Refrigeration system and method

A carbon dioxide (CO2) refrigeration system including:

• a CO2-based refrigerant circuit including a refrigerant compression device, a refrigerant cooling heat exchanger for passing refrigerant received from said compression device at a high pressure in heat exchange relationship with a cooling medium, a refrigerant heating heat exchanger for passing refrigerant at a low pressure in heat exchange relationship with a heating medium of the refrigerant heating heat exchanger, and an expansion device disposed in the CO2-based refrigerant circuit downstream of said refrigerant cooling heat exchanger and upstream of said refrigerant heating heat exchanger;
• a flash tank receiver disposed in the CO2-based refrigerant circuit downstream of said refrigerant cooling heat exchanger and upstream of said expansion device, the flash tank receiver configured to separate refrigerant from the refrigerant cooling heat exchanger into gas refrigerant and liquid refrigerant;
• at least one ejector disposed in the CO2-based refrigerant circuit downstream of said refrigerant cooling heat exchanger and upstream of said flash tank receiver;
• a three-way valve disposed at an entry side of the refrigerant compression device and configured to transition the mode of operation of the refrigeration system between:
• a first mode in which the flash tank receiver receives refrigerant exclusively from the refrigerant cooling heat exchanger, and gas refrigerant from the flash tank receiver is caused to pass through a first refrigerant line from the flash tank receiver to the refrigerant compression device such that refrigerant passing from the refrigerant heating heat exchanger to the refrigerant compression device is blended with said vapour refrigerant from the flash tank;
• a second mode in which the gas refrigerant from the flash tank receiver is caused to pass through a second refrigerant line from the flash tank receiver to the refrigerant compression device such that the refrigerant compression device is supplied refrigerant exclusively from the flash tank receiver, wherein refrigerant from the refrigerant heating heat exchanger is diverted through a third refrigerant line to the at least one ejector where the refrigerant is blended with refrigerant from the refrigerant cooling heat exchanger, the flash tank receiver thereby receiving a mix of refrigerants from the refrigerant heating heat exchanger and the refrigerant cooling heat exchanger;
• and
• a controller operatively associated with the three-way valve, the controller configured to automatically activate or schedule the activation of the three-way valve, to thereby cause the refrigeration system to transition directly from the first to the second mode of operation, upon determining a particular condition, the particular condition including one or more of:
• a dry-bulb ambient temperature increasing from a first temperature below approximately 25 degrees Celsius to a second temperature equal to or greater than approximately 25 degrees Celsius, and
• a temperature at a discharge of the refrigerant cooling heat exchanger increasing from a first temperature below approximately 27 degrees Celsius to a second temperature equal to or greater than approximately 27 degrees Celsius.