Refrigeration system and method of defrosting the same

A method of operating a refrigeration system, the method comprising:

• operating a first low-temperature evaporator in a refrigeration mode, wherein the first low-temperature evaporator receives refrigerant from a flash tank;
• operating a second low-temperature evaporator in the refrigeration mode, wherein the first second low-temperature evaporator receives refrigerant from the flash tank;
• and
• causing the first low-temperature evaporator to operate in a defrost mode by:
• closing a first controllable valve in a refrigerant conduit that couples the first low-temperature evaporator to a low-temperature compressor of the refrigeration system;
• and
• directing the refrigerant exiting the first low-temperature evaporator to be received by the second low-temperature evaporator,
• wherein operating the first low-temperature evaporator in the defrost mode further comprises:
• opening a first expansion valve positioned in the refrigerant conduit, wherein the first expansion valve is located between the flash tank and the first low-temperature evaporator, and wherein opening the first expansion valve increases a fraction of liquid refrigerant that is received by the first low-temperature evaporator during the defrost mode relative to the refrigeration mode of the first low-temperature evaporator;
• and
• directing the refrigerant exiting the first low-temperature evaporator to a second expansion valve positioned between the flash tank and the second low-temperature evaporator.

A controller of a refrigeration system, the controller comprising:

• a network interface circuit communicatively coupled to a first controllable valve positioned in a refrigerant conduit and downstream from a first low-temperature evaporator, the first controllable valve configured control refrigerant from the first low-temperature evaporator and direct a flow of the controlled refrigerant to:
• (i) a low-temperature compressor when the first controllable valve is configured in an open position;
• and (ii) a second low-temperature evaporator when the first controllable valve is configured in a closed position;
• and
• a processor operably coupled to the network interface circuit and configured to:
• cause the first low-temperature evaporator to operate in a defrost mode by closing the first controllable valve to direct the refrigerant exiting the first low-temperature evaporator to be received by the second low-temperature evaporator,
• wherein the controller is further configured to cause the first low-temperature evaporator to operate in the defrost mode by:
• opening a first expansion valve positioned in the refrigerant conduit, wherein the first expansion valve is located between a flash tank and the first low-temperature evaporator, and wherein opening the first expansion valve increases a fraction of liquid refrigerant that is received by the first low-temperature evaporator during the defrost mode relative to a refrigeration mode of the first low-temperature evaporator;
• and
• directing the refrigerant exiting the first low-temperature evaporator to a second expansion valve positioned between the flash tank and the second low-temperature evaporator.