Patent ID: 9664424
Date: 2017-05-30
CPC Classifications: F25B

Claim:
1. A cascade refrigeration system, comprising: a primary portion having at least one modular chiller unit, the primary portion being configured to provides cooling to at least one of a low temperature subsystem having a plurality of low temperature loads, and a medium temperature subsystem having a plurality of medium temperature loads; the modular chiller unit comprising: a refrigerant circuit having at least a compressor, a condenser, an expansion device, and an evaporator; an ammonia refrigerant configured for circulation within the refrigerant circuit; an ammonia refrigerant accumulator configured to transmit the ammonia refrigerant to the evaporator, to separately receive the ammonia refrigerant from the evaporator, and to receive the ammonia refrigerant from the condenser separate from the ammonia refrigerant received from the evaporator; and an oil management system downstream of the compressor and configured to remove oil from the ammonia refrigerant, the oil management system having an oil separator disposed between the compressor and the condenser, the oil separator configured to provide oil to an oil reservoir separate from the ammonia refrigerant accumulator, the oil reservoir coupled to the compressor via a pressure regulator, and an oil return line coupled to the evaporator and the ammonia refrigerant accumulator, the oil return line configured to receive oil returned from the evaporator and to provide the oil returned from the evaporator to the accumulator; wherein the pressure regulator is configured to provide oil to the compressor from the oil reservoir to maintain a target pressure in the oil reservoir.