Abstract: A refrigeration system (1) includes first to third compressors (11a, 11b, 11c) connected in parallel and an oil separator for separating a refrigeration oil from a refrigerant discharged from the compressors (11a, 11b, 11c). A main suction pipe (55) in which a refrigerant to be sucked into the compressors (11a, 11b, 11c) flows includes a primary curved portion (101) and a primary branch element (102) assembled to part of the main suction pipe (55) downstream of a junction with an oil return pipe (71) for returning the refrigeration oil separated by the oil separator. The main suction pipe (55) is branched by the primary branch element (102) into a first suction pipe branch (61a) of the first compressor (11a) and a connecting suction pipe (56). In the primary branch element (102), the first suction pipe branch (61a) is at the bottommost position and the outermost position in the direction of a radius of curvature of the primary curved portion (101).

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: 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: 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.