Abstract: A refrigeration system including one or more first compressor(s) for compressing a carbon dioxide (CO2) refrigerant, a main heat rejection system for cooling the CO2 refrigerant, one or more high pressure expansion device(s) for reducing the pressure of the CO2 refrigerant, a receiver for storing the CO2 refrigerant, one or more high pressure expansion device(s), an evaporator and a receiver pressure regulating device. The refrigeration system further includes an auxiliary refrigeration system including an auxiliary compressor arranged to compress at least part of the CO2 refrigerant and thereafter to direct the compressed CO2 refrigerant to a heat rejection system.

Abstract: Slush ice is produced in a liquid by adding a freezing point-depressing agent and particles to the liquid to form a liquid mix, and then cooling the liquid mix by heat exchange with a refrigeration circuit, ice crystals being formed in the liquid mix at nucleation sites provided by the particles. A slush ice of nonfrozen liquid and ice particles is produced and ice formation on the conduit in which the liquid mix flows is avoided.