REFRIGERATION UNIT

摘要

In a refrigerant circuit (20), a variable capacity compressor (40a) sucks a refrigerant from a first suction pipe (51), and a second fixed capacity compressor (40c) sucks a refrigerant from a third suction pipe (53). Refrigerant oil of each oil separator (47a to 47c) is introduced to each compressor (40a to 40c) along with an intermediate pressure refrigerant, through an oil returning pipe (54) and a main injection pipeline (61). A controller (200) adjusts the opening of each motor-operated injection valve (64a to 64c) so that the temperature of a discharge refrigerant of the corresponding compressor reaches a predetermined target value, when the controller is normally operated. Further, when the pressure of the first suction pipe (51) is lower than that of the third suction pipe (53), the controller temporally reduces the opening of the first motor-operated injection valve (64a), and increases the opening of the third motor-operated injection valve (64c), in comparison with the openings thereof obtained when the controller is normally operated. As a result, the flow rates of the intermediate pressure refrigerant and the refrigerant oil, which are introduced to the second fixed capacity compressor (40c), are increased.