CO2 refrigeration system with superheat control

A transcritical refrigeration system, comprising:

• a gas cooler/condenser;
• a receiver configured to collect refrigerant produced by the refrigeration system and comprising a receiver outlet through which the gas refrigerant exits the receiver;
• a high-pressure control valve configured to control a flow of refrigerant from the cooler/condenser to the receiver;
• a gas bypass valve fluidly coupled to the receiver outlet and operable to control a pressure of the refrigerant in the receiver by controlling a flow of the gas refrigerant from the receiver through the gas bypass valve;
• a cooling subsystem, comprising:
• one or more expansion valves;
• one or more evaporators, at least one of the one or more evaporators comprising an evaporator outlet;
• and
• a suction group comprising one or more transcritical compressors operable to compress gas refrigerant and discharge the compressed gas refrigerant into a discharge line;
• a superheat control system, comprising:
• at least one heat exchanger comprising a first side configured to carry gas refrigerant passing between the gas cooler/condenser and an inlet of the high-pressure control valve;
• and a second side in heat transfer communication with the first side and comprising a second side inlet and a second side outlet, the second side inlet in being in fluid communication with, and at substantially the same operating pressure as, the evaporator outlet of at least one the evaporators;
• a valve system comprising one or more valves, the valve system configured to route gas refrigerant from the evaporator outlet of the at least one evaporator such that at least a portion of the gas refrigerant from the evaporator outlet passes through the second side of the heat exchanger and to a suction input of at least one of the one or more transcritical compressors of the suction group, the one or more valves comprising a three-way valve configured to control a flow of the gas refrigerant through the second side of the heat exchanger, the three-way valve comprising:
• a first inlet fluidly coupled to the second side inlet of the heat exchanger,
• a second inlet fluidly coupled to the second side outlet of the heat exchanger, and
• a common outlet fluidly coupled to the suction input of the one or more transcritical compressors;
• and
• a controller configured to perform operations comprising:
• determining that one or more first operating parameters are within a first operating range;
• and
• in response to a determination that the one or more first operating parameters are within the first operating range, modulating the three-way valve of the valve system to control a flow of gas refrigerant from the evaporator outlet to the inlet of the second side.

A method of operating a transcritical refrigeration system, comprising:

• compressing a refrigerant in one in one or more transcritical compressors in a suction group of the transcritical refrigeration system;
• circulating the refrigerant from an outlet of at least one of the one or more transcritical compressors through a gas cooler/condenser;
• circulating the refrigerant from an outlet of gas cooler/condenser through a first side of a heat exchanger;
• collecting a portion of the refrigerant from an outlet of the first side of the heat exchanger into a receiver;
• controlling a pressure of the refrigerant in the receiver by controlling a flow of gas refrigerant from the receiver through a gas bypass valve;
• circulating liquid refrigerant from the receiver through one or more evaporators in a cooling subsystem of the refrigeration system;
• circulating the refrigerant from an evaporator outlet of at least one of the evaporators through a second side of the heat exchanger such that heat is transferred from the refrigerant in the first side of the heat exchanger to refrigerant in the second side of the heat exchanger;
• circulating at least a portion of the refrigerant from the second side of the heat exchanger to a suction input of at least one of the one or more transcritical compressors;
• and
• controlling a three-way valve to modulate a flow of refrigerant through the second side of the heat exchanger, the three-way valve comprising:
• a first inlet fluidly coupled to a second side inlet of the second side of the heat exchanger,
• a second inlet fluidly coupled to a second side outlet of the second side of the heat exchanger, and
• a common outlet fluidly coupled to the suction input of the one or more transcritical compressors.