus (10). When a subcooling compressor (221) is operated, subcooling refrigerant circulates in a subcooling refrigerant circuit (220) to perform a refrigeration cycle, thereby cooling refrigerant of the refrigerating apparatus (10) which flows in the refrigerant passage (205). A controller (240) of the subcooling unit (200) receives the detection value of an outside air temperature sensor (231) or a refrigerant temperature sensor (236). The controller (240) controls the operation of the subcooling compressor (221) with the use of only information obtainable within the subcooling unit (200).

Abstract: An outside air temperature sensor (231) for detecting the temperature of outside air, and a control means (240) for controlling the operating capacity of a supercool compressor (221) are provided. The control means (240) controls the operation of the supercool compressor (221) based on the state of refrigerant of a refrigerant circuit (20) flowing through a supercool heat exchanger (210) and the temperature of outside air detected by the outside air temperature sensor (231).

Abstract: The loss of refrigerant pressure which is caused in a return-side interconnecting piping line (19) comprising return-side interconnecting piping lines respectively extending from outlet ports (24, 34, 44) of single-stage side utilization units (12, 13, 14) to an inlet port (61) of a heat source unit (11) is set such that the lowest valued refrigerant pressure loss is caused by a said return-side interconnecting piping line of the return-side interconnecting piping line (19) that is connected to the lowest of the single-stage side utilization units (12, 13, 14) in compartment preset temperature.

Abstract: A pressure regulating valve (71) is connected to the discharge side of a low stage compressor (55) to make the pressure in the suction side of high stage compressors (11, 12) lower than the pressure in a dome of the low stage compressor (55). Further, an oil return path (72) is connected to the dome of the low stage compressor (55) at one end and to the suction side of the high stage compressors (11, 12) by bypassing the pressure regulating valve (71) at the other end. With this configuration, refrigeration oil accumulated in the dome of the low stage compressor (55) is returned to the high stage compressors (11, 12).

Abstract: A refrigerator circuit (110) and a freezing circuit (30) are connected to an outdoor circuit (40) in parallel in a refrigerant circuit (20), and a freezer circuit (130) and a booster circuit (140) are connected in series in the freezing circuit (30). The booster circuit (140) includes a booster compressor (141) and three-way switching mechanisms (142, 160). During cooling operation of a freezing heat exchanger (131), first operation is performed in the three-way switching mechanisms (142, 160) so that the refrigerant evaporated in the freezing heat exchanger (131) is compressed in the booster compressor (141) and is sucked into a variable capacity compressor (41).

Abstract: A subcooling unit (200) includes a refrigerant passage (205) connected to liquid side communication pipes (21, 22) of a refrigerating apparatus (10). When a subcooling compressor (221) is operated, subcooling refrigerant circulates in the subcooling refrigerant circuit (220) to perform a refrigeration cycle, thereby cooling refrigerant of the refrigerating apparatus (10) which flows in the refrigerant passage (205). A controller (240) of the subcooling unit (200) receives the detection value of a suction pressure sensor (234) and a refrigerant temperature sensor (236). The controller (240) utilizes input signals from the sensors (234, 236) to control driving operation of the subcooling compressor (221) on the basis of information obtained within the subcooling unit (200). Thus, the operation of the subcooling compressor (221) can be controlled without sending and receiving a singal to and from the refrigerating apparatus (10) to which the subcooling unit (200) is incorporated.